BAS20@215 - NXP SEMICONDUCTORS - Datasheet.Directory

Rev 1 January 2006 www.semtech.com

XE8805/05A Sensing Machine

Data Acquisition MCU

with Zoomin

ADC and DACs

XE8805/05A – SX8805R Sensing

Machine – Data Acquisition with 16+10 bit

ZoomingADC™ and buffered DACs

General Description

The XE8805A is a data acquisition ultra low-

power low-voltage system on a chip (SoC) with a

high efficiency microcontroller unit embedded

(MCU), allowing for 1 MIPS at 300uA and 2.4 V,

and multiplying in one clock cycle.

The XE8805A includes a high resolution

acquisition path with the 16+10 bits ZoomingADC

and two buffered DACs.

The XE8805A is available with on chip ROM (the

SX8805) or Multiple-Time-Programmable (MTP)

program memory.

Applications

• Portable, battery operated instruments

• Current loop powered instruments

• Wheatstone bridge interfaces

• Pressure and chemical sen sors

• HVAC control

• Metering

• Sports watches, wrist instruments

Key product Features

• Low-power, high resolution ZoomingADC

• 0.5 to 1000 gain with offset cancellation

• up to 16 bits analog to digital converter

• up to 13 inputs multiplexer

• Low-voltage low-power controller operation

• 2 MIPS with 2.4 V to 5.5 V operation

• 300 µA at 1 MIPS over voltage range

• 22 kByte (8 kInstruction) MTP

• 520 Byte RAM data memory

• RC and crystal oscillators

• 5 reset, 22 interrupt, 8 event sources

• 8 bit and 16 bit buffered DACs

• 100 years MTP Flash retention at 55°C

Ordering Information

Product Temperature range Memory type Package

XE8805MI028* -40°C to 85 °C MTP LQFP64

XE8805AMI000 -40°C to 85 °C MTP die

XE8805AMI028LF -40°C to 85 °C MTP LQFP64

SX8805Rxxx -40°C to 85 °C** ROM

*Not for new designs

**Extended temperature range on request

XE8805/05A Sensing Machine

Data Acquisition MCU

with Zoomin

ADC and DACs

TABLE OF CONTENTS

Chapter 1 XE8805/05A Overview

Chapter 2 XE8805/05A Performance

Chapter 3 XE8805/05A CPU

Chapter 4 XE8805/05A Memory

Chapter 5 System Block

Chapter 6 Reset generator

Chapter 7 Clock generation

Chapter 8 Interrupt handler

Chapter 9 Event handler

Chapter 10 Low power RAM

Chapter 11 Port A

Chapter 12 Port B

Chapter 13 Port C

Chapter 14 Universal Asynchron ous Receiver/Transmitter (UART)

Chapter 15 Universal Synchronous Receiver/Tra nsmitter (USRT)

Chapter 16 Acquisition Chain (ZoomingADC™)

Chapter 17 Voltage multiplier

Chapter 18 Signal D/A (DAS)

Chapter 19 Bias D/A (DAB)

Chapter 20 Counters/Timers/PWM

Chapter 21 The Voltage Level Detector

Chapter 22 XE8805/05A Dimensions

1-1

XE8805/05A

1. General overview

CONTENTS

1.1 Top schematic 1-2

1.1.1 General description 1-2

1.1.2 XE8805 vs XE8805A 1-4

1.2 Pin map 1-4

1.2.1 Bare die 1-4

1.2.2 LQFP-64 1-5

1.3 Pin assignment 1-6

1-2

XE8805/05A

1.1 Top schematic

1.1.1 General description

The top level block schematic of the circuit is shown in Figure 1-1. The heart of the circuit consists of the

Coolrisc816® CPU core. This core includes an 8x8 multiplier and 16 internal registers.

The bus controller generates all control signals for access to all data registers other than the CPU internal

registers.

The reset block generates the adequate reset signals for the rest of the circuit as a function of the set-up contained

in its control registers. Possible reset sources are the power-on-reset (POR), the external pin RESET, the

watchdog (WD), a bus error detected by the bus controller or a programmable pattern on Port A. Different low

power modes are implemented.

The clock generation and power management block sets up the clock signals and generates internal supplies for

different blocks. The clock can be generated from the RC oscillator (this is the start-up condition), the crystal

oscillator (XTAL) or an external clock source (given on the OSCIN pin).

The test controller generates all set-up signals for different test modes. In normal operation, it is used as a set of 8

low power data registers. If power consumption is important for the application, the variables that need to be

accessed very often should be stored in these registers rather than in the RAM.

The IRQ handler routes the interrupt signals of the different peripherals to the IRQ inputs of the CPU core. It allows

masking of the interrupt sources and it flags which interrupt source is active.

Events are generally used to restart the processor after a HALT period without jumping to a specified address, i.e.

the program execution resumes with the instruction following the HALT instruction. The EVN handler routes the

event signals of the different peripherals to the EVN inputs of the CPU core. It allows masking of the interrupt

sources and it flags which interrupt source is active.

The Port B is an 8 bit parallel IO port with analog capabilities. The URST, UART, and PWM block also make use of

this port.

The instruction memory is a 22-bit wide flash or ROM memory depending on the circuit version. Flash and ROM

versions have both 8k instruction memory. The data memory of this product is 512 byte SRAM.

The Acquisition Chain is a high resolution acquisition path with the 16+10 bit fully differential ZoomingADC™. The

VMULT (voltage multiplier) powers a part of the Acquisition Chain.

The signal D/A (DAS) is a 16 bit D/A based on sigma-delta modulation. It includes a stand-alone amplifier that can

be used for analog output filtering.

The bias D/A (DAB) is an 8 bit low frequency D/A. It includes a stand-alone amplifier that is used to drive large

currents. It can be used to bias a sensor.

The Port A is an 8 bit parallel input port. It can also generate interrupts, events or a reset. It can be used to input

external clocks for the timer/counter/PWM block.

The Port C is a general purpose 8 bit parallel I/O port.

The USRT (universal synchronous receiver/transmitter) contains some simple hardware functions in order to

simplify the software implementation of a synchronous serial link.

1-3

XE8805/05A

INSTRUCTION MEM ORY

TEST CON TROLLER

RESET BLOCK

CLOCK

GENERATION/

POWER

MANAGEMENT

VREG

XTAL

CPU

COO LRISC816

8X8 MULTIPLIER

16 CPU REGISTERS

IRQ HANDLING

EVN HANDLING

PORT B

8 DAT A R EG IST ERS

PORT A

PORT C

address

control

datain

data o u t

reset

control

clocks

tes t

control

irq

evn

VPP/TEST

VBAT

VSS

RESET

OSCIN

OSCOUT

VREG

PB(7:0)

PA(7:0)

PC(7:0)

A C_R (3:0)

AC_A(7:0)

VMULT

DAS_OUT

DAS_AI_P

DAS_AI_M

DAS_AO

DAB_R_P

DAB_R_M

DAB_OUT

DAB_AI_P

DAB_AI_M

DAB_AO_P

DAB_AO_M

DATA

MEMORY

VLD

USRT

UART

COUNTERS

TIMERS

PWM

PB(5:4) PB(7:6) PA(3:0) PB(1:0)

POR

AC QUIS IT IO N

CHAIN

ZoomingADCTM

VMULT

DAS

Signal D/A

DAB

Bias D/A

Figure 1-1. Block schematic of the XE8805/05A circuit.

The UART (universal asynchronous receiver/transmitter) contains a full hardware implementation of the

asynchronous serial link.

The counters/timers/PWM can take their clocks from internal or external sources (on Port A) and can generate

interrupts or events. The PWM is output on Port B.

1-4

XE8805/05A

The VLD (voltage level detector) detects the battery end of life with respect to a programmable threshold.

1.1.2 XE8805 vs XE8805A

The XE8805A has a new RESET pin function. The action of the RESET pin of the XE8805A resets the clock

registers too and creates an additional short delay. See the RESET chapter for more information.

1.2 Pin map

1.2.1 Bare die

(52.6,4123.5) PA(0)

(52.6, 3908.5) PA(1)

(52.6,3693.5) PA(2)

(52.6, 3478.5) PA(3)

(52.6, 3263.5) VBAT

(52.6, 3048.5) PA(4)

(52.6, 2833.5) PA(5)

(52.6, 2618.5) PA(6)

(52.6, 2403.5) PA(7)

(52.6, 2188.5) PC(0)

(52.6, 1973.5) PC(1)

(52.6, 1758.5) PC(2)

(52.6, 1543.5) PC(3)

(52.6, 1328.5) VSS

(52.6, 1113.5) PC(4)

(52.6, 898.5) PC(5)

(52.6, 683.5) PC(6)

(52.6, 468.5) PC(7)

AC_R(0) (3958.4, 4118.5)

AC_R(1) (3958.4, 3858.5)

VSS (3958.4, 3603.5)

AC_A(0) (3958.4, 3343.5)

AC_A(1) (3958.4, 3088.5)

AC_A(2) (3958.4, 2828.5)

AC_A(3) (3958.4, 2573.5)

AC_A(4) (3958.4, 2313.5)

VBAT (3958.4, 2058.5)

AC_A(5) (3958.4,1798.5)

AC_A(6) (3958.4, 1543.5)

AC_A(7) (3958.4, 1283.5)

AC_R(2) (3958.4, 1028.5)

AC_R(3) (3958.4, 768.5)

VPP/TEST (3958.4, 508.5)

VSS ( 428.5, 4453.4)

OSCIN ( 593.5, 4453.4)

VSS ( 758.5, 4453.4)

OSCOUT ( 923.5, 4453.4)

RESET (1088.5, 4453.4)

VMULT (1252.9, 4453.4)

VREG (1418.5, 4453.4)

VSS_REG (1588.5, 4453.4)

VSS (1753.5, 4453.4)

VBAT (1923.5, 4453.4)

DAS_AO (3114.6, 4453.4)

DAS_AI_M (3293.5, 4453 .4)

DAS_AI_P (3458.5, 4453.4)

DAS_OUT (3628.5, 4453.4)

( 398.5, 47.6) PB(0)

( 533.5, 47.6) PB(1)

( 668.5, 47.6) PB(2)

( 798.5, 47.6) PB(3)

( 933.5, 47.6) PB(4)

(1063.5, 47.6) VBAT

(1198.5, 47.6) PB(5)

(1328.5, 47.6) PB(6)

(1463.5, 47.6) PB(7)

(1593.5, 47.6) DAB_R_P

(1728.5, 47.6) DAB_R_M

(1858.5, 47.6) DAB_OUT

(2042.4, 47.6) DAB_AO_P

(2683.3, 47.6) DAB_AO_M

(3363.5,47.6) VSS

(3498.5, 47.6) DAB_AI_P

(3628.4, 47.6) DAB_AI_M

4100

4600

Figure 1-2. Die dimensions and pin coordinates (in µm)

1-5

XE8805/05A

1.2.2 LQFP-64

The XE8805/05A is delivered in a LQFP-64 package. The pin map is given below.

PC(7)

PC(6)

PC(5)

PC(4)

PC(3)

PC(2)

PC(1)

PC(0)

PA(7)

PA(6)

PA(5)

PA(4)

PA(3)

PA(2)

PA(1)

PA(0)

VPP/TEST

AC_R(3)

AC_R(2)

AC_A(7)

AC_A(6)

AC_A(5)

AC_A(4)

AC_A(3)

AC_A(2)

AC_A(1)

AC_A(0)

AC_R(1)

AC_A(0)

DAS_OUT

DAS_AI_P

DAS_AI_M

DAS_AO

VBAT

VSS

VSS_REG

VREG

VMULT

RESET

OSCOUT

OSCIN

DAB_AI_M

DAB_AI_P

DAB_AO_M

DAB_AO_P

DAB_OUT

DAB_R_M

DAB_R_P

PB(7)

PB(6)

PB(5)

PB(4)

PB(3)

PB(2)

PB(1)

PB(0)

Figure 1-3. LQFP-64 pin map

Package pin name Package pin name

1 PA(0) 33 VPP/TEST

2 PA(1) 34 NC

3 PA(2) 35 AC_R(3)

4 PA(3) 36 AC_R(2)

5 PA(4) 37 AC_A(7)

6 PA(5) 38 AC_A(6)

7 PA(6) 39 AC_A(5)

8 PA(7) 40 AC_A(4)

9 PC(0) 41 AC_A(3)

10 PC(1) 42 AC_A(2)

11 PC(2) 43 AC_A(1)

12 PC(3) 44 AC_A(0)

13 PC(4) 45 AC_R(1)

14 PC(5) 46 AC_R(0)

15 PC(6) 47 NC

16 PC(7) 48 NC

17 PB(0) 49 NC

18 PB(1) 50 NC

19 PB(2) 51 DAS_OUT

20 PB(3) 52 DAS_AI_P

1-6

XE8805/05A

Package pin name Package pin name

21 PB(4) 53 DAS_AI_M

22 PB(5) 54 DAS_AO

23 PB(6) 55 VBAT

24 PB(7) 56 VSS

25 DAB_R_P 57 VSS_REG

26 DAB_R_M 58 VREG

27 DAB_OUT 59 NC

28 DAB_AO_P 60 VMULT

29 DAB_AO_M 61 RESET

30 DAB_AI_P 62 OSCOUT

31 DAB_AI_M 63 OSCIN

32 NC 64 NC

Table 1-1. Bonding plan of the LQFP-64 package (LQFP 64L 10x10mm thick 1.6 mm)

1.3 Pin assignment

The table below gives a short description of the different pin assignments.

Pin Assignment

VBAT Positive power supply

VSS VSS_REG Negative power supply

VREG Connection for the mandatory external capacitor of the voltage regulator

VPP/TEST High voltage supply for flash memory programming (NC in ROM versions)

RESET Resets the circuit when the voltage is high

OSCIN/OSCOUT Quartz crystal connections, also used for flash memory programming

PA(7:0) Parallel input port A pins

PB(7:0) Parallel I/O port B pins

PC(7:0) Parallel I/O port C pins

AC_A(7:0) Acquisition chain input pins

AC_R(3:0) Acquisition chain reference pins

VMULT Connection for the external capacitor if VBAT is below 3V

DAB_OUT Bias D/A output

DAB_R_x Bias D/A reference (x=P: plus, x=M: minus)

DAB_Ax_y Bias D/A amplifier IO (x=I: input, x=O: output ; y=P: plus, y=M: minus)

DAS_OUT Signal D/A output

DAS_AI_x Signal D/A amplifier inputs (x=P: plus, x=M: minus)

DAS_AO Signal D/A amplifier output

Table 1-2. Pin assignment

Table 1-3 gives a more detailed pin map for the different pins. It also indicates the possible I/O configuration of

these pins. The indications in blue bold are the configuration at start-up.

The pins CNTx pins are possible counter inputs, PWMx are possible PWM outputs.

1-7

XE8805/05A

pin function I/O configuration

lqfp-64

first

second

third

POWER

1 PA(0) CNTA

X X

2 PA(1) CNTB

X X

3 PA(2) CNTC

X X

4 PA(3) CNTD

X X

5 PA(4)

X X

6 PA(5)

X X

7 PA(6)

X X

8 PA(7)

X X

9 PC(0)

10 PC(1)

11 PC(2)

12 PC(3)

13 PC(4)

14 PC(5)

15 PC(6)

16 PC(7)

17 PB(0) PWM0 X X

X X X X

18 PB(1) PWM1 X X

X X X X

19 PB(2) X X

X X X X

20 PB(3) X X

X X X X

21 PB(4) USRT_S0 X X

X X X X

22 PB(5) USRT_S1 X X

X X X X

23 PB(6) UART_Tx X X

X X X X

24 PB(7) UART_Rx X X

X X X X

25 DAB_R_P

26 DAB_R_M

27 DAB_OUT

28 DAB_AO_P

29 DAB_AO_M

30 DAB_AI_P

31 DAB_AI_M

33 VPP TEST

35 AC_R(3)

36 AC_R(2)

37 AC_A(7)

38 AC_A(6)

39 AC_A(5)

40 AC_A(4)

41 AC_A(3)

42 AC_A(2)

43 AC_A(1)

44 AC_A(0)

45 AC_R(1)

46 AC_R(0)

51 DAS_OUT

52 DAS_AI_P

53 DAS_AI_M

54 DAS_AO

55 VBAT

1-8

XE8805/05A

pin function I/O configuration

lqfp-64

first

second

third

POWER

56 VSS

57 VSS_REG

58 VREG

60 VMULT

61 RESET

62 OSCOUT

63 OSCIN

Pin map table legend:

blue bold: configuration at start up

AI: analog input

AO: analog output

DI: digital input

DO: digital output

OD: nMOS open drain output

PU: pull-up resistor

POWER: power supply

Table 1-3. Pin description table

2-1

XE8805/05A

2 XE8805/05A Performance

2.1 Absolute maximum ratings 2-2

2.2 Operating range 2-2

2.3 Supply configurations 2-3

2.3.1 Flash circuit 2-3

2.3.2 ROM circuit 2-3

2.4 Current consumption 2-5

2.5 Operating speed 2-6

2.5.1 Flash version 2-6

2.5.2 ROM circuit version 2-6

2-2

XE8805/05A

2.1 Absolute maximum ratings

Table 2-1. Absolute maximum ratings

Min. Max. Note

Voltage applied to VBAT with respect to VSS -0.3 6.0 V

Voltage applied to VPP with respect to VSS VBAT-0.3 12 V

Voltage applied to all pins except VPP and VBAT VSS-0.3 VBAT+0.3 V

Storage temperature (ROM device or unprogrammed

flash device) -55 150 °C

Storage temperature (programmed flash device) -40 85 °C

Stresses beyond the absolute maximal ratings may cause permanent damage to the device. Functional operation

at the absolute maximal ratings is not implied. Exposure to conditions beyond the absolute maximal ratings may

affect the reliability of the device.

2.2 Operating range

Table 2-2. Operating range for the flash device

Min. Max. Note

Voltage applied to VBAT with respect to VSS 2.4 5.5 V

Voltage applied to VBAT with respect to VSS during

the flash programming 3.3 5.5 V 1

Voltage applied to VPP with respect to VSS VBAT 11.5 V

Voltage applied to all pins except VPP and VBAT VSS VBAT V

Operating temperature range -40 85 °C

Capacitor on VREG (flash version) 0.8 1.2 µF 2

Capacitor on VMULT 1.0 3.0 nF 3

1. During the programming of the device, the supply voltage should at least be equal to the supply voltage

used during normal operation.

2. The capacitor on VREG is mandatory.

3. The capacitor on VMULT is optional. The capacitor has to be present if the multiplier is enabled. The

multiplier has to be enabled if VBAT<3.0V.

Table 2-3. Operating range for the ROM device

Min. Max. Note

Voltage applied to VBAT with respect to VSS 2.4 5.5 V

Voltage applied to all pins except VPP and VBAT VSS VBAT V

Operating temperature range -40 125 °C

Capacitor on VREG 0.1 1.2 µF 1

Capacitor on VMULT 1.0 3.0 nF 2

1. The capacitor may be omitted when VREG is connected to VBAT.

2. The capacitor on VMULT is optional. The capacitor has to be present if the multiplier is enabled. The

multiplier has to be enabled if VBAT<3.0V.

All specifications in this document are valid for the complete operating range unless otherwise specified.

2-3

XE8805/05A

Table 2-4. Operating range of the Flash memory

Min. Max. Note

Retention time at 85°C 10 years 1

Retention time at 55°C 100 years 1

Number of programming cycles 10 2

1. Valid only if programmed using a programming tool that is qualified

2. Circuits can be programmed more than 10 times but after that, the retention time is no longer guaranteed.

All qualification tests have been done after 10 cycles.

2.3 Supply configurations

2.3.1 Flash circuit

The flash version of the circuit can be run from a supply between 2.4V and 5.5V (Figure 2-1). The capacitor on

VREG has to be connected at all times (value in Table 2-2) to guarantee proper operation of the device. The

capacitor on VMULT is only required if the circuit is to be operated below 3V.

VBAT

VREG

VMULT

VSS

2.4V – 5.5V

Cvreg

Cvmult

Figure 2-1. Supply configuration for the flash circuit.

2.3.2 ROM circuit

For the ROM version, two possible operating modes exist: with and without voltage regulator. Using the voltage

regulator, low power consumption will be obtained even with supply voltages above 2.4V. Without the voltage

regulator (i.e. VREG short-circuited to VBAT), a higher speed can be obtained.

2.3.2.1 Low power operation

In this case, the internal voltage regulator is used in order to maintain low power consumption independent from

the supply voltage. The capacitor on VREG has to be connected at all times (value in Table 2-3) to guarantee

proper operation of the device. The capacitor on VMULT has to be connected only when VBAT<3V.

2-4

XE8805/05A

VBAT

VREG

VMULT

VSS

2.4V – 5.5V

Cvreg

Cvmult

Figure 2-2. Supply voltage connections for low power operation of the ROM version.

2.3.2.2 High speed operation

In this case, the internal voltage regulator is not used. The operation speed of the circuit can be increased with

increasing supply voltage but the supply current will also increase. The capacitor on VMULT has to be connected

only when VBAT<3V. In this case, the supply voltage can decrease down to 2.15V. Beware however that the

zoomingADCTM will not run below 2.4V (see Figure 2-4). In this configuration, the circuit can not be used above

3.3V.

VBAT

VREG

VMULT

VSS

2.15V – 3.3V

Cvmult

Figure 2-3. Supply voltage connections for high speed operation of the ROM version.

2-5

XE8805/05A

0 2.15 2.4 3.3 VBAT (V)

CPU

parallel and serial ports

RC and crystal oscillator

VLD

Counters and PWM

DAS (without amplifier)

acquisition chain

voltage multiplier

DAB

Figure 2-4. Operation range of the different circuit blocks

2.4 Current consumption

The tables below give the current consumption for the circuit in different configurations. The figures are indicative

only and may change as a function of the actual software implemented in the circuit.

Table 2-5 gives the current consumption for the flash version of the circuit. The peripherals are disabled. The

parallel ports A and B are configured in input with pull up, the parallel port C is configured as an output. Their pins

are not connected externally. The pin RESET is connected to VSS and the pin VPP/TEST is connected to VBAT.

The inputs of the acquisition chain are connected to VSS.

Table 2-5. Typical current consumption of the XE8805 version (8k instructions flash memory)

Operation mode CPU RC Xtal Consumption comments Note

High speed CPU 1 MIPS 1 MHz Off 310 µA 2.4V<>5.5V, 27°C

Low power CPU 32 kIPS Off 32 kHz 10 µA 2.4V <>5.5V, 27°C

Low power time

keeping HALT Off 32 kHz 1.0 µA 2.4V <>5.5V, 27°C

Fast wake-up

time keeping HALT Ready 32kHz 1.7 µA 2.4V <>5.5V, 27°C

Immediate wake-

up time keeping HALT 100 kHz Off 1.4 µA 2.4V <>5.5V, 27°C

VLD static current 15 µA 2.4V <>5.5V, 27°C

16 bit resolution

data acquisition HALT 2 MHz Off 190 µA 3.0V, 27°C 1

12 bit , gain 100,

data acquisition HALT 2 MHz Off 460 µA 3.0V, 27°C 2

1. PGA disabled, ADC enabled, 16 bit resolution

2. PGA 1 disabled, PGA 2 and 3 enabled, ADC enabled, 12 bit resolution

For more information concerning the current consumption of the zoomingADCTM, see the chapter power

consumption in the acquisition chain documentation which shows the current consumption of this block as a

function of temperature and voltage and for different configurations of the PGA and ADC.

The power consumption of the ROM version of the circuit is identical if it is configured as shown in Figure 2-2. In

the high speed configuration, the current consumption will increase proportional with VBAT.

2-6

XE8805/05A

2.5 Operating speed

2.5.1 Flash version

The speed of the devices is not highly dependent upon the supply voltage. However, by limiting the temperature

range, the speed can be increased. The minimal guaranteed speed as a function of the supply voltage and

maximal temperature operating temperature is given in Figure 2-5.

22.533.544.555.5

supply voltage VBAT (V)

speed (MIPS)

85°C 45°C

Figure 2-5. Guaranteed speed as a function of the supply voltage and maximal temperature.

2.5.2 ROM circuit version

2.5.2.1 Low power supply configuration

In the low power supply configuration as shown in Figure 2-2, the operating speed does not depend highly on the

supply voltage as shown in Figure 2-6.

0.5

1.5

2.5

3.5

22.533.544.555.5

supply voltage VBA T (V )

speed (MIPS)

85°C 45°C 125°C

Figure 2-6. Guaranteed speed as a function of supply voltage and for different maximal temperatures using the

voltage regulator.

2.5.2.2 High speed supply configuration

In the high speed supply configuration of Figure 2-3, the guaranteed speed of the circuit is shown in Figure 2-7.

2-7

XE8805/05A

2 2.2 2.4 2.6 2.8 3 3.2 3.4

supply voltage VBAT (V)

speed (MIPS)

85°C 45°C 125°C

Figure 2-7. Guaranteed speed as a function of supply voltage and for three temperature ranges when

VREG=VBAT.

3-1

XE8805/05A

3. CPU

CONTENTS

3.1 CPU description 3-2

3.2 CPU internal registers 3-2

3.3 CPU instruction short reference 3-4

3-2

XE8805/05A

3.1 CPU description

The CPU of the XE8000 series is a low power RISC core. It has 16 internal registers for efficient implementation of

the C compiler. Its instruction set is made up of 35 generic instructions, all coded on 22 bits, with 8 addressing

modes. All instructions are executed in one clock cycle, including conditional jumps and 8x8 multiplication. The

circuit therefore runs on 1 MIPS on a 1MHz clock.

The CPU hardware and software description is given in the document “Coolrisc816 Hardware and Software

Reference Manual”. A short summary is given in the following paragraphs.

The good code efficiency of the CPU core makes it possible to compute a polynomial like

YBBXYAAZ ⋅++⋅⋅+= 1010 )( in less than 300 clock cycles (software code generated by the XEMICS C-

compiler, all numbers are signed integers on 16 bits).

3.2 CPU internal registers

As shown in Figure 3-1, the CPU has 16 internal 8-bit registers. Some of these registers can be concatenated to a

16-bit word for use in some instructions. The function of these registers is defined in Table 3-1. The status register

stat (Table 3-2) is used to manage the different interrupt and event levels. An interrupt or an event can both be

used to wake up after a HALT instruction. The difference is that an interrupt jumps to a special interrupt function

whereas an event continues the software execution with the instruction following the HALT instruction.

The program counter (PC) is a 16 bit register that indicates the address of the instruction that has to be executed.

The stack (STn) is used to memorise the return address when executing subroutines or interrupt routines.

Instruction

memory

22bit

CPU

CPU internal registers

stat

iph ipl

i3h i3l

i2h i2l

i1h i1l

i0h i0l

Data memory

data bus

instruction bus

ST1

ST2

ST3

ST4

program counter stack

Figure 3-1. CPU internal registers

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XE8805/05A

r0 general purpose

r1 general purpose

r2 general purpose

r3 data memory offset

i0h MSB of the data memory index i0

i0l LBS of the data memory index i0

i1h MSB of the data memory index i1

i1l LBS of the data memory index i1

i2h MSB of the data memory index i2

i2l LBS of the data memory index i2

i3h MSB of the data memory index i3

i3l LBS of the data memory index i3

iph MSB of the program memory index ip

ipl LBS of the program memory index ip

stat status register

a accumulator

Table 3-1. CPU internal register definition

bit name function

7 IE2 enables (when 1) the interrupt request of level 2

6 IE1 enables (when 1) the interrupt request of level 1

5 GIE enables (when 1) all interrupt request levels

4 IN2 interrupt request of level 2. The interrupts labelled “low” in the interrupt handler are

routed to this interrupt level. This bit has to be cleared when the interrupt is served.

3 IN1 interrupt request of level 1. The interrupts labelled “mid” in the interrupt handler are

routed to this interrupt level. This bit has to be cleared when the interrupt is served.

2 IN0 interrupt request of level 0. The interrupts labelled “hig” in the interrupt handler are

routed to this interrupt level. This bit has to be cleared when the interrupt is served.

1 EV1 event request of level 1. The events labelled “low” in the event handler are routed to

this event level. This bit has to be cleared when the event is served.

0 EV0 event request of level 1. The events labelled “hig” in the event handler are routed to

this event level. This bit has to be cleared when the event is served.

Table 3-2. Status register description

The CPU also has a number of flags that can be used for conditional jumps. These flags are defined in Table 3-3.

symbol name function

Z zero Z=1 when the accumulator a content is zero

C carry This flag is used in shift or arithmetic operations.

For a shift operation, it has the value of the bit that was shifted out (LSB for shift

right, MSB for shift left).

For an arithmetic operation with unsigned numbers:

it is 1 at occurrence of an overflow during an addition (or equivalent).

it is 0 at occurrence of an underflow during a subtraction (or equivalent).

V overflow This flag is used in shift or arithmetic operations.

For arithmetic or shift operations with signed numbers, it is 1 if an overflow or

underflow occurs.

Table 3-3. Flag description

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XE8805/05A

3.3 CPU instruction short reference

Table 3-4 shows a short description of the different instructions available on the Coolrisc816. The notation cc in the

conditional jump instruction refers to the condition description as given in Table 3-6. The notation reg, reg1, reg2,

reg3 refers to one of the CPU internal registers of Table 3-1. The notation eaddr and DM(eaddr) refer to one of the

extended address modes as defined in Table 3-5. The notation DM(xxx) refers to the data memory location with

address xxx.

Instruction Modification Operation

Jump addr[15:0] -,-,-, - PC := addr[15:0]

Jump ip -,-,-, - PC := ip

Jcc addr[15:0] -,-,-, - if cc is true then PC := addr[15:0]

Jcc ip -,-,-, - if cc is true then PC := ip

Call addr[15:0] -,-,-, - STn+1 := STn (n>1); ST1 := PC+1; PC := addr[15:0]

Call ip -,-,-, - STn+1 := STn (n>1); ST1 := PC+1; PC := ip

Calls addr[15:0] -,-,-, - ip := PC+1; PC := addr[15:0]

Calls ip -,-,-, - ip := PC+1; PC := ip

Ret -,-,-, - PC := ST1; STn := STn+1 (n>1)

Rets -,-,-, - PC := ip

Reti -,-,-, - PC := ST1; STn := STn+1 (n>1); GIE :=1

Push -,-,-, - PC := PC+1; STn+1 := STn (n>1); ST1 := ip

Pop -,-,-, - PC := PC+1; ip := ST1; STn := STn+1 (n>1)

Move reg,#data[7:0] -,-, Z, a a := data[7:0]; reg := data[7:0]

Move reg1, reg2 -,-, Z, a a := reg2; reg1 := reg2

Move reg, eaddr -,-, Z, a a := DM(eaddr); reg := DM(eaddr)

Move eaddr, reg -,-,-, - DM(eaddr) := reg

Move addr[7:0],#data[7:0] -,-,-, - DM(addr[7:0]) := data[7:0]

Cmvd reg1, reg2 -,-, Z, a a := reg2; if C=0 then reg1 := a;

Cmvd reg, eaddr -,-, Z, a a := DM(eaddr); if C=0 then reg := a

Cmvs reg1, reg2 -,-, Z, a a := reg2; if C=1 then reg1 := a;

Cmvs reg, eaddr -,-, Z, a a := DM(eaddr); if C=1 then reg := a

Shl reg1, reg2 C, V, Z, a a := reg2<<1; a[0] := 0; C := reg2[7]; reg1 := a

Shl reg C, V, Z, a a := reg<<1; a[0] := 0; C := reg[7]; reg := a

Shl reg, eaddr C, V, Z, a a := DM(eaddr)<<1; a[0] :=0; C := DM(eaddr)[7]; reg := a

Shlc reg1, reg2 C, V, Z, a a := reg2<<1; a[0] := C; C := reg2[7]; reg1 := a

Shlc reg C, V, Z, a a := reg<<1; a[0] := C; C := reg[7]; reg := a

Shlc reg, eaddr C, V, Z, a a := DM(eaddr)<<1; a[0] := C; C := DM(eaddr)[7]; reg := a

Shr reg1, reg2 C, V, Z, a a := reg2>>1; a[7] := 0; C := reg2[0]; reg1 :=a

Shr reg C, V, Z, a a := reg>>1; a[7] := 0; C := reg[0]; reg := a

Shr reg, eaddr C, V, Z, a a := DM(eaddr)>>1; a[7] := 0; C := DM(eaddr)[0]; reg := a

Shrc reg1, reg2 C, V, Z, a a := reg2>>1; a[7] := C; C := reg2[0]; reg1 := a

Shrc reg C, V, Z, a a := reg>>1; a[7] := C; C := reg[0]; reg := a

Shrc reg, eaddr C, V, Z, a a := DM(eaddr)>>1; a[7] := C; C := DM(eaddr)[0]; reg := a

Shra reg1, reg2 C, V, Z, a a := reg2>>1; a[7] := reg2[7]; C := reg2[0]; reg1 := a

Shra reg C, V, Z, a a := reg>>1; a[7] := reg[7]; C := reg[0]; reg := a

Shra reg, eaddr C, V, Z, a a := DM(eaddr)>>1; a[7] := DM(eaddr)[7]; C := DM(eaddr)[0]; reg := a

Cpl1 reg1, reg2 -,-, Z, a a := NOT(reg2); reg1 := a

Cpl1 reg -,-, Z, a a := NOT(reg); reg := a

Cpl1 reg, eaddr -,-, Z, a a := NOT(DM(eaddr)); reg := a

Cpl2 reg1, reg2 C, V, Z, a a := NOT(reg2)+1; if a=0 then C:=1 else C := 0; reg1 := a

Cpl2 reg C, V, Z, a a := NOT(reg)+1; if a=0 then C:=1 else C := 0; reg := a

Cpl2 reg, eaddr C, V, Z, a a := NOT(DM(eaddr))+1; if a=0 then C:=1 else C := 0; reg := a

Cpl2c reg1, reg2 C, V, Z, a a := NOT(reg2)+C; if a=0 and C=1 then C:=1 else C := 0; reg1 := a

Cpl2c reg C, V, Z, a a := NOT(reg)+C; if a=0 and C=1 then C:=1 else C := 0; reg := a

Cpl2c reg, eaddr C, V, Z, a a := NOT(DM(eaddr))+C; if a=0 and C=1 then C:=1 else C := 0; reg := a

Inc reg1, reg2 C, V, Z, a a := reg2+1; if a=0 then C := 1 else C := 0; reg1 := a

Inc reg C, V, Z, a a := reg+1; if a=0 then C := 1 else C := 0; reg := a

Inc reg, eaddr C, V, Z, a a := DM(eaadr)+1; if a=0 then C := 1 else C := 0; reg := a

Incc reg1, reg2 C, V, Z, a a := reg2+C; if a=0 and C=1 then C := 1 else C := 0; reg1 := a

Incc reg C, V, Z, a a := reg+C; if a=0 and C=1 then C := 1 else C := 0; reg := a

Incc reg, eaddr C, V, Z, a a := DM(eaadr)+C; if a=0 and C=1 then C := 1 else C := 0; reg := a

Dec reg1, reg2 C, V, Z, a a := reg2-1; if a=hFF then C := 0 else C := 1; reg1 := a

3-5

XE8805/05A

Dec reg C, V, Z, a a := reg-1; if a=hFF then C := 0 else C := 1; reg := a

Dec reg, eaddr C, V, Z, a a := DM(eaddr)-1; if a=hFF then C := 0 else C := 1; reg := a

Decc reg1, reg2 C, V, Z, a a := reg2-(1-C); if a=hFF and C=0 then C := 0 else C := 1; reg1 := a

Decc reg C, V, Z, a a := reg-(1-C); if a=hFF and C=0 then C := 0 else C := 1; reg := a

Decc reg, eaddr C, V, Z, a a := DM(eaddr)-(1-C); if a=hFF and C=0 then C := 0 else C := 1; reg := a

And reg,#data[7:0] -,-, Z, a a := reg and data[7:0]; reg := a

And reg1, reg2, reg3 -,-, Z, a a := reg2 and reg3; reg1 := a

And reg1, reg2 -,-, Z, a a := reg1 and reg2; reg1 := a

And reg, eaddr -,-, Z, a a := reg and DM(eaddr); reg := a

Or reg,#data[7:0] -,-, Z, a a := reg or data[7:0]; reg := a

Or reg1, reg2, reg3 -,-, Z, a a := reg2 or reg3; reg1 := a

Or reg1, reg2 -,-, Z, a a := reg1 or reg2; reg1 := a

Or reg, eaddr -,-, Z, a a := reg or DM(eaddr); reg := a

Xor reg,#data[7:0] -,-, Z, a a := reg xor data[7:0]; reg := a

Xor reg1, reg2, reg3 -,-, Z, a a := reg2 xor reg3; reg1 := a

Xor reg1, reg2 -,-, Z, a a := reg1 xor reg2; reg1 := a

Xor reg, eaddr -,-, Z, a a := reg or DM(eaddr); reg := a

Add reg,#data[7:0] C, V, Z, a a := reg+data[7:0]; if overflow then C:=1 else C := 0; reg := a

Add reg1, reg2, reg3 C, V, Z, a a := reg2+reg3; if overflow then C:=1 else C := 0; reg1 := a

Add reg1, reg2 C, V, Z, a a := reg1+reg2; if overflow then C:=1 else C := 0; reg1 := a

Add reg, eaddr C, V, Z, a a := reg+DM(eaddr); if overflow then C:=1 else C := 0; reg := a

Addc reg,#data[7:0] C, V, Z, a a := reg+data[7:0]+C; if overflow then C:=1 else C := 0; reg := a

Addc reg1, reg2, reg3 C, V, Z, a a := reg2+reg3+C; if overflow then C:=1 else C := 0; reg1 := a

Addc reg1, reg2 C, V, Z, a a := reg1+reg2+C; if overflow then C:=1 else C := 0; reg1 := a

Addc reg, eaddr C, V, Z, a a := reg+DM(eaddr)+C; if overflow then C:=1 else C := 0; reg := a

Subd reg,#data[7:0] C, V, Z, a a := data[7:0]-reg; if underflow then C := 0 else C := 1; reg := a

Subd reg1, reg2, reg3 C, V, Z, a a := reg2-reg3; if underflow then C := 0 else C := 1; reg1 := a

Subd reg1, reg2 C, V, Z, a a := reg2-reg1; if underflow then C := 0 else C := 1; reg1 := a

Subd reg, eaddr C, V, Z, a a := DM(eaddr)-reg; if underflow then C := 0 else C := 1; reg := a

Subdc reg,#data[7:0] C, V, Z, a a := data[7:0]-reg-(1-C); if underflow then C := 0 else C := 1; reg := a

Subdc reg1, reg2, reg3 C, V, Z, a a := reg2-reg3-(1-C); if underflow then C := 0 else C := 1; reg1 := a

Subdc reg1, reg2 C, V, Z, a a := reg2-reg1-(1-C); if underflow then C := 0 else C := 1; reg1 := a

Subdc reg, eaddr C, V, Z, a a := DM(eaddr)-reg-(1-C); if underflow then C := 0 else C := 1; reg := a

Subs reg,#data[7:0] C, V, Z, a a := reg-data[7:0]; if underflow then C := 0 else C := 1; reg := a

Subs reg1, reg2, reg3 C, V, Z, a a := reg3-reg2; if underflow then C := 0 else C := 1; reg1 := a

Subs reg1, reg2 C, V, Z, a a := reg1-reg2; if underflow then C := 0 else C := 1; reg1 := a

Subs reg, eaddr C, V, Z, a a := reg-DM(eaddr); if underflow then C := 0 else C := 1; reg := a

Subsc reg,#data[7:0] C, V, Z, a a := reg-data[7:0]-(1-C); if underflow then C := 0 else C := 1; reg := a

Subsc reg1, reg2, reg3 C, V, Z, a a := reg3-reg2-(1-C); if underflow then C := 0 else C := 1; reg1 := a

Subsc reg1, reg2 C, V, Z, a a := reg1-reg2-(1-C); if underflow then C := 0 else C := 1; reg1 := a

Subsc reg, eaddr C, V, Z, a a := reg-DM(eaddr)-(1-C); if underflow then C := 0 else C := 1; reg := a

Mul reg,#data[7:0] u, u, u, a a := (data[7:0]*reg)[7:0]; reg := (data[7:0]*reg)[15:8]

Mul reg1, reg2, reg3 u, u, u, a a := (reg2*reg3)[7:0]; reg1 := (reg2*reg3)[15:8]

Mul reg1, reg2 u, u, u, a a := (reg2*reg1)[7:0]; reg1 := (reg2*reg1)[15:8]

Mul reg, eaddr u, u, u, a a := (DM(eaddr)*reg)[7:0]; reg := (DM(eaddr)*reg)[15:8]

Mula reg,#data[7:0] u, u, u, a a := (data[7:0]*reg)[7:0]; reg := (data[7:0]*reg)[15:8]

Mula reg1, reg2, reg3 u, u, u, a a := (reg2*reg3)[7:0]; reg1 := (reg2*reg3)[15:8]

Mula reg1, reg2 u, u, u, a a := (reg2*reg1)[7:0]; reg1 := (reg2*reg1)[15:8]

Mula reg, eaddr u, u, u, a a := (DM(eaddr)*reg)[7:0]; reg := (DM(eaddr)*reg)[15:8]

Mshl reg,#shift[2:0] u, u, u, a a := (reg*2shift)[7:0]; reg := (reg*2shift)[15:8]

Mshr reg,#shift[2:0] u, u, u, a a := (reg*2(8-shift)[7:0]; reg := (reg*2(8-shift)[15:8]

Mshra reg,#shift[2:0] u, u, u, a* a := (reg*2(8-shift)[7:0]; reg := (reg*2(8-shift)[15:8]

Cmp reg,#data[7:0] C, V, Z, a a := data[7:0]-reg; if underflow then C :=0 else C:=1; V := C and (not Z)

Cmp reg1, reg2 C, V, Z, a a := reg2-reg1; if underflow then C :=0 else C:=1; V := C and (not Z)

Cmp reg, eaddr C, V, Z, a a := DM(eaddr)-reg; if underflow then C :=0 else C:=1; V := C and (not Z)

Cmpa reg,#data[7:0] C, V, Z, a a := data[7:0]-reg; if underflow then C :=0 else C:=1; V := C and (not Z)

Cmpa reg1, reg2 C, V, Z, a a := reg2-reg1; if underflow then C :=0 else C:=1; V := C and (not Z)

Cmpa reg, eaddr C, V, Z, a a := DM(eaddr)-reg; if underflow then C :=0 else C:=1; V := C and (not Z)

Tstb reg,#bit[2:0] -, -, Z, a a[bit] := reg[bit]; other bits in a are 0

Setb reg,#bit[2:0] -, -, Z, a reg[bit] := 1; other bits unchanged; a := reg

Clrb reg,#bit[2:0] -, -, Z, a reg[bit] := 0; other bits unchanged; a := reg

Invb reg,#bit[2:0] -, -, Z, a reg[bit] := not reg[bit]; other bits unchanged; a := reg

3-6

XE8805/05A

Sflag -,-,-, a a[7] := C; a[6] := C xor V; a[5] := ST full; a[4] := ST empty

Rflag reg C, V, Z, a a := reg << 1; ; a[0] := 0; C := reg[7]

Rflag eaddr C, V, Z, a a := DM(eaddr)<<1; a[0] :=0; C := DM(eaddr)[7]

Freq divn -,-,-, - reduces the CPU frequency (divn=nodiv, div2, div4, div8, div16)

Halt -,-,-, - halts the CPU

Nop -,-,-, - no operation

- = unchanged, u = undefined, *MSHR reg,# 1 doesn’t shift by 1

Table 3-4. Instruction short reference

The Coolrisc816 has 8 different addressing modes. These modes are described in Table 3-5. In this table, the

notation ix refers to one of the data memory index registers i0, i1, i2 or i3. Using eaddr in an instruction of Table 3-4

will access the data memory at the address DM(eaddr) and will simultaneously execute the index operation.

extended address

eaddr accessed data memory

location

DM(eaddr)

index

operation

addr[7:0] DM(h00&addr[7:0]) - direct addressing

(ix) DM(ix) - indexed addressing

(ix, offset[7:0]) DM(ix+offset) - indexed addressing with immediate offset

(ix,r3) DM(ix+r3) - indexed addressing with register offset

(ix)+ DM(ix) ix := ix+1 indexed addressing with index post-increment

(ix,offset[7:0])+ DM(ix+offset) ix := ix+offset indexed addressing with index post-increment by the offset

-(ix) DM(ix-1) ix := ix-1 indexed addressing with index pre-decrement

-(ix,offset[7:0]) DM(ix-offset) ix := ix -offset indexed addressing with index pre-decrement by the offset

Table 3-5. Extended address mode description

Eleven different jump conditions are implemented as shown in Table 3-6. The contents of the column CC in this

table should replace the CC notation in the instruction description of Table 3-4.

CC condition

CS C=1

CC C=0

ZS Z=1

ZC Z=0

VS V=1

VC V=0

EV (EV1 or EV0)=1

After CMP op1,op2

EQ op1=op2

NE op1≠op2

GT op1>op2

GE op1≥op2

LT op1<op2

LE op1≤op2

Table 3-6. Jump condition description

4-1

XE8805/05A

4 Memory mapping

4.1 Memory organisation 4-2

4.2 Quick reference data memory register map 4-2

4.2.1 Low power data registers (h0000-h0007) 4-3

4.2.2 System, clock configuration and reset configuration (h0010-h001F) 4-4

4.2.3 Port A (h0020-h0027) 4-4

4.2.4 Port B (h0028-h002F) 4-4

4.2.5 Port C (h0030-h0033) 4-5

4.2.6 Flash programming (h0038-003B) 4-5

4.2.7 Event handler (h003C-h003F) 4-5

4.2.8 Interrupt handler (h0040-h0047) 4-6

4.2.9 USRT (h0048-h004F) 4-7

4.2.10 UART (h0050-h0057) 4-7

4.2.11 Counter/Timer/PWM registers (h0058-h005F) 4-7

4.2.12 Acquisition chain registers (h0060-h0067) 4-8

4.2.13 Signal D/A registers (h0074-h0077) 4-8

4.2.14 Bias D/A registers (h0078-h0079) 4-8

4.2.15 Voltage multiplier (h007C) 4-8

4.2.16 Voltage Level Detector registers (h007E-h007F) 4-9

4.2.17 RAM (h0080-h027F) 4-9

4-2

XE8805/05A

4.1 Memory organisation

The XE8805 CPU is built with a Harvard architecture. The Harvard architecture uses separate instruction and data

memories. The instruction bus and data bus are also separated. The advantage of such a structure is that the CPU

can get a new instruction and read/write data simultaneously. The circuit configuration is shown in Figure 4-1. The

CPU has its 16 internal registers. The instruction memory has a capacity of 8192 22-bit instructions. The data

memory space has 8 low power registers, the peripheral register space and 512 bytes of RAM.

Figure 4-1. Memory mapping

The CPU internal registers are described in the CPU chapter. A short reference of the low power registers and

peripheral registers is given in 4.2.

4.2 Quick reference data memory register map

The data register map is given in the tables below. A more detailed description of the different registers is given in

the detailed description of the different peripherals.

The tables give the following information:

1. The register name and register address

2. The different bits in the register

3. The access mode of the different bits (see Table 4-1 for code description)

4. The reset source and reset value of the different bits

The reset source coding is given in Table 4-2. To get a full description of the reset sources, please refer to the

reset block chapter.

µF µF 0h027F

RAM

capacity:

512 bytes

0h0080

0h1FFF

Instruction

memory

capacity:

8k x 22bit

0h0000

CPU

CPU internal registers

stat

iph ipl

i3h i3l

i2h i2l

i1h i1l

i0h i0l

Low power

RAM

0h0000

0h007F

Peripheral

registers

0h0008

Data memory

data bus

instruction bus

4-3

XE8805/05A

code access mode

r bit can be read

w bit can be written

r0 bit always reads 0

r1 bit always reads 1

c bit is cleared by writing any value

c1 bit is cleared by writing a 1

ca bit is cleared after reading

s special function, verify the detailed description in the respective peripherals

Table 4-1. Access mode codes used in the register definitions

code reset source

sys resetsystem

cold resetcold

pconf resetpconf

sleep resetsleep

Table 4-2. Reset source coding used in the register definitions

4.2.1 Low power data registers (h0000-h0007)

Name

Address

Reg00

h0000 Reg00[7:0]

rw, xxxxxxxx,-

Reg01

h0001 Reg01[7:0]

rw,xxxxxxxx,-

Reg02

h0002 Reg02[7:0]

rw,xxxxxxxx,-

Reg03

h0003 Reg03[7:0]

rw,xxxxxxxx,-

Reg04

h0004 Reg04[7:0]

rw,xxxxxxxx,-

Reg05

h0005 Reg05[7:0]

rw,xxxxxxxx,-

Reg06

h0006 Reg06[7:0]

rw,xxxxxxxx,-

Reg07

h0007 Reg07[/:0]

rw,xxxxxxxx,-

Table 4-3. Low power data registers

4-4

XE8805/05A

4.2.2 System, clock configuration and reset configuration (h0010-h001F)

Name

Address

RegSysCtrl

h0010 SleepEn

rw,0,cold EnResPConf

rw,0,cold EnBusError

rw,0,cold EnResWD

rw,0,cold

RegSysReset

h0011 Sleep

rw,0,sys ResetBusError

rc, 0, cold ResetWD

rc, 0, cold ResetfromportA

rc, 0, cold ResPad

rc,0,cold ResPadSleep

rc,0,cold

RegSysClock

h0012 CpuSel

rw,0,sleep ExtClk

r,0,cold EnExtClock

rw,0,cold BiasRC

rw,1,cold ColdXtal

r,1,sleep ColdRC

r,1,sleep EnableXtal

rw,0,sleep EnableRC

rw,1,sleep

RegSysMisc

h0013

r0 RCOnPA0

rw,0,sleep DebFast

rw,0,sleep OutputCkXtal

rw,0,sleep OutputCpuCk

rw,0,sleep

RegSysWd

h0014

r0 WatchDog[3:0]

s,0000,cold

RegSysPre0

h0015

r0 ResPre

c1r0,0,-

RegSysRcTrim1

h001B

r0 Reserved

rw,0,cold RcFreqRange

rw,0,cold RcFreqCoarse[3:0]

rw,0000,cold

RegSysRcTrim2

h001C

r0 RcFreqFine[5:0]

rw,10000,cold

Table 4-4. Reset block and clock block registers

4.2.3 Port A (h0020-h0027)

Name

Address

RegPAIn

h0020 PAIn[7:0]

RegPADebounce

h0021 PADebounce[7:0]

rw,00000000,pconf

RegPAEdge

h0022 PAEdge[7:0]

rw,00000000,sys

RegPAPullup

h0023 PAPullup[7:0]

rw,00000000,pconf

RegPARes0

h0024 PARes0[7:0]

rw, 00000000, sys

RegPARes1

h0025 PARes1[7:0]

rw,00000000,sys

Table 4-5. Port A registers

4.2.4 Port B (h0028-h002F)

Name

Address

RegPBOut

h0028 PBOut[7:0]

rw,00000000,pconf

RegPBIn

h0029 PBIn[7:0]

RegPBDir

h002A PBDir[7:0]

rw,00000000,pconf

RegPBOpen

h002B PBOpen[7:0]

rw,00000000,pconf

RegPBPullup

h002C PBPullup[7:0]

rw,00000000,pconf

RegPBAna

h002D

r0 PBAna[3:0]

rw,0000,pconf

Table 4-6. Port B registers

4-5

XE8805/05A

4.2.5 Port C (h0030-h0033)

Name

Address

RegPCOut

h0030 PCOut[7:0]

rw,00000000,pconf

RegPCIn

h0031 PCIn[7:0]

r,-,-

RegPCDir

h0032 PD1Dir[7:0]

rw,00000000,pconf

Table 4-7. Port C registers

4.2.6 Flash programming (h0038-003B)

These four registers are used during flash programming only. Refer to the flash programming algorithm

documentation for more details.

4.2.7 Event handler (h003C-h003F)

Name

Address

RegEvn

h003C CntIrqA

rc1,0,sys CntIrqC

rc1,0,sys 128Hz

rc1,0,sys PAEvn[1]

rc1,0,sys CntIrqB

rc1,0,sys CntIrqD

rc1,0,sys 1Hz

rc1,0,sys PAEvn[0]

rc1,0,sys

RegEvnEn

h003D EvnEn[7:0]

rw,00000000,sys

RegEvnPriority

h003E EvnPriority[7:0]

r,11111111,sys

RegEvnEvn

h003F

r0 EvnHigh

r,0,sys EvnLow

r,0,sys

Table 4-8. Event handler registers

The origin of the different events is summarised in the table below.

Event Event source

CntIrqA Counter/Timer A (counter block)

CntIrqB Counter/Timer B (counter block)

CntIrqC Counter/Timer C (counter block)

CntIrqD Counter/Timer D (counter block)

128Hz Low prescaler (clock block)

1Hz Low prescaler (clock block)

PAEvn[1:0] Port A

Table 4-9. Event source description

4-6

XE8805/05A

4.2.8 Interrupt handler (h0040-h0047)

Name

Address

RegIrqHig

h0040 IrqAC

rc1,0,sys 128Hz

rc1,0,sys

r0 CntIrqA

rc1,0,sys CntIrqC

rc1,0,sys

r0 UartIrqTx

rc1,0,sys UartIrqRx

rc1,0,sys

RegIrqMid

h0041 UsrtCond1

rc1,0,sys UrstCond2

rc1,0,sys PAIrq[5]

rc1,0,sys PAIrq[4]

rc1,0,sys 1Hz

rc1,0,sys VldIrq

rc1,0,sys PAIrq[1]

rc1,0,sys PAIrq[0]

rc1,0,sys

RegIrqLow

h0042 PAIrq[7]

rc1,0,sys PAIrq[6]

rc1,0,sys CntIrqB

rc1,0,sys CntIrqD

rc1,0,sys PAIrq[3]

rc1,0,sys PAIrq[2]

rc1,0,sys

RegIrqEnHig

h0043 IrqEnHig[7:0]

rw,0000000,sys

RegIrqEnMid

h0044 IrqEnMid[7:0]

rw,0000000,sys

RegIrqEnLow

h0045 IrqEnLow[7:0]

rw,0000000,sys

RegIrqPriority

h0046 IrqPriority[7:0]

r,11111111,sys

RegIrqIrq

h0047

r0 IrqHig

r,0,sys IrqMid

r,0,sys IrqLow

r,0,sys

Table 4-10. Interrupt handler registers

The origin of the different interrupts is summarised in the table below.

Event Event source

CntIrqA Counter/Timer A (counter block)

CntIrqB Counter/Timer B (counter block)

CntIrqC Counter/Timer C (counter block)

CntIrqD Counter/Timer D (counter block)

128Hz Low prescaler (clock block)

1Hz Low prescaler (clock block)

PAIrq[7:0] Port A

UartIrqRx UART reception

UartIrqTx UART transmission

UrstCond1 USRT condition 1

UsrtCond2 USRT condition 2

VldIrq Voltage level detector

IrqAC Acquisition chain end of conversion interrupt

Table 4-11. Interrupt source description

4-7

XE8805/05A

4.2.9 USRT (h0048-h004F)

Name

Address

RegUsrtS1

h0048

r0 UsrtS1

s,1,sys

RegUsrtS0

h0049

r0 UsrtS0

s,1,sys

RegUsrtCond1

h004A

r0 UsrtCond1

rc,0,sys

RegUsrtCond2

h004B

r0 UsrtCond2

rc,0,sys

RegUsrtCtrl

h004C

r0 UsrtWaitS0

r,0,sys UsrtEnWaitCond1

rw,0,sys UsrtEnWaitS0

rw,0,sys UsrtEnable

rw,0,sys

RegUsrtBufferS1

h004D

r0 UsrtBufferS1

r,0,sys

RegUsrtEdgeS0

h004E

r0 UsrtEdgeS0

r,0,sys

Table 4-12. USRT register description

4.2.10 UART (h0050-h0057)

Name

Address

RegUartCtrl

h0050 UartEcho

rw,0,sys UartEnRx1

rw,0,sys UartEnTx

rw,0,sys UartXRx

rw,0,sys UartXTx

rw,0,sys UartBR[2:0]

rw,101,sys

RegUartCmd

h0051 SelXtal

rw,0,sys UartEnRx2

rw,0,sys UartRcSel[2:0]

rw,000,sys UartPM

rw,0,sys UartPE

rw,0,sys UartWL

rw,1,sys

RegUartTx

h0052 UartTx[7:0]

rw,0000000,sys

RegUartTxSta

h0053

r0 UartTxBusy

r,0,sys UartTxFull

r,0,sys

RegUartRx

h0054 UartRx[7:0]

r,00000000,sys

RegUartRxSta

h0055

r0 UartRxSErr

r,0,sys UartRxPErr

r,0,sys UartRxFErr

r,0,sys UartRxOerr

rc,0,sys UartRxBusy

r,0,sys UartRxFull

r,0,sys

Table 4-13. UART register description

4.2.11 Counter/Timer/PWM registers (h0058-h005F)

Name

Address

RegCntA

h0058 CounterA[7:0]

s,xxxxxxxx,-

RegCntB

h0059 CounterB[7:0]

s,xxxxxxxx,-

RegCntC

h005A CounterC[7:0]

s,xxxxxxxx,-

RegCntD

h005B CounterD[7:0]

s,xxxxxxxx,-

RegCntCtrlCk

h005C CntDCkSel[1:0]

rw,xx,- CntCCkSel[1:0]

rw,xx,- CntBCkSel[1:0]

rw,xx,- CntACkSel[1:0]

rw,xx,-

RegCntConfig1

h005D CntDDownUp

rw,x,- CntCDownUp

rw,x,- CntBDownUp

rw,x,- CntADownUp

rw,x,- CascadeCD

rw,x,- CascadeAB

rw,x,- CntPWM1

rw,0,sys CntPWM0

rw,0,sys

RegCntConfig2

h005E CapSel[1:0]

rw,00,sys CapFunc[1:0]

rw,00,sys Pwm1Size[1:0]

rw,xx,- Pwm0Size[1:0]

rw,xx,-

RegCntOn

h005F

r0 CntDEnable

rw,0,sys CntCEnable

rw,0,sys CntBEnable

rw,0,sys CntAEnable

rw,0,sys

Table 4-14. Counter/timer/PWM register description.

4-8

XE8805/05A

4.2.12 Acquisition chain registers (h0060-h0067)

Name

Address

RegAcOutLsb

h0060 OUT[7:0]

r,0,sys

RegAcOutMsb

h0061 OUT[15:8]

r,0,sys

RegAcCfg0

h0062 START

w r0,0,sys SET_NELCONV[1:0]

rw,01,sys SET_OSR[2:0]

rw,010,sys CONT

rw,0,sys

RegAcCfg1

h0063 IB_AMP_ADC[1:0]

rw,11,sys IB_AMP_PGA[1:0]

rw,11,sys ENABLE[3:0]

rw,0000,sys

RegAcCfg2

h0064 FIN

rw,00,sys PGA2_GAIN[1:0]

rw,00,sys PGA2_OFFSET[3:0]

rw,0000,sys

RegAcCfg3

h0065 PGA1_GAIN

Rw,0,sys PGA3_GAIN[6:0]

rw,0000000,sys

RegAcCfg4

h0066

r0 PGA3_OFFSET

rw,0000000,sys

RegAcCfg5

h0067 BUSY

r,0,sys DEF

w r0 AMUX[4:0]

rw,00000,sys VMUX

rw,0,sys

Table 4-15. Acquisition chain register description.

4.2.13 Signal D/A registers (h0074-h0077)

Name

Address

RegDasInLsb

h0074 DasInLsb(7:0)

rw,00000000,sys

RegDasInMsb

h0075 DasInMsb(7:0)

rw,00000000,sys

RegDasCfg0

h0076 NsOrder(1:0)

rw,00,sys CodeLmax(2:0)

rw,000,sys Enable(1:0)

rw,00,sys Fin

rw,0,sys

RegDasCfg1

h0077

r0 BW

rw,0,sys Inv

rw,0,sys

Table 4-16. Signal D/A register description

4.2.14 Bias D/A registers (h0078-h0079)

Name

Address

RegDabIn

h0078 DabIn(7:0)

rw,00000000,sys

RegDabCfg

h0079

r0 Enable(1:0)

rw,00,sys

Table 4-17. Bias D/A register description

4.2.15 Voltage multiplier (h007C)

Name

Address

RegVmultCfg0

h007C

r0 Enable

rw,0,sys Fin[1:0]

rw,00,sys

Table 4-18. VMULT register.

4-9

XE8805/05A

4.2.16 Voltage Level Detector registers (h007E-h007F)

Name

Address

RegVldCtrl

h007E

r0 VldRange

rw,0,sys VldTune[2:0]

rw,000,sys

RegVldStat

h007F

r0 VldResult

r,0,sys VldValid

r,0,sys VldEn

rw,0,sys

Table 4-19. Voltage level detector register description

4.2.17 RAM (h0080-h027F)

The 512 RAM bytes can be accessed for read and write operations. The RAM has no reset function. Variables

stored in the RAM should be initialised before use since they can have any value at circuit start up.

5-1

XE8805/05A

5 System Block

5.1 Overview 5-2

5.2 Operating mode 5-2

5-2

XE8805/05A

5.1 Overview

The XE8000 chips have three operating modes. There is the normal, the low current and the very low current

modes (see Figure 5-1). The different modes are controlled by the reset and clock blocks (see the documentation

of the respective blocks).

5.2 Operating mode

Start-up

All bits are reset in the design when a POR (power-on-reset) is active.

RC is enabled, Xtal is disabled and the CPU is reset (pmaddr = 0000).

If Port A is used to return from the sleep mode, all bits with resetcold don’t change (see sleep mode).

Reset

All bits with resetsystem and resetpconf (if enabled) are reset. Clock configuration doesn’t change except cpuck.

The CPU is reset.

Active mode

This is the mode where the CPU and all peripherals can work and execute the embedded software.

Standby mode

Executing a HALT instruction moves the XE8805 into the Standby mode. The CPU is stopped, but the clocks

remain active. Therefore, the enabled peripherals remain active e.g. for time keeping. A reset or an interrupt/event

request (if enabled) cancels the standby mode.

Sleep mode

This is a very low-power mode because all circuit clocks and all peripherals are stopped. Only some service blocks

remain active. No time-keeping is possible. Two instructions are necessary to move into sleep mode. First, the

SleepEn (sleep enable) bit in RegSysCtrl has to be set to 1. The sleep mode can then be activated by setting the

Sleep bit in RegSysReset to 1.

There are three possibe ways to wake-up from the sleep mode:

1. The por (power-on-reset caused by a power-down followed by power-on). The RAM information is lost.

2. The padreset

3. The Port A reset combination (if the Port A is present in the product). See Port A documentation for

more details.

Note: If the Port A is used to return from the sleep mode, all bits with resetcold don’t change (RegSysCtrl,

RegSysReset (except bit sleep), EnExtClock and BiasRc in RegSysClock, RegSysRcTrim1 and

RegSysRcTrim2). The SleepFlag bit in RegSysReset, reads back a 1 if the circuit was in sleep mode

since the flag was last cleared (see reset block for more details).

Note: For a lower power consumption, disable the BiasRc bit in RegSysClock before to going to sleep mode.

The start-up time of the oscillator will then be longer however.

Note: It is recommended to insert a NOP instruction after the instruction that sets the circuit in sleep mode

because this instruction can be executed when the sleep mode is left using the resetfromportA.

5-3

XE8805/05A

START-UP

RESET

ACTIVE STAND-BY SLEEP

Halt instruct ion

Interrupt/event

set bit sleep

padreset

portA reset

normal mode low current very low current

padreset

portA reset

watchdog reset

buserror reset

padreset

portA reset

watchdog reset

por

without

condition

without

condition

Figure 5-1. XE8805 operating modes.

6-1

XE8805/05A

6 Reset Block

6.1 Features 6-2

6.2 Overview 6-2

6.3 Register map 6-2

6.4 Reset handling capabilities 6-3

6.5 Reset source description 6-4

6.5.1 Power On Reset 6-4

6.5.2 RESET pin 6-4

6.5.3 Programmable Port A input combination 6-4

6.5.4 Watchdog reset 6-4

6.5.5 BusError reset 6-4

6.5.6 Sleep mode 6-4

6.6 Control register description and operation 6-4

6.7 Watchdog 6-5

6.8 Start-up and watchdog specifications 6-5

6-2

XE8805/05A

6.1 Features

• Power On Reset (POR)

• External reset from the RESET pin

• Programmable Watchdog timer reset

• Programmable BusError reset

• Sleep mode management

• Programmable Port A input combination reset

6.2 Overview

The reset block is the reset manager. It handles the different reset sources and distributes them through the

system. It also controls the sleep mode of the circuit.

6.3 Register map

Pos. RegSysCtrl Rw Reset Function

7 SleepEn r w 0 resetcold enables Sleep mode

0: sleep mode is disabled

1: sleep mode is enabled

6 EnResPConf r w 0 resetcold enables the resetpconf signal when the

resetglobal is active

0: resetpconf is disabled

1: resetpconf is enabled

5 EnBusError r w 0 resetcold enables reset from BusError

0: BusError reset source is disabled

1: BusError reset source is enabled

4 EnResWD r w 0 resetcold enables reset from Watchdog

0: Watchdog reset source is disabled

1: Watchdog reset source is enabled

this bit can not be set to 0 by SW

3 – 0 - r 0000 unused

Table 6-1. RegSysCtrl register.

Pos. RegSysReset Rw Reset Function

7 Sleep rw 0 resetsystem Sleep mode control (reads always 0)

6 - r 0 unused

5 ResetBusError r c 0 resetcold reset source was BusError

4 ResetWD r c 0 resetcold reset source was Watchdog

3 ResetfromportA r c 0 resetcold reset source was Port A combination

2 ResPad r c 0 resetcold reset source was reset pad

1 ResPadSleep r c 0 resetcold reset source was reset pad in sleep mode

0 - r 0 unused

Table 6-2. RegSysReset register

6-3

XE8805/05A

Pos. RegSysWD Rw Reset Function

7 – 4 - r 0000 unused

WDKey[3] w Watchdog Key bit 3

3 WDCounter[3] r 0 resetcold Watchdog counter bit 3

WDKey[2] w Watchdog Key bit 2

2 WDCounter[2] r 0 resetcold Watchdog counter bit 2

WDKey[1] w Watchdog Key bit 1

1 WDCounter[1] r 0 resetcold Watchdog counter bit 1

WDKey[0] w Watchdog Key bit 0

0 WDCounter[0] r 0 resetcold Watchdog counter bit 0

Table 6-3. RegSysWD register

6.4 Reset handling capabilities

There are 5 reset sources:

• Power On Reset (POR)

• External reset from the RESET pin

• Programmable Port A input combination

• Programmable watchdog timer reset

• Programmable BusError reset on processor access outside the allocated memory map

Another reset source is the bit Sleep in the RegSysReset register. This source is fully controlled by software and

is only used during the sleep mode.

Four internal reset signals are generated from these sources and distributed through the system:

• resetcold: is asserted on POR

• resetsystem: is asserted when resetcold or any other enabled reset source is active

• resetpconf: is asserted when resetsystem is active and if the EnResPConf bit in the RegSysCtrl register

is set. This reset is generally used in the different ports. It allows to maintain the port

configuration unchanged while the rest of the circuit is reset.

• resetsleep: is asserted when the circuit is in sleep mode

For the circuits XE8801A and XE8805A

(2) For the circuits XE8801 and XE8805

Table 6-4 shows a summary of the dependency of the internal reset signals on the various reset sources. In all the

tables describing the different registers, the reset source is indicated.

Internal reset signals

resetpconf

Asserted

reset source resetsystem when

EnResPConf=0 when

EnResPConf=1 resetsleep resetcold

POR Asserted Asserted Asserted Asserted Asserted

RESET pin (1) Asserted Asserted Asserted Asserted Asserted

RESET pin (2) Asserted - Asserted - -

PortA input Asserted - Asserted - -

Watchdog Asserted - Asserted - -

BusError Asserted - Asserted - -

Sleep - - - Asserted -

(1) For the circuits XE8801A and XE8805A

(2) For the circuits XE8801 and XE8805

Table 6-4. Internal reset assertion as a function of the reset source.

6-4

XE8805/05A

6.5 Reset source description

6.5.1 Power On Reset

The power on reset (POR) monitors the external supply voltage. It activates a reset on a rising edge of this supply

voltage. The reset is inactivated only if the internal voltage regulator has started up. No precise voltage level

detection is performed by the POR block.

6.5.2 RESET pin

The reset can be activated by applying a high input state on the RESET pin.

6.5.3 Programmable Port A input combination

A reset signal can be generated by Port A. See the description of the Port A for further information.

6.5.4 Watchdog reset

The Watchdog will generate a reset if the EnResetWD bit in the RegSysCtrl register has been set and if the

watchdog is not cleared in time by the processor. See chapter 6.7 describing the watchdog for further information.

6.5.5 BusError reset

The address space is assigned as shown in the register map of the product. If the EnBusError bit in the

RegSysCtrl register is set and a non-existant address is accessed by the software, a reset is generated.

6.5.6 Sleep mode

Entering the sleep mode will reset a part of the circuit. The reset is used to configure the circuit for correct wake-up

after the sleep mode. If the SleepEn bit in the RegSysCtrl register has been set, the sleep mode can be entered

by setting the bit Sleep in RegSysReset. During the sleep mode, the resetsleep signal is active. For detailed

information on the sleep mode, see the system documentation.

6.6 Control register description and operation

Two registers are dedicated for reset status and control, RegSysReset and RegSysCtrl. The bits Sleep, and

SleepEn are also located in those registers and are described in the chapter dedicated to the different operating

modes of the circuit (system block).

The RegSysReset register gives information on the source which generated the last reset. It can be read at the

beginning of the application program to detect if the circuit is recovering from an error or exception condition, or if

the circuit is starting up normally.

• when ResBusError is 1, a forbidden address access generated the reset.

• when ResWD is 1, the watchdog generated the reset.

• when ResPortA is 1, a PortA combination generated the reset.

• when ResPad is 1, a reset pin generated the reset.

• when ResPadSleep is 1, a reset pin in sleep mode generated the reset.

Note: If no bit is set to 1, the reset source was the internal POR.

Note: Several bits might be set or not, if the register was not cleared in between 2 reset occurrences. Write

any value in RegSysReset to clear it.

Note: When a reset pin wakes up the chip from the sleep mode, ResPad and ResPadSleep bits are equal

at 1.

The last bit concerns the sleep mode control (see system documentation for the sleep mode description).

6-5

XE8805/05A

• when Sleep is set to 1, and SleepEn is 1, the sleep mode is entered. The bit always reads back a 0.

The RegSysCtrl register enables the different available reset sources and the sleep mode.

• EnResWD enables the reset due to the watchdog (can not be disabled once enabled).

• EnBusError enables the reset due to a bus error condition.

• EnResPConf enables the reset of the port configurations when reset by Port A, a Bus Error or the

watchdog.

• SleepEn unlocks the Sleep bit. As long as SleepEn is 0, the Sleep bit has no effect.

6.7 Watchdog

The watchdog is a timer which has to be cleared at least every 2 seconds by the software to prevent a reset being

generated by the timeout condition.

The watchdog can be enabled by software by setting the EnResWD bit in the RegSysCtrl register to 1. It can then

only be disabled by a power on reset.

The watchdog timer can be cleared by writing consecutively the values Hx0A and Hx03 to the RegSysWD register.

The sequence must strictly be respected to clear the watchdog.

In assembler code, the sequence to clear the watchdog is:

move AddrRegSysWD, #0x0A

move AddrRegSysWD, #0x03

Only writing Hx0A followed by Hx03 resets the WD. If some other write instruction is done to the RegSysWD

between the writing of the Hx0A and Hx03 values, the watchdog timer will not be cleared.

It is possible to read the status of the watchdog in the RegSysWD register. The watchdog is a 4 bit counter with a

count range between 0 and 7. The system reset is generated when the counter is reaching the value 8.

6.8 Start-up and watchdog specifications

At start-up of the circuit, the POR (power-on-reset) block generates a reset signal during tPOR. The circuit starts

software execution after this period (see system chapter). The POR is intended to force the circuit in a correct state

at start-up. For precise monitoring of the supply voltage, the voltage level detector (VLD) has to be used.

6-6

XE8805/05A

Symbol Parameter Min Typ Max Unit Comments

TPOR POR reset duration 5 20 ms

TRESET RESET pin reset duration 20 200 µs 3

TRESET RESET pin reset duration 5 20 ms 4

Vbat_sl_M Supply ramp up of MTP version 20 V/ms 1

Vbat_sl_R Supply ramp up of ROM version 0.25 V/ms 1

WDtime Watchdog timeout period 2 s 2

Table 6-5. Electrical and timing specifications

Note: 1) The Vbat_sl defines the minimum slope required on VBAT. Correct start-up of the circuit is not guaranteed

if this slope is too slow. In such a case, a delay has to be built using the RESET pin.

Note: 2) The minimal watchdog timeout period is guaranteed when the internal oscillators are used. The watchdog

takes its clock from the low prescaler. In case an external clock source is used, the RC oscillator must be enabled

also (EnRC=1 in RegSysClock). Otherwise, the watchdog is stopped (see the clock block documentation).

Note: 3) For the circuit versions XE8801 and XE8805. Gives the time the reset is active after the falling edge of the

RESET pin.

Note: 4) For the circuit versions XE8801A and XE8805A. Gives the time the reset is active after the falling edge of

the RESET pin.

7-1

XE8805/05A

7 Clock Generator

7.1 Features 7-2

7.2 Overview 7-2

7.3 Register map 7-2

7.4 Interrupts and events map 7-3

7.5 Clock sources 7-4

7.5.1 RC oscillator 7-4

7.5.2 Xtal oscillator 7-6

7.5.3 External clock 7-7

7.6 Clock source selection 7-8

7.7 RegSysMisc Description 7-8

7.8 Prescalers 7-9

7.9 32 kHz frequency selector 7-9

7-2

XE8805/05A

7.1 Features

• 3 available clock sources (RC oscillator, quartz oscillator and external clock).

• 2 divider chains: high-prescaler (8 bits) and low-prescaler (15 bits).

• CPU clock disabling in halt mode.

7.2 Overview

The XE8805 chips can work on different clock sources (RC oscillator, quartz oscillator and external clock). The

clock generator block is in charge of distributing the necessary clock frequencies to the circuit. Figure 7-1

represents the functionality of the clock block.

The internal RC oscillator drives the high prescaler. This prescaler generates frequency divisions down to 1/256 of

its input frequency. A 32kHz clock is generated by enabling the quartz oscillator (if present in the product) or by

selecting the appropriate tap on the high prescaler. The low prescaler generates clock signals from 32kHz down to

1Hz. The clock source for the CPU can be selected from the RC oscillator, the external clock or the 32kHz clock.

7.3 Register map

pos. RegSysClock rw Reset function

7 CpuSel rw 0 resetsleep Select speed for cpuck, 0=RC, 1=xtal or

external clock

6 Extclk r 0 resetcold External clock detected, 1=available

5 EnExtClock rw 0 resetcold Enable for external clock, 1=enabled

4 BiasRc rw 1 resetcold Enable Rcbias (reduces start-up time of RC).

3 ColdXtal r 1 resetsleep Xtal in start phase

2 ColdRC r 1 resetsleep RC in start phase

1 EnableXtal rw 0 resetsleep Enable Xtal oscillator, 0=disabled, 1=enabled

0 EnableRc rw 1 resetsleep Enable RC oscillator, 0=disabled, 1=enabled

Table 7-1: RegSysClock register

pos. RegSysMisc rw Reset Function

7-4 -- r 0000 Unused

3 RCOnPA0 rw 0 resetsleep Start RC on PA[0], 0=disabled, 1=enabled

2 DebFast rw 0 resetsleep Debouncer clock speed, 0=256Hz, 1=8kHz

1 OutputCkXtal rw 0 resetsleep Output Xtal Clock on PB[3], 0=disabled,

1=enabled if EnXtal=1 else PB[3]=0

0 OutputCpuCk rw 0 resetsleep Output CPU clock on PB[2], 0=disabled,

1=enabled

Table 7-2: RegSysMisc register

pos. RegSysPre0 rw reset Function

7-1 -- r 0000000 Unused

0 ResPre w1

r0 0 Write 1 to reset low prescaler, but always

Table 7-3: RegSysPre0 register

7-3

XE8805/05A

pos. RegSysRcTrim1 rw reset Function

7-4 -- r 00 Unused

5 Reserved rw 0 resetcold Reserved

4 RcFreqRange rw 0 resetcold Low/high freq. range (low=0)

3 RcFreqCoarse[3] rw 0 resetcold RC coarse trim bit 3

2 RcFreqCoarse[2] rw 0 resetcold RC coarse trim bit 2

1 RcFreqCoarse[1] rw 0 resetcold RC coarse trim bit 1

0 RcFreqCoarse[0] rw 0 resetcold RC coarse trim bit 0

Table 7-4: RegSysRCTrim1 register

pos. RegSysRcTrim2 Rw reset function

7-6 -- r 00 Unused

5 RcFreqFine[5] rw 1 resetcold RC fine trim bit 5

4 RcFreqFine[4] rw 0 resetcold RC fine trim bit 4

3 RcFreqFine[3] rw 0 resetcold RC fine trim bit 3

2 RcFreqFine[2] rw 0 resetcold RC fine trim bit 2

1 RcFreqFine[1] rw 0 resetcold RC fine trim bit 1

0 RcFreqFine[0] rw 0 resetcold RC fine trim bit 0

Table 7-5: RegSysRCTrim2 register

OSCIN

Xtal

High prescaler

CpuCk

CpuSel

RegSysRcTrim1

RegSysRcTrim2

CkRc

CkXtal

EnXtal and

not(ExtClk or EnExtClk)

Low prescaler 32kHz

1Hz

CkRc

CkRc/256

External

Clock 0

Figure

7-1. Clock block structure

7.4 Interrupts and events map

Interrupt Interrupt source Mapping in the interrupt manager Mapping in the event manager

IrqPre1 Ck128Hz RegIrqHig(6) RegEvn(5)

IrqPre2 Ck1Hz RegIrqMid(3) RegEvn(1)

Table 7-6: Interrupts and events map

7-4

XE8805/05A

7.5 Clock sources

7.5.1 RC oscillator

7.5.1.1 Configuration

The RC oscillator is always turned on and selected for CPU and system operation at power-on reset and when

exiting sleep mode. It can be turned off after the Xtal (quartz oscillator) has been started, after selection of the

external clock or by entering sleep mode.

The RC oscillator has two frequency ranges: sub-MHz (100 kHz to 1 MHz) and above-MHz (1 MHz to 10 MHz).

Inside a range, the frequency can be tuned by software for coarse and fine adjustment. See registers

RegSysRcTrim1 and RegSysRcTrim2.

Bit EnableRC in register RegSysClock controls the propagation of the RC clock signal and the operation of the

oscillator. The user can stop the RC oscillator by resetting the bit EnableRC. Entering the sleep mode disables the

RC oscillator.

Note: Before turning off the RC oscillator, the cpusel bit in RegSysClock must be set to one.

Note: The RC oscillator bias can be maintained while the oscillator is switched off by setting the bit BiasRc in

RegSysClock. This allows a faster restart of the RC oscillator at the cost of increased power consumption when

the oscillator is disabled (see section 7.5.1.3).

7.5.1.2 RC oscillator frequency tuning

The RC oscillator frequency can be set using the bits in the RegSysRcTrim1 and RegSysRcTrim2 registers.

Figure 7-2 shows the nominal frequency of the RC oscillator as a function of these bits. The absolute value of the

frequency for a given register content may change by ±50% from chip to chip due to the tolerances on the

integrated capacitors and resistors. However, the modification of the frequency as a function of a modification of

the register content is fairly precise for frequencies below 2MHz. This means that the curves in Figure 7-2 can shift

up and down but that the slope remains unchanged.

The bit RcFreqRange modifies the oscillator frequency by a factor of 10. The upper curve in the figure

corresponds to RcFreqRange=1.

The RcFreqCoarse modifies the frequency of the oscillator by a factor (RcFreqCoarse+1). The figure represents

the frequency for 5 different values of the bits RcFreqCoarse: for each value the frequency is multiplied by 2.

Incrementing the RcFreqFine code increases the frequency by about 1.4%.

The frequency of the oscillator is therefor given by:

RC=fRcmin⋅(1+9⋅RcFreqRange)⋅(1+RcFreqCoarse)⋅(1.014)RcFreqFine

with fRcmin the RC oscillator frequency if the registers are all 0. At higher frequencies, the frequency may deviate

from the value predicted by the equation.

7-5

XE8805/05A

000000

010000

100000

110000

111111

010000

100000

110000

111111

010000

100000

110000

111111

010000

100000

110000

111111

010000

100000

110000

111111

000000

010000

100000

110000

111111

010000

100000

110000

111111

010000

100000

110000

111111

010000

100000

110000

111111

010000

100000

110000

111111

0000 0001 0011 0111 1111

1E+04

1E+05

1E+06

1E+07

1E+08

RcFreqCoarse(3:0)

Nominal RC oscillator frequency [Hz]

RcFreqRange='1'

RcFreqRange='0'

RcFreqFine(5:0)

Figure 7-2. RC oscillator nominal frequency tuning.

7.5.1.3 RC oscillator specifications

symbol description min typ max unit Comments

fRCmin Lowest RC frequency 40 80 120 kHz Note 1

RcFreqFine fine tuning step 1.4 2.0 %

RC_su startup time 30 50 us

BiasRc=0

3 5 us

BiasRc=1

PSRR @ DC Supply voltage TBD %/V Note 2

dependence TBD %/V Note 3

∆f/∆T Temperature

dependence 0.1

%/°C

Table 7-7. RC oscillator specifications

Note 1: this is the frequency tolerance when all trimming codes are 0.

Note 2: frequency shift as a function of VBAT with normal regulator function.

Note 3: frequency shift as a function of VBAT while the regulator is short-circuited to VBAT.

The tolerances on the minimal frequency and the drift with supply or temperature can be cancelled using the

software DFLL (digital frequency locked loop) which uses the crystal oscillator as a reference frequency.

7-6

XE8805/05A

7.5.2 Xtal oscillator

7.5.2.1 Xtal configuration

The Xtal operates with an external crystal of 32’768 Hz.

During Xtal oscillator start-up, the first 32768 cycles are masked. The two bits EnableXtal and ColdXtal in register

RegSysClock control the oscillator.

At power-on reset or during sleep mode, EnableXtal is reset and ColdXtal is set (Xtal oscillator is not selected at

start-up). The user can start Xtal oscillator by setting EnableXtal. When the Xtal oscillator starts, bit ColdXtal is

reset after 32768 cycles. Before ColdXtal is reset by the system, the Xtal frequency precision is not guaranteed.

The Xtal oscillator can be stopped by the user by resetting bit EnableXtal.

When the user enters into sleep mode, the Xtal is stopped.

When an external clock is detected (ExtClk = 1) or the EnExtClock is set 1, the EnableXtal bit can not be set to 1.

7.5.2.2 Xtal oscillator specifications

The crystal oscillator has been designed for a crystal with the specifications given in Table 7-8. The oscillator

precision can only be guaranteed for this crystal.

Symbol Description Min Typ Max Unit Comments

Fs Resonance frequency 32768 Hz

CL CL for nominal

frequency 8.2 15 pF

Rm Motional resistance 40 100

kΩ

Cm Motional capacitance 1.8 2.5 3.2 fF

C0 Shunt capacitance 0.7 1.1 2.0 pF

Rmp Motional resistance of

6th overtone (parasitic) 4 8

kΩ

Q Quality factor 30k 50k 400k -

Table 7-8. Crystal specifications.

For safe operation, low power consumption and to meet the specified precision, careful board layout is required:

Keep lines OSCIN and OSCOUT short and insert a VSS line in between them.

Connect the crystal package to VSS.

No noisy or digital lines near OSCIN or OSCOUT.

Insert guards where needed.

Respect the board specifications of Table 7-9.

Symbol Description Min Typ Max Unit Comments

Rh_oscin Resistance OSCIN-VSS 10

MΩ

Rh_oscout Resistance OSCOUT-VSS 10

MΩ

Rh_oscin_oscout Resistance OSCIN-OSCOUT 50

MΩ

Cp_oscin Capacitance OSCIN-VSS 0.5 3.0 pF

Cp_oscout Capacitance OSCOUT-VSS 0.5 3.0 pF

Cp_oscin_oscout Capacitance OSCIN-OSCOUT 0.2 1.0 pF

Table 7-9. Board layout specifications.

The oscillator characteristics are given in Table 7-10. The characteristics are valid only if the crystal and board

layout meet the specifications above.

7-7

XE8805/05A

Symbol Description Min Typ Max Unit Comments

fXtal Nominal frequency 32768 Hz

St_xtal Start-up time 1 2 s

Fstab Frequency deviation -100 300 ppm Note 1

Table 7-10. Crystal oscillator characteristics.

Note 1. This gives the relative frequency deviation from nominal for a crystal with CL=8.2pF and within the

temperature range -40°C to 85°C. The crystal tolerance, crystal aging and crystal temperature drift are not included

in this figure.

7.5.3 External clock

7.5.3.1 External clock configuration

The user can provide an external clock instead of the internal oscillators. Only the CPU can use the external clock.

The external clock input pin is OSCIN.

The system is configured for external clock by bit EnExtClock in register RegSysClock.

When EnExtClock is set to 1, the external clock is detected after 4 pulses on pin OSCIN. The ExtClk bit shows

when the external clock is available.

Note: when using the external clock, the Xtal is not available.

7.5.3.2 External clock specification

The external clock has to satisfy the specifications in the table below. Correct behavior of the circuit can not be

guaranteed if the external clock signal does not respect the specifications below.

Symbol Description Min Typ Max Unit Comments

FEXT External clock

frequency 2 MHz

PW_1 Pulse 1 width 0.2 µs

PW_0 Pulse 0 width 0.2 µs

Table 7-11. External clock specifications.

7-8

XE8805/05A

7.6 Clock source selection

There are three possible clock sources available for the CPU clock. The RC clock is always selected after power-

up or after Sleep mode. The CPU clock selection is done with the bit CpuSel in RegSysClock (0= RC clock, 1= 32

kHz from Xtal if EnableXtal =1, ExtClk = 0 and EnExtClk = 0 else external clock).

Switching from one clock source to another is glitch free.

The next table summarizes the different clock configurations of the circuit:

Clock Sources Clock targets

Cpuck Note 1

Mode

name

EnExtClk

EnableRc

EnableXtal

CpuSel=0 CpuSel=1

High

Prescaler

Clock

input

Low

Prescaler

Clock

input

Sleep 0 0 0 Off Off Off Off

Xtal 0 0 1 Off Xtal Off Xtal

RC 0 1 0 RC RC RC High presc.

RC + Xtal 0 1 1 RC Xtal RC Xtal

External 1 0 X Off External Off Off

RC +

External 1 1 X RC External RC High presc.

Table 7-12: Table of clocking modes.

Note 1: The CPU clock can be divided by using the freq instruction (see coolrisc instruction set)

Switching from one clock source to another and stopping the unused clock source must be performed using 3

MOVE instructions to RegSysClock. First select the new clock source, secondly change the CpuSel bit and finally

stop the unused one.

7.7 RegSysMisc Description

The RCOnPA0 bit in RegSysMisc can be used to enable the RC oscillator on an event external to the circuit. If

RCOnPA0 is 1, the RC oscillator is enabled (EnableRC bit is set to 1) as soon as the value on port A pin PA[0] is

equal to 1. The port A pin can be debounced (see port A documentation).

Bit DebFast in the RegSysMisc register allows to chose the debouncer clock between 256Hz and 8kHz (DebFast

= 0 and DebFast = 1 respectively). The Debouncer clock is used to debounce PA inputs (see port A

documentation).

Bit OutputCkXtal allows to show the Xtal clock on PB[3]. The EnableXtal bit must be set to 1 else PB[3] equals 0

(see port B documentation to set up the port B).

Bit OutputCpuCk allows to show the CpuClock on PB[2] (see port B documentation).

7-9

XE8805/05A

7.8 Prescalers

The clock generator block embeds two divider chains: the high prescaler and the low prescaler.

The high prescaler is made of an 8 stage dividing chain and the low prescaler of a 15 stage dividing chain.

Features:

• High prescaler can only be driven with RC clock (bit EnableRc have to be set, see Table 7-12).

• Low prescaler can be driven from the high prescaler or directly with the Xtal clock when bit EnableXtal is set to

1, bit EnExtClock is set to 0 and ExtClk is equal at 0.

• Bit ResPre in the RegSysPre0 register allows to reset synchronously the low prescaler, the low prescaler is

also automatically cleared when bit EnableXtal is set. Both dividing chains are reset asynchronously by the

resetsleep signal.

• Bit ColdXtal=1 indicates the Xtal is in its start up phase. It is active for 37268 Xtal cycles after setting

EnableXtal.

7.9 32 kHz frequency selector

A decoder is used to select from the high prescaler the frequency tap that is the closest to 32 kHz to operate the

low prescaler when the Xtal is not running. In this case, the RC oscillator frequency of ±50% will also be valid for

the low prescaler frequency outputs.

8-1

XE8805/05A

8 IRQ - Interrupt handler

8.1 Features 8-2

8.2 Overview 8-2

8.3 Register map 8-2

8-2

XE8805/05A

8.1 Features

The XE8000 chips support 24 interrupt sources, divided into 3 levels of priority.

8.2 Overview

A CPU interruption is generated and memorized when an interrupt becomes active. The 24 interrupt sources are

divided into 3 levels of priority: High (8 interrupt sources), Mid (8 interrupt sources), and Low (8 interrupt sources).

Those 3 levels of priority are directly mapped to those supported by the CoolRisc® (IN0, IN1 and IN2; see

CoolRisc® documentation for more information).

RegIrqHig, RegIrqMid, and RegIrqLow are 8-bit registers containing flags for the interrupt sources. Those flags

are set when the interrupt is enabled (i.e. if the corresponding bit in the registers RegIrqEnHig, RegIrqEnMid or

RegIrqEnLow is set) and a rising edge is detected on the corresponding interrupt source.

Once memorized, an interrupt flag can be cleared by writing a ‘1’ in the corresponding bit of RegIrqHig, RegIrqMid

or RegIrqLow. Writing a ‘0’ does not modify the flag. To definitively clear the interrupt, one has to clear the

CoolRisc interrupt in the CoolRisc status register. All interrupts are automatically cleared after a reset.

Two registers are provided to facilitate the writing of interrupt service software. RegIrqPriority contains the number

of the highest priority interrupt set (its value is 0xFF when no interrupt is set). RegIrqIrq indicates the priority level

of the current interrupts. RegIrqIrq and RegIrqPriority ‘s values are dependent upon the memorized state of the

interrupts (as reflected in flags in RegIrqHig, RegIrqMid and RegIrqLow).

8.3 Register map

pos. RegIrqHig rw reset function

7 RegIrqHig[7] r

c1 0 resetsystem interrupt #23 (high priority)

clear interrupt #23 when 1 is written

6 RegIrqHig[6] r

c1 0 resetsystem interrupt #22 (high priority)

clear interrupt #22 when 1 is written

5 RegIrqHig[5] r

c1 0 resetsystem interrupt #21 (high priority)

clear interrupt #21 when 1 is written

4 RegIrqHig[4] r

c1 0 resetsystem interrupt #20 (high priority)

clear interrupt #20 when 1 is written

3 RegIrqHig[3] r

c1 0 resetsystem interrupt #19 (high priority)

clear interrupt #19 when 1 is written

2 RegIrqHig[2] r

c1 0 resetsystem interrupt #18 (high priority)

clear interrupt #18 when 1 is written

1 RegIrqHig[1] r

c1 0 resetsystem interrupt #17 (high priority)

clear interrupt #17 when 1 is written

0 RegIrqHig[0] r

c1 0 resetsystem interrupt #16 (high priority)

clear interrupt #16 when 1 is written

Table 8-1: RegIrqHig

8-3

XE8805/05A

pos. RegIrqMid rw reset function

7 RegIrqMid[7] r

c1 0 resetsystem interrupt #15 (mid priority)

clear interrupt #15 when 1 is written

6 RegIrqMid[6] r

c1 0 resetsystem interrupt #14 (mid priority)

clear interrupt #14 when 1 is written

5 RegIrqMid[5] r

c1 0 resetsystem interrupt #13 (mid priority)

clear interrupt #13 when 1 is written

4 RegIrqMid[4] r

c1 0 resetsystem interrupt #12 (mid priority)

clear interrupt #12 when 1 is written

3 RegIrqMid[3] r

c1 0 resetsystem interrupt #11 (mid priority)

clear interrupt #11 when 1 is written

2 RegIrqMid[2] r

c1 0 resetsystem interrupt #10 (mid priority)

clear interrupt #10 when 1 is written

1 RegIrqMid[1] r

c1 0 resetsystem interrupt #9 (mid priority)

clear interrupt #9 when 1 is written

0 RegIrqMid[0] r

c1 0 resetsystem interrupt #8 (mid priority)

clear interrupt #8 when 1 is written

Table 8-2: RegIrqMid

pos. RegIrqLow rw reset function

7 RegIrqLow[7] r

c1 0 resetsystem interrupt #7 (low priority)

clear interrupt #7 when 1 is written

6 RegIrqLow[6] r

c1 0 resetsystem interrupt #6 (low priority)

clear interrupt #6 when 1 is written

5 RegIrqLow[5] r

c1 0 resetsystem interrupt #5 (low priority)

clear interrupt #5 when 1 is written

4 RegIrqLow[4] r

c1 0 resetsystem interrupt #4 (low priority)

clear interrupt #4 when 1 is written

3 RegIrqLow[3] r

c1 0 resetsystem interrupt #3 (low priority)

clear interrupt #3 when 1 is written

2 RegIrqLow[2] r

c1 0 resetsystem interrupt #2 (low priority)

clear interrupt #2 when 1 is written

1 RegIrqLow[1] r

c1 0 resetsystem interrupt #1 (low priority)

clear interrupt #1 when 1 is written

0 RegIrqLow[0] r

c1 0 resetsystem interrupt #0 (low priority)

clear interrupt #0 when 1 is written

Table 8-3: RegIrqLow

pos. RegIrqEnHig rw reset function

7 RegIrqEnHig[7] rw 0 resetsystem 1= enable interrupt #23

6 RegIrqEnHig[6] rw 0 resetsystem 1= enable interrupt #22

5 RegIrqEnHig[5] rw 0 resetsystem 1= enable interrupt #21

4 RegIrqEnHig[4] rw 0 resetsystem 1= enable interrupt #20

3 RegIrqEnHig[3] rw 0 resetsystem 1= enable interrupt #19

2 RegIrqEnHig[2] rw 0 resetsystem 1= enable interrupt #18

1 RegIrqEnHig[1] rw 0 resetsystem 1= enable interrupt #17

0 RegIrqEnHig[0] rw 0 resetsystem 1= enable interrupt #16

Table 8-4: RegIrqEnHig

8-4

XE8805/05A

pos. RegIrqEnMid rw reset function

7 RegIrqEnMid[7] rw 0 resetsystem 1= enable interrupt #15

6 RegIrqEnMid[6] rw 0 resetsystem 1= enable interrupt #14

5 RegIrqEnMid[5] rw 0 resetsystem 1= enable interrupt #13

4 RegIrqEnMid[4] rw 0 resetsystem 1= enable interrupt #12

3 RegIrqEnMid[3] rw 0 resetsystem 1= enable interrupt #11

2 RegIrqEnMid[2] rw 0 resetsystem 1= enable interrupt #10

1 RegIrqEnMid[1] rw 0 resetsystem 1= enable interrupt #9

0 RegIrqEnMid[0] rw 0 resetsystem 1= enable interrupt #8

Table 8-5: RegIrqEnMid

pos. RegIrqEnLow rw reset function

7 RegIrqEnLow[7] rw 0 resetsystem 1= enable interrupt #7

6 RegIrqEnLow[6] rw 0 resetsystem 1= enable interrupt #6

5 RegIrqEnLow[5] rw 0 resetsystem 1= enable interrupt #5

4 RegIrqEnLow[4] rw 0 resetsystem 1= enable interrupt #4

3 RegIrqEnLow[3] rw 0 resetsystem 1= enable interrupt #3

2 RegIrqEnLow[2] rw 0 resetsystem 1= enable interrupt #2

1 RegIrqEnLow[1] rw 0 resetsystem 1= enable interrupt #1

0 RegIrqEnLow[0] rw 0 resetsystem 1= enable interrupt #0

Table 8-6: RegIrqEnLow

pos. RegIrqPriority rw reset function

7-0 RegIrqPriority r 11111111

resetsystem code of highest priority set

Table 8-7: RegIrqPriority

pos. RegIrqIrq rw Reset function

7-3 - r 00000 unused

2 IrqHig r 0 resetsystem one or more high priority interrupt is

set

1 IrqMid r 0 resetsystem one or more mid priority interrupt is

set

0 IrqLow r 0 resetsystem one or more low priority interrupt is

set

Table 8-8: RegIrqIrq

9-1

XE8805/05A

9 Event handler

9.1 Features 9-2

9.2 Overview 9-2

9.3 Register map 9-2

9-2

XE8805/05A

9.1 Features

The XE8000 chips support 8 event sources, divided into 2 levels of priority.

9.2 Overview

A CPU event is generated and memorized when an event source becomes active. The 8 event sources are divided

into 2 levels of priority: High (4 event sources) and Low (4 event sources). Those 2 levels of priority are directly

mapped to those supported by the CoolRisc (EV0 and EV1; see CoolRisc documentation for more information).

RegEvn is an 8-bit register containing flags for the event sources. Those flags are set when the event is enabled

(i.e. if the corresponding bit in the registers RegEvnEn is set) and a rising edge is detected on the corresponding

event source.

Once memorized, writing a ‘1’ in the corresponding bit of RegEvn clears an event flag. Writing a ‘0’ does not

modify the flag. All interrupts are automatically cleared after a reset.

Two registers are provided to facilitate the writing of event service software. RegEvnPriority contains the number

of the highest priority event set (its value is 0xFF when no event is set). RegEvnEvn indicates the priority level of

the current interrupts. RegEvnEvn and RegEvnPriority ‘s values are dependent upon the memorized state of the

events (as reflected in flags in RegEvn).

9.3 Register map

pos. RegEvn rw reset function

7 RegEvn[7] r

c1 0 resetsystem event #7 (high priority)

clear event #7 when written 1

6 RegEvn[6] r

c1 0 resetsystem event #6 (high priority)

clear event #6 when written 1

5 RegEvn[5] r

c1 0 resetsystem event #5 (high priority)

clear event #5 when written 1

4 RegEvn[4] r

c1 0 resetsystem event #4 (high priority)

clear event #4 when written 1

3 RegEvn[3] r

c1 0 resetsystem event #3 (low priority)

clear event #3 when written 1

2 RegEvn[2] r

c1 0 resetsystem event #2 (low priority)

clear event #2 when written 1

1 RegEvn[1] r

c1 0 resetsystem event #1 (low priority)

clear event #1 when written 1

0 RegEvn[0] r

c1 0 resetsystem event #0 (low priority)

clear event #0 when written 1

Table 9-1: RegEvn

9-3

XE8805/05A

pos. RegEvnEn rw reset function

7 RegEvnEn[7] rw 0 resetsystem 1= enable event #7

6 RegEvnEn[6] rw 0 resetsystem 1= enable event #6

5 RegEvnEn[5] rw 0 resetsystem 1= enable event #5

4 RegEvnEn[4] rw 0 resetsystem 1= enable event #4

3 RegEvnEn[3] rw 0 resetsystem 1= enable event #3

2 RegEvnEn[2] rw 0 resetsystem 1= enable event #2

1 RegEvnEn[1] rw 0 resetsystem 1= enable event #1

0 RegEvnEn[0] rw 0 resetsystem 1= enable event #0

Table 9-2: RegEvnEn

pos. RegEvnPriority rw reset function

7-0 RegEvnPriority r 11111111

resetsystem code of highest event set

Table 9-3: RegEvnPriority

pos. RegEvnEvn rw reset function

7-2 - r 00000 unused

1 EvnHig r 0 resetsystem one or more high priority event is set

0 EvnLow r 0 resetsystem one or more low priority event is set

Table 9-4: RegEvnEvn

10-1

XE8805/05A

10 Low power RAM

10.1 Features 10-2

10.2 Overview 10-2

10.3 Register map 10-2

10-2

XE8805/05A

10.1 Features

• Low power RAM locations.

10.2 Overview

In order to save power consumption, 8 8-bit registers are provided in page 0. These memory locations should be

reserved for often-updated variables. Accessing these register locations requires much less power than the other

general purpose RAM locations.

10.3 Register map

pos. Reg00 rw reset function

7-0 Reg00 rw XXXXXXXX low-power data memory

Table 10-1: Reg00

pos. Reg01 rw reset function

7-0 Reg01 rw XXXXXXXX low-power data memory

Table 10-2: Reg01

pos. Reg02 rw reset function

7-0 Reg02 rw XXXXXXXX low-power data memory

Table 10-3: Reg02

pos. Reg03 rw reset function

7-0 Reg03 rw XXXXXXXX low-power data memory

Table 10-4: Reg03

pos. Reg04 rw reset function

7-0 Reg04 rw XXXXXXXX low-power data memory

Table 10-5: Reg04

pos. Reg05 rw reset function

7-0 Reg05 rw XXXXXXXX low-power data memory

Table 10-6: Reg05

pos. Reg06 rw ¨reset function

7-0 Reg06 rw XXXXXXXX low-power data memory

Table 10-7: Reg06

pos. Reg07 rw reset function

7-0 Reg07 rw XXXXXXXX low-power data memory

Table 10-8: Reg07

11-1

XE8805/05A

11 Port A

11.1 Features 11-2

11.2 Overview 11-2

11.3 Register map 11-3

11.4 Interrupts and events map 11-3

11.5 Port A (PA) Operation 11-4

11.6 Port A electrical specification 11-5

11-2

XE8805/05A

11.1 Features

• Input port, 8 bits wide

• Each bit can be set individually for debounced or direct input

• Each bit can be set individually for pull-up or not

• Each bit is an interrupt request source on the rising or falling edge

• A system reset can be generated on an input pattern

• PA[0] and PA[1] can generate two events for the CPU, individually maskable

• PA[0] to PA[3] can be used as clock inputs for the counters/timers/PWM (product dependent)

• PA[0] can be used to enable the RC oscillator

11.2 Overview

Port A is a general purpose 8 bit wide digital input port, with interrupt capability. Figure 11-1 shows its structure.

Figure 11-1:structure of Port A

VBat

resetfromporta

RegPAPullup

RegPADebounce

RegPAIn

RegPACtrl

RegPAEdge

RegPARes1

RegPARes0

interrupts

events

cntclocks

debounce

DebFast

(RegSysMisc(2)) 256 Hz

8 kHz

Port A

PAReset[x]

11-3

XE8805/05A

11.3 Register map

There are six registers in the Port A (PA), namely RegPAIn, RegPADebounce, RegPAEdge, RegPAPullup,

RegPARes0 and RegPARes1. Table 11-1 to Table 11-6 show the mapping of control bits and functionality.

pos. RegPAIn rw reset description

7:0 PAIn[7:0] r pad PA[7] to PA[0] input value

Table 11-1: RegPAIn

pos. RegPADebounce rw reset description

7:0 PADebounce[7:0] r w 00000000

resetpconf

PA[7] to PA[0]

1: debounce enabled

0: debounce disabled

Table 11-2: RegPADebounce

pos. RegPAEdge rw reset description

7:0 PAEdge[7:0] r w

00000000

resetsystem

PA[7] to PA[0] edge configuration

0: positive edge

1: negative edge

Table 11-3: RegPAEdge

pos. RegPAPullup rw reset description

7:0 PAPullup[7:0] r w

00000000

resetpconf

PA[7] to PA[0] pullup enable

0: pullup disabled

1: pullup enabled

Table 11-4: RegPAPullup

pos. RegPARes0 rw Reset description

7:0 PARes0[7:0] r w

00000000

resetsystem PA[7] to PA[0] reset configuration

Table 11-5: RegPARes0

pos. RegPARes1 rw reset Description

7:0 PARes1[7:0] r w 00000000

resetsystem PA[7] to PA[0] reset configuration

Table 11-6: RegPARes

11.4 Interrupts and events map

Interrupt source Default mapping in

the interrupt manager Default mapping in the

event manager

pa_irqbus[5] RegIrqMid[5]

pa_irqbus[4] RegIrqMid[4]

pa_irqbus[1] RegIrqMid[1] RegEvn[4]

pa_irqbus[0] RegIrqMid[0] RegEvn[0]

pa_irqbus[7] RegIrqLow[7]

pa_irqbus[6] RegIrqLow[6]

pa_irqbus[3] RegIrqLow[3]

pa_irqbus[2] RegIrqLow[2]

11-4

XE8805/05A

11.5 Port A (PA) Operation

The Port A input status (debounced or not) can be read from RegPAin.

Debounce mode:

Each bit in Port A can be individually debounced by setting the corresponding bit in RegPADebounce. After reset,

the debounce function is disabled. After enabling the debouncer, the change of the input value is accepted only if

the input value is identical at two consecutive sampling on the rising edge of the selected clock. Selection of the

clock is done by the bit DebFast in Register RegSysMisc (see clock block documentation for more precision on

the frequency).

DebFast Clock filter

0 256 Hz

1 8 kHz

Table 11-7: debounce frequency selection

Figure 11-2: digital debouncer

Pull-ups:

When the corresponding bit in RegPAPullup is set to 0, the inputs are floating (pull-up resistors are disconnected).

When the corresponding bit in RegPAPullup is set to 1, a pull-up resistor is connected to the input pin. Port A

starts up with the pull-up resistors disconnected.

Port A as an interrupt source:

Each Port A input is an interrupt request source and can be set on rising or falling edge with the corresponding bit

in RegPAEdge. After reset, the rising edge is selected for interrupt generation by default. The interrupt source can

be debounced by setting register RegPADebounce.

Note: care must be taken when modifying RegPAEdge because this register performs an edge selection. The

change of this register may result in a transition which may be interpreted as a valid interruption.

Port A as an event source:

The interrupt signals of the pins PA[0] and PA[1] are also available as events on the event controller.

Port A as a clock source (product dependent):

Images of the PA[0] to PA[3] input ports (debounced or not) are available as clock sources for the

counter/timer/PWM peripheral (see the counter block documentation for more information).

Port A as a reset source:

Port A can be used to generate a system reset by placing a predetermined word on Port A externally. The reset is

built using a logical and of the 8 PARes[x] signals:

resetfromportA = PAReset[7] AND PAReset[6] AND PAReset[5] AND ... AND PAReset[0]

PAReset[x] is itself a logical function of the corresponding pin PA[x]. One of four logical functions can be selected

for each pin by writing into two registers RegPARes0 and RegPARes1 as shown in Table 11-8.

Input

CkDebounce

Debounced 112112

11-5

XE8805/05A

PARes1[x] PARes0[x] PAReset[x]

0 0 0

0 1 PA[x]

1 0 not(PA[x])

1 1 1

Table 11-8: Selection bits for reset signal

A reset from Port A can be inhibited by placing a 0 on both PARes1[x] and PARes0[x] for at least 1 pin. Setting

both PARes1[x] and PARes0[x] to 1, makes the reset independent of t he value on the corresponding pin. Setting

both registers to hFF, will reset the circuit independent from the Port A input value. This makes it possible to do a

software reset.

Note: depending of the value of PA[0] to PA[7], the change of RegPARes0 and RegPARes1 can cause a reset.

Therefore it is safe to have always one (RegPARes0[x], RegPARes1[x]) equal to ‘00’ during the setting operations.

Port A as a RC enable:

PA[0] can be used to enable the RC oscillator. When RCOnPA0 bit in RegSysMisc is set to 1 and the value of

PA[0] (debounced or not) is equal to 1, the EnRc bit in RegSysClock is automatically set to 1.

11.6 Port A electrical specification

Sym description min typ max unit Comments

VINH Input high voltage 0.7*VBAT VBAT V VBAT≥2.4V

VINL Input low voltage VSS 0.2*VBAT V VBAT≥2.4V

RPU Pull-up resistance 20 50 80 kΩ

Cin Input capacitance 3.5 pF Note 1

Note 1: this value is indicative only since it depends on the package.

Table 11-9. Port A electrical specification.

12-1

XE8805/05A

12 Port B

12.1 Features 12-2

12.2 Overview 12-2

12.3 Register map 12-2

12.4 Port B capabilities 12-3

12.5 Port B analog capability 12-3

12.5.1 Port B analog configuration 12-3

12.5.2 Port B analog function specification 12-4

12.6 Port B function capability 12-4

12.7 Port B digital capabilities 12-5

12.7.1 Port B digital configuration 12-5

12.7.2 Port B digital function specification 12-6

12-2

XE8805/05A

12.1 Features

• Input / output / analog port, 8 bits wide

• Each bit can be set individually for input or output

• Each bit can be set individually for open-drain or push-pull

• Each bit can be set individually for pull-up or not (for input or open-drain mode)

• In open-drain mode, pull-up is not active when corresponding pad is set to zero

• The 8 pads can be connected by pairs to four internal analog lines (4 line analog bus)

• Two internal freq. (cpuck and 32 kHz) can be output on PB[2] and PB[3]

Product dependant:

• Two PWM signal can be output on pads PB[0] and PB[1]

• The synchronous serial interface (USRT) uses pads PB[5], PB[4]

• The UART interface uses pads PB[6] and PB[7] for Tx and Rx

12.2 Overview

Port B is a multi-purpose 8 bit Input/output port. In addition to digital functions, all pins can be used for analog

signals. All port terminals can be selected by pairs as digital input or output or as analog to share one of four

possible analog lines.

12.3 Register map

Pos. RegPBOut rw reset description in digital mode description in analog mode

7 – 0 PBOut[7-0] r w 0 resetpconf Pad PB[7-0] output value Analog bus selection for pad PB[7-0]

Table 12-1: RegPBOut

Pos. RegPBIn rw reset description in digital mo d e description in analog mo d e

7 – 0 PBIn[7-0] r w Pad PB[7-0] input status Unused

Table 12-2: RegPBIn

Pos. RegPBDir rw reset description in digital mode description in analog mode

7 – 0 PBDir [7-0] r w 0 resetpconf Pad PB[7-0] direction (0=input) Analog bus selection for pad PB[7-0]

Table 12-3: RegPBDir

Pos. RegPBOpen rw reset descriptio n in digital mode description in analog mode

7 – 0 PBOpen[7-0] r w 0 resetpconf Pad PB[7-0] open drain (1 = open

drain) Unused

Table 12-4: RegPBOpen

Pos. RegPBPullup rw reset descriptio n in d i g i tal mo d e description in analog mo d e

7 –0 PBPullup[7] r w 0 resetpconf Pull-up for pad PB[7-0] (1=active) Connect pad PB[7-0] on selected ana

bus

Table 12-5: RegPBPullup

Pos. RegPBAna rw reset description in d i g i tal mo d e description in analog mo d e

7 – 4 -- r 0000 Unused Unused

3 PBAna [3] r w 0 resetpconf Set PB[7:6] in analog mode Set PB[7:6] in analog mode

2 PBAna [2] r w 0 resetpconf Set PB[5:4] in analog mode Set PB[5:4] in analog mode

1 PBAna [1] r w 0 resetpconf Set PB[3:2] in analog mode Set PB[3:2] in analog mode

0 PBAna [0] r w 0 resetpconf Set PB[1:0] in analog mode Set PB[1:0] in analog mode

Table 12-6: RegPBAna

12-3

XE8805/05A

Note: Depending on the status of the EnResPConf bit in RegSysCtrl, the reset conditions of the registers are

different. See the reset block documentation for more details on the resetpconf signal.

12.4 Port B capabilities

Port B usage (priority)

name analog

(high) functions

(medium) digital

(low) (default)

PB[7] uart Rx I/O

PB[6] analog uart Tx I/O

PB[5] usrt S1 I/O

PB[4] analog usrt S0 I/O

PB[3] 32 kHz I/O

PB[2] analog clock CPU I/O

PB[1] PWM1 Counter C (C+D) I/O

PB[0] analog PWM0 Counter A (A+B) I/O

Table 12-7: Different Port B functionality

Table 12-7 shows the different usage that can be made of the port B with the order of priority. If a pair of pins is

selected to be analog, it overwrites the function and digital set-up. If the pin is not selected as analog, but a

function is enabled, it overwrites the digital set-up. If neither the analog nor function are selected for a pin, it is used

as an ordinary digital I/O. This is the default configuration at start-up.

12.5 Port B analog capability

12.5.1 Port B analog configuration

Port B terminals can be attached to a 4 line analog bus by setting the PBAna[x] bits to 1 in the RegPBAna

The other registers then define the connection of these 4 analog lines to the different pads of Port B. This can be

used to implement a simple LCD driver or A/D converter. Analog switching is available only when the circuit is

powered with sufficient voltage (see specification below). Below the specified supply voltage, only voltages that are

close to VSS or VBAT can be switched.

When PBAna[x] is set to 1, a pair of Port B terminals is switched from digital I/O mode to analog mode. The usage

of the registers RegPBPullup, RegPBOut and RegPBDir define the analog configuration (see Table 12-8).

When PBAna[x] = 1, then PBPullup[x] connects the pin to the analog bus. PBDir[x] and PBPOut[x] select which

of the 4 analog lines is used. For odd values of x, the selection bits are in the register RegPBOut (see Table 12-8).

For even values of x, the selection bits are in the register RegPBDir (see Table 12-9).

if x is odd, PBOut[x, x-1] PBPullup[x] PB[x] selection on

00 1 analog line 0

01 1 analog line 1

10 1 analog line 2

11 1 analog line 3

XX 0 High impedance

Table 12-8: Selection of the analog lines for PB[x] when x is odd and PBAna[x] = 1

12-4

XE8805/05A

if x is even, PBDir[x+1, x] PBPullup[x] PB[x] selection on

00 1 analog line 0

01 1 analog line 1

10 1 analog line 2

11 1 analog line 3

XX 0 High impedance

Table 12-9: Selection of the analog lines for PB[x] when x is even and PBAna[x] = 1

Example:

Set the pads PB[2] and PB[3] on the analog line 3. (the values X depend on the configuration of others

pads)

- apply high impedance in the analog mode (move RegPBPullup,#0bXXXX00XX)

- go to analog mode (move RegPBAna,#0bXXXXXX1X)

- select the analog line3 (move RegPBDir,#0bXXXX11XX and move RegPBOut,#0bXXXX11XX)

- connect the analog line to the pins (move RegPBPullup,#0bXXXX11XX)

12.5.2 Port B analog function specification

The table below defines the on-resistance of the switches between the pin and the analog bus for different

conditions. The series resistance between 2 pins of Port B connected to the same analog line is twice the

resistance given in the table.

sym description min typ max unit Comments

Ron switch resistance 11 kΩ Note 1

Ron switch resistance 15 kΩ Note 2

Cin input capacitance (off) 3.5 pF Note 3

Cin input capacitance (on) 4.5 pF Note 4

Table 12-10. Analog input specifications.

Note 1: This is the series resistance between the pad and the analog line in 2 cases

1. VBAT ≥ 2.4V and the VMULT peripheral is present on the circuit and enabled.

2. VBAT ≥ 3.0V and the VMULT peripheral is not present on the circuit.

Note 2: This is the series resistance in case VBAT ≥ 2.8V and the peripheral VMULT is not present on the circuit.

Note 3: This is the input capacitance seen on the pin when the pin is not connected to an analog line. This value is

indicative only since it is product and package dependent.

Note 4: This is the input capacitance seen on the pin when the pin is connected to an analog line and no other pin

is connected to the same analog line. This value is indicative only since it is product and package dependent.

12.6 Port B function capability

The Port B can be used for different functions implemented by other peripherals. The description below is

applicable only in so far the circuit contains these peripherals.

When the counters are used to implement a PWM function (see the documentation of the counters), the PB[0] and

PB[1] terminals are used as outputs (PB[0] is used if CntPWM0 in RegCntConfig1 is set to 1, PB[1] is used if

CntPWM1 in RegCntConfig1 is set to 1) and the PWM generated values overwrite the values written in

RegPBout. However, PBDir(0) and PBDir(1) are not automatically overwritten and have to be set to 1.

If OutputCkXtal is set in RegSysMisc, the Xtal clock is output on PB[3] (EnableXtal in RegSysClock must be set

to 1). This overrides the value contained in PBOut(3). However, PBDir(3) must be set to 1. The duty cycle of the

clock signal is about 50%.

Similarly, if OutputCkCpu is set in RegSysMisc, the CPU frequency is output on PB[2]. This overrides the value

contained in PBOut(2). However, PBDir(2) must be set to 1.

12-5

XE8805/05A

The frequency of the CPU clock depends on the selection of the CpuSel bit in the RegSysClock register (see

clock_gen_ff).

Pins PB[5] and PB[4] can be used for S1 and S0 of the USRT (see USRT documentation) when the UsrtEnable bit

is set in RegUsrtCtrl. The PB[5] and PB[4] then become open-drain. This overrides the values contained in

PBOpen(5:4), PBOut(5:4) and PBDir(5:4). If there is no external pull-up resistor on these pins, internal pull-ups

should be selected by setting PBPullup(5:4). When S0 is an output, the pin PB[4] takes the value of UsrtS0 in

RegUrstS0. When S1 is an output, the pin PB[5] takes the value of UsrtS1 in RegUrstS1.

Pins PB[6] and PB[7] can be used by the UART (see UART documentation). When UartEnTx in RegUartCtrl is set

to 1, PB[6] is used as output signal Tx. When UartEnRx in RegUartCtrl is set to 1, PB[7] is used as input signal

Rx. This overrides the values contained in PBOut(7:6) and PBDir(7:6).

12.7 Port B digital capabilities

12.7.1 Port B digital configuration

The direction of each bit within Port B (input only or input/output) can be individually set using the RegPBDir

the corresponding Port B pin is an input only and the output buffer is in high impedance. After reset (resetpconf)

Port B is in input only mode (PBDir[x] are reset to 0).

The input values of Port B are available in RegPBIn (read only). Reading is always direct - there is no debounce

function in Port B. In case of possible noise on input signals, a software debouncer with polling or an external

hardware filter have to be realized. The input buffer is also active when the port is defined as output and allows to

read back the effective value on the pin.

Data stored in RegPBOut are output at Port B if PBDir[x] is 1. The default value after reset is low (0).

When a pin is in output mode (PBDir[x] is set to 1), the output can be a conventional CMOS (Push-Pull) or a N-

channel Open-drain, driving the output only low. By default, after reset (resetpconf) the PBOpen[x] in RegPBOpen

is cleared to 0 (push-pull). If PBOpen[x] in RegPBOpen is set to 1 then the internal P transistor in the output buffer

is electrically removed and the output can only be driven low (PBOut[x]=0). When PBOut[x]=1, the pin is high

Impedance. The internal pull-up or an external pull-up resistor can be used to drive the pin high.

Note: Because the P transistor actually exists (this is not a real Open-drain output) the pull-up range is limited to

VDD + 0.2V (avoid forward bias the P transistor / diode).

Each bit can be set individually for pull-up or not using register RegPBPullup. Input is pulled up when its

corresponding bit in this register is set to 1. Default status after (resetpconf) is 0, which means without pull up. To

limit power consumption, pull-up resistors are only enabled when the associated pin is either a digital input or an N-

channel open-drain output with the pad set to 1. In the other cases (push-pull output or open-drain output driven

low), the pull up resistors are disabled independent of the value in RegPBPullup.

After power-on reset, the Port B is configured as an input port without pull-up.

The input buffer is always active, except in analog mode. This means that the Port B input should be a valid digital

value at all times unless the pin is set in analog mode. Violating this rule may lead to higher power consumption.

12-6

XE8805/05A

12.7.2 Port B digital function specification

Sym description min typ max unit Comments

VINH Input high voltage 0.7*VBAT VBAT V VBAT≥2.4V

VINL Input low voltage VSS 0.2*VBAT V VBAT≥2.4V

VOH Output high voltage VBAT-0.4

VBAT V VBAT=1.2V, IOH =0.3mA

VBAT=2.4V, IOH =5.0mA

VBAT=4.5V, IOH =8.0mA

VOL Output low voltage VSS

VSS+0.4 V VBAT=1.2V, IOL =0.3mA

VBAT=2.4V, IOL

=12.0mA

VBAT=4.5V, IOL

=15.0mA

RPU Pull-up resistance 20 50 80 kΩ

Cin Input capacitance 3.5 pF Note 1

Note 1: this value is indicative only since it depends on the package.

13-1

XE8805/05A

13 Port C

13.1 Features 13-2

13.2 Overview 13-2

13.3 Port C (PC) Operation 13-2

13.4 Register map 13-2

13.5 Port C electrical specification 13-3

13-2

XE8805/05A

13.1 Features

• Input / output port, 8 bits wide

• Each bit can be set individually for input or output

13.2 Overview

Port C (PC) is a general purpose 8 bit input/output digital port.

Figure 13-1 shows its structure.

Figure 13-1: structure of Port C

13.3 Port C (PC) Operation

The direction of each bit within Port C (input or output) can be individually set by using the RegPCDir register. If

PCDir[x] = 1, the corresponding Port C pin becomes an output. After reset, Port C is in input mode (PCDir[x] are

reset to 0).

Output mode:

Data is stored in RegPCOut prior to output at Port C.

Input mode:

The status of Port C is available in RegPCIn (read only). Reading is always direct - there is no digital debounce

function associated with Port C. In case of possible noise on input signals, a software debouncer or an external

filter must be realized.

By default after reset, Port C is configured as an input port.

13.4 Register map

There are three registers in the Port C (PC), namely RegPCIn, RegPCOut and RegPCDir. Table 13-1 to Table

13-3 show the mapping of control bits and functionality of these registers.

Pos. RegPCIn Rw Reset Description

7-0 PCIn r - pad PC input value

Table 13-1. RegPCIn

RegPCIn

RegPCOut

RegPCDir

Port C

13-3

XE8805/05A

Pos. RegPCOut Rw Reset Description

7-0 PCOut r w 0 resetpconf pad PC output value

Table 13-2. RegPCOut

Pos. RegPCDir Rw Reset Description

7-0 PCDir r w 0 resetpconf pad PC direction (0=input)

Table 13-3. RegPCDir

13.5 Port C electrical specification

Sym description min typ max unit Comments

VINH Input high voltage 0.7*VBAT VBAT V VBAT≥2.4V

VINL Input low voltage VSS 0.2*VBAT V VBAT≥2.4V

VOH Output high voltage VBAT-0.4

VBAT V VBAT=1.2V, IOH =0.3mA

VBAT=2.4V, IOH =5.0mA

VBAT=4.5V, IOH =8.0mA

VOL Output low voltage VSS

VSS+0.4 V VBAT=1.2V, IOL =0.3mA

VBAT=2.4V, IOL

=12.0mA

VBAT=4.5V, IOL

=15.0mA

Cin Input capacitance 3.0 pF Note 1

Note 1: this value is indicative only since it depends on the package.

Table 13-4. Port C electrical specification

14-1

XE8805/05A

14 UART

14.1 Features 14-2

14.2 Overview 14-2

14.3 Registers map 14-2

14.4 Interrupts map 14-3

14.5 Uart baud rate selection 14-3

14.5.1 Uart on the RC oscillator 14-3

14.5.2 Uart on the crystal oscillator 14-4

14.6 Function description 14-4

14.6.1 Configuration bits 14-4

14.6.2 Transmission 14-5

14.6.3 Reception 14-5

14.7 Interrupt or polling 14-6

14.8 Software hints 14-7

14-2

XE8805/05A

14.1 Features

• Full duplex operation with buffered receiver and transmitter.

• Internal baud rate generator with 12 programmable baud rates (300 - 115200).

• 7 or 8 bits word length.

• Even, odd, or no-parity bit generation and detection

• 1 stop bit

• Error receive detection: Start, Parity, Frame and Overrun

• Receiver echo mode

• 2 interrupts (receive full and transmit empty)

• Enable receive and/or transmit

• Invert pad Rx and/or Tx

14.2 Overview

The UART pins are PB[7], which is used as Rx - receive and PB[6] as Tx - transmit.

14.3 Registers map

pos. RegUartCmd rw Reset Description

7 SelXtal rw 0 resetsystem Select input clock: 0 = RC, 1 = xtal

6 UartEnRx2 rw 0 resetsystem Enable Uart Reception

5-3 UartRcSel(2:0) rw 000 resetsystem RC prescaler selection

2 UartPM rw 0 resetsystem Select parity mode: 0 = odd, 1 = even

1 UartPE rw 0 resetsystem Enable parity: 1 = with parity, 0 = no parity

0 UartWL rw 1 resetsystem Select word length: 1 = 8 bits, 0 = 7 bits

Table 14-1: RegUartCmd

Pos. RegUartCtrl rw reset Description

7 UartEcho rw 0 resetsystem Enable echo mode:

1 = echo Rx->Tx, 0 = no echo

6 UartEnRx1 rw 0 resetsystem Enable uart reception

5 UartEnTx rw 0 resetsystem Enable uart transmission

4 UartXRx rw 0 resetsystem Invert pad Rx

3 UartXTx rw 0 resetsystem Invert pad Tx

2-0 UartBR(2:0) rw 101 resetsystem Select baud rate

Table 14-2: RegUartCtrl

pos. RegUartTx rw reset Description

7-0 UartTx rw 00000000

resetsystem Data to be sent

Table 14-3: RegUartTx

14-3

XE8805/05A

pos. RegUartTxSta rw reset description

7-2 - r 000000 Unused

1 UartTxBusy r 0 resetsystem Uart busy transmitting

0 UartTxFull r 0 resetsystem RegUartTx full

Set by writing to RegUartTx

Cleared when transferring RegUartTx into

internal shift register

Table 14-4: RegUartTxSta

pos. RegUartRx rw reset description

7-0 UartRx r 00000000

resetsystem Received data

Table 14-5: RegUartRx

pos. RegUartRxSta rw Reset description

7-6 - r 00 Unused

5 UartRxSErr r 0 resetsystem Start error

4 UartRxPErr r 0 resetsystem Parity error

3 UartRxFErr r 0 resetsystem Frame error

2 UartRxOErr rc 0 resetsystem Overrun error

Cleared by writing RegUartRxSta

1 UartRxBusy r 0 resetsystem Uart busy receiving

0 UartRxFull r 0 resetsystem RegUartRx full

Cleared by reading RegUartRx

Table 14-6: RegUartRxSta

14.4 Interrupts map

interrupt source default mapping in the interrupt manager

Irq_uart_Tx IrqHig(1)

Irq_uart_Rx IrqHig(0)

Table 14-7: Interrupts map

14.5 Uart baud rate selection

In order to have correct baud rates, the Uart interface has to be fed with a stable and trimmed clock source. The

clock source can be the RC oscillator or the crystal oscillator. The precision of the baud rate will depend on the

precision of the selected clock source.

14.5.1 Uart on the RC oscillator

To select the RC oscillator for the Uart, the bit SelXtal in RegUartCmd has to be 0.

In order to obtain a correct baud rate, the RC oscillator frequency has to be set to one of the frequencies given in

the table on the next page. The precision of the obtained baud rate is directly proportional to the frequency

deviation with respect to the values in the table.

14-4

XE8805/05A

Frequency selection for correct Uart

baud rate with RC oscillator (Hz)

2’457’600

1’843’200

1’228’800

614’400

For each of these frequencies, the baud rate can be selected with the bits UartBR(2:0) in RegUartCtrl and

UartRcSel(2:0) in RegUartCmd as shown in Table 14-8

RC frequency (Hz) 2’457’600 1’228’800 614’400 1’843’200

UartRcSel 010 001 000 000

111 38400 115200

110 19200 57600

101 9600 28800

UartBR

100 Not possible 4800 14400

Table 14-8: Uart baud rate with RC clock

Note: The precision of the baud rate is directly proportional to the frequency deviation of the used clock from the

ideal frequency given in the table. In order to increase the precision and stability of the RC oscillator, the DFLL

(digital frequency locked loop) can be used with the crystal oscillator as a reference.

14.5.2 Uart on the crystal oscillator

In order to use the crystal oscillator as the clock source for the Uart, the bit SelXtal in RegUartCmd has to be set.

The crystal oscillator has to be enabled by setting the EnableXtal bit in RegSysClock. The baud rate selection is

done using the UartBR and UartRcSel bits as shown in Table 14-9.

Xtal freq. (Hz) UartRcSel UartBR Baud rate

011 2400

010 1200

001 600

32768 001

000 300

Table 14-9: Uart baud rate with Xtal clock

Due to the odd ratio between the crystal oscillator frequency and the baud rate, the generated baud rate has a

systematic error of –2.48%.

14.6 Function description

14.6.1 Configuration bits

The configuration bits of the Uart serial interface can be found in the registers RegUartCmd and RegUartCtrl.

The bit SelXtal is used to select the clock source (see chapter 14.5). The bits UartSelRc and UartBR select the

baud rate (see chapter 14.5).

The bits UartEnTx is used to enable or disable the transmission.

The bits UartEnRx1 and UartEnRx2 are used to enable or disable the reception. When one is set to 1, the

reception is enabled.

14-5

XE8805/05A

The word length (7 or 8 data bits) can be chosen with UartWL. A parity bit is added during transmission or checked

during reception if UartPE is set. The parity mode (odd or even) can be chosen with UartPM.

Setting the bits UartXRx and UartXTx inverts the Rx respectively Tx signals.

The bit UartEcho is used to send the received data automatically back. The transmission function becomes then:

Tx = Rx XOR UartXTx.

14.6.2 Transmission

In order to send data, the transmitter has to be enabled by setting the bit UartEnTx. Data to be sent has to be

written to the register RegUartTx. The bit UartTxFull in RegUartTxSta then goes to 1, indicating to the transmitter

that a new word is available. As soon as the transmitter has finished sending the previous word, it then loads the

contents of the register RegUartTx to an internal shift register and clears the UartTxFull bit. An interrupt is

generated on Irq_uart_Tx at the falling edge of the UartTxFull bit. The bit UartTxBusy in RegUartTxSta shows

that the transmitter is busy transmitting a word.

A timing diagram is shown in Figure 14-1. Data are first sent LSB.

New data should be written to the register RegUartTx only while UartTxFull is 0, otherwise data will be lost.

Asynchronous Transm ission

write to Re

UartTx

UartTx word 1

reguarttx_shift word 1

shift clock

Tx start b0 b1 b6/7 parity stop

UartTxBus

UartTxFull

Irq_uart_Tx

Asynchronous T ransmission (back to back)

word 1 word 2

write to Re

UartTx

UartTx word 1 word 2

reguarttx_shift word 1 word 2

shift clock

Tx start b0 b6/7 stop start

UartTxBus

UartTxFull

Irq_uart_Tx

Figure 14-1. Uart transmission timing diagram.

14.6.3 Reception

On detection of the start bit, the UartRxBusy bit is set. On detection of the stop bit, the received data are

transferred from the internal shift register to the register RegUartRx. At the same time, the UartRxFull bit is set

14-6

XE8805/05A

and an interrupt is generated on Irq_uart_Rx. This indicates that new data is available in RegUartRx. The timing

diagram is shown in Figure 14-2.

The UartRxFull bit is cleared when RegUartRx is read. If the register was not read before the receiver transfers a

new word to it, the bit UartRxOErr (overflow error) is set and the previous contents of the register is lost.

UartRxOErr is cleared by writing any data to RegUartRxSta.

The bit UartRxSErr is set if a start error has been detected. The bit is updated at data transfer to RegUartRx.

The bit UartRxPErr is set if a parity error has been detected, i.e. the received parity bit is not equal to the

calculated parity of the received data. The bit is updated at data transfer to RegUartRx.

The bit UartRxFErr in RegUartRxSta shows that a frame error has been detected. No stop bit has been detected.

Asynchronous Reception

read of RegU artRx (software)

reguartrx_shift word 1

RegUartRx word 1

shift clock

Rx start b0 b6/7 parity stop

UartRxBusy

UartRxFull

Irq_uart_Rx

Figure 14-2. Uart reception timing diagram.

14.7 Interrupt or polling

The transmission and reception software can be driven by interruption or by polling the status bits.

Interrupt driven reception: each time an Irq_uart_Rx interrupt is generated, a new word is available in RegUartRx.

The register has to be read before a new word is received.

Interrupt driven transmission: each time the contents of RegUartTx is transferred to the transmission shift register,

an Irq_uart_Tx interrupt is generated. A new word can then be written to RegUartTx.

Reception driven by polling: the UartRxFull bit is to be read and checked. When it is 1, the RegUartRx register

contains new data and has to be read before a new word is received.

Transmission driven by polling: the UartTxFull bit is to read and checked. When it is 0, the RegUartTx register is

empty and a new word can be written to it.

14-7

XE8805/05A

14.8 Software hints

Example of program for a transmission with polling:

1. The RegUartCmd register and the RegUartCtrl register are initialized (for example: 8 bit word length, odd

parity, 9600 baud, enable Uart transmission).

2. Write a byte to RegUartTx.

3. Wait until the UartTxFull bit in RegUartTxSta register equals 0.

4. Jump to 2 to write the next byte if the message is not finished.

5. End of transmission.

Example of program for a transmission with interrupt:

1. The RegUartCmd register and the RegUartCtrl register are initialized (for example: 8 bit word length, odd

parity, 9600 baud, enable Uart transmission).

2. Write a byte to RegUartTx.

3. After an interrupt and if the message is not finished, jump to 2

4. End of transmission.

Example of program for a reception with polling:

1. The RegUartCmd register and the RegUartCtrl register are initialized (for example: 8 bit word length, odd

parity, 9600 baud, enable Uart reception).

2. Wait until the UartRxFull bit in the RegUartRxSta register equals 1.

3. Read the RegUartRxSta and check if there is no error.

4. Read data in RegUartRx.

5. If data is not equal to End-Of-Line, then jump to 2.

6. End of reception.

Example of program for a reception with interrupt:

1. The RegUartCmd register and the RegUartCtrl register are initialized (for example: 8 bit word length, odd

parity, 9600 baud, enable Uart reception).

2. When there is an interrupt, jump to 3

3. Read RegUartRxSta and check if there is no error.

4. Read data in RegUartRx.

5. If data is not equal to End-Of-Line, then jump to 2.

6. End of reception.

15-1

XE8805/05A

15 USRT

15.1 Features 15-2

15.2 Overview 15-2

15.3 Register map 15-2

15.4 Interrupts map 15-4

15.5 Conditional edge detection 1 15-4

15.6 Conditional edge detection 2 15-4

15.7 Interrupts or polling 15-5

15.8 Function description 15-5

15-2

XE8805/05A

15.1 Features

The USRT implements a hardware support for software implemented serial protocols:

• Control of two external lines S0 and S1 (read/write).

• Conditional edge detection generates interrupts.

• S0 rising edge detection.

• S1 value is stored on S0 rising edge.

• S0 signal can be forced to 0 after a falling edge on S0 for clock stretching in the low state.

• S0 signal can be stretched in the low state after a falling edge on S0 and after a S1 conditional detection.

15.2 Overview

The USRT block supports software universal synchronous receiver and transmitter mode interfaces.

External lines S0 and S1 respectively correspond to clock line and data line. S0 is mapped to PB[4] and S1 to

PB[5] when the USRT block is enabled. It is independent from RegPBdir (Port B can be input or output). When

USRT is enabled, the configurations in port B for PB[4] and PB[5] are overwritten by the USRT configuration.

Internal pull-ups can be used by setting the PBPullup[5:4] bits.

Conditional edge detections are provided.

RegUsrtS1 can be used to read the S1 data line from PB[5] in receive mode or to drive the output S1 line PB[5] by

writing it when in transmit mode. It is advised to read S1 data when in receive mode from the RegUsrtBufferS1

15.3 Register map

Block configuration registers:

pos. RegUsrtS1 rw reset function

7-1 - r 0000000 Unused

0 UsrtS1 rw 1 resetsystem Write: data S1 written to pad PB[5]),

Read: value on PB[5] (not UsrtS1 value).

Table 15-1: RegUsrtS1

pos. RegUsrtS0 rw Reset function

7-1 - r 0000000 Unused

0 UsrtS0 rw 1 resetsystem Write: clock S0 written to pad PB[4],

Read: value on PB[4] (not UsrtS0 value).

Table 15-2: RegUsrtS0

The values that are read in the registers RegUsrtS1 and RegUsrtS0 are not necessarily the same as the values

that were written in the register. The read value is read back on the circuit pins, not in the registers. Since the

outputs are open drain, a value different from the register value may be forced by an external circuit on the circuit

pins.

15-3

XE8805/05A

pos. RegUsrtCtrl rw reset function

7-4 - r “0000” Unused

3 UsrtWaitS0 r 0 resetsystem Clock stretching flag (0=no stretching),

cleared by writing RegUsrtBufferS1

2 UsrtEnWaitCond1 rw 0 resetsystem Enable stretching on UsrtCond1 detection

(0=disable)

1 UsrtEnWaitS0 rw 0 resetsystem Enable stretching operation (0=disable)

0 UsrtEnable rw 0 resetsystem Enable USRT operation (0=disable)

Table 15-3: RegUsrtCtrl

pos. RegUsrtCond1 rw reset function

7-1 - r 0000000 Unused

0 UsrtCond1 r/c 0 resetsystem State of condition 1 detection (1 =detected),

cleared when written.

Table 15-4: RegUsrtCond1

pos. RegUsrtCond2 rw reset function

7-1 - r 0000000 Unused

0 UsrtCond2 r/c 0 resetsystem State of condition 2 detection (1 =detected),

cleared when written.

Table 15-5: RegUsrtCond2

pos. RegUsrtBufferS1 rw reset function

7-1 - r 0000000 Unused

r Value on S1 at last S0 rising edge.

Clear RegUsrtEdgeS0 bit in RegUsrtEdgeS0

0 UsrtBufferS1 w x Clear UsrtWaitS0 bit in RegUsrtCtrl with any

value

Table 15-6: RegUsrtBufferS1

15-4

XE8805/05A

pos. RegUsrtEdgeS0 rw reset function

7-1 - r 0000000 Unused

0 UsrtEdgeS0 r 0 resetsystem State of rising edge detection on S0

(1=detected). Cleared by reading

RegUsrtBufferS1

Table 15-7: RegUsrtEdgeS0

15.4 Interrupts map

interrupt

source default mapping in the interrupt manager

Irq_cond1 RegIrqMid(7)

Irq_cond2 RegIrqMid(6)

Table 15-8: Interrupts map

15.5 Conditional edge detection 1

Figure 15-1: Condition 1

Condition 1 is satisfied when S0=1 at the falling edge of S1. The bit UsrtCond1 in RegUsrtCond1 is set when the

condition 1 is detected and the USRT interface is enabled (UsrtEnable=1). Condition 1 is asserted for both modes

(receiver and transmitter). The UsrtCond1 bit is read only and is cleared by all reset conditions and by writing any

data to its address.

Condition 1 occurrence also generates an interrupt on Irq_cond1.

15.6 Conditional edge detection 2

Figure 15-2: Condition 2

15-5

XE8805/05A

Condition 2 is satisfied when S0=1 at the rising edge of S1. The bit UsrtCond2 in RegUsrtCond2 is set when the

condition 2 is detected and the USRT interface is enabled. Condition 2 is asserted for both modes (receiver and

transmitter). The UsrtCond2 bit is read only and is cleared by all reset conditions and by writing any data to its

address.

Condition 2 occurrence also generates an interrupt on Irq_cond2.

15.7 Interrupts or polling

In receive mode, there are two possibilities for detecting condition 1 or 2: the detection of the condition can

generate an interrupt or the registers can be polled (reading and checking the RegUsrtCond1 and RegUsrtCond2

registers for the status of USRT communication).

15.8 Function description

The bit UsrtEnable in RegUsrtCtrl is used to enable the USRT interface and controls the PB[4] and PB[5] pins.

This bit puts these two port B lines in the open drain configuration requested to use the USRT interface.

If no external pull-ups are added on PB[4] and PB[5], the user can activate internal pull-ups by setting PBPullup[4]

and PBPullup[5] in RegPBPullup.

The bits UsrtEnWaitS0, UsrtEnWaitCond1, UsrtWaitS0 in RegUsrtCtrl are used for transmitter/receiver control

of USRT interface.

Figure 15-3 shows the unconditional clock stretching function which is enabled by setting UsrtEnWaitS0.

UsrtWaitS0

write RegUsrtBufferS1

Figure 15-3: S0 Stretching (UsrtEnWaitS0=1)

When UsrtEnWaitS0 is 1, the S0 line will be maintained at 0 after its falling edge (clock stretching). UsrtWaitS0 is

then set to 1, indicating that the S0 line is forced low. One can release S0 by writing to the RegUsrtBufferS1

The same can be done in combination with condition 1 detection by setting the UsrtEnWaitCond1 bit. Figure 15-4

shows the conditional clock stretching function which is enabled by setting UsrtEnWaitCond1.

15-6

XE8805/05A

UsrtWaitS0

write RegUsrtBufferS1

Figure 15-4: Conditional stretching (UsrtEnWaitCond1=1)

When UsrtEnWaitCond1 is 1, the S0 signal will be stretched in its low state after its falling edge if the condition 1

has been detected before (UsrtCond1=1). UsrtWaitS0 is then set to 1, indicating that the S0 line is forced low.

One can release S0 by writing to the RegUsrtBufferS1 register.

Figure 15-5 shows the sampling function implemented by the UsrtBufferS1 bit. The bit UsrtBufferS1 in

RegUsrtBufferS1 is the value of S1 sampled on PB[4] at the last rising edge of S0. The bit UsrtEdgeS0 in

RegUsrtEdgeS0 is set to one on the same S0 rising edge and is cleared by a read operation of the

RegUsrtBufferS1 register. The bit therefore indicates that a new value is present in the RegUsrtBufferS1 which

has not yet been read.

UsrtB ufferS1

read RegUsrtBufferS1

UsrtEdgeS0

Figure 15-5: S1 sampling

16-1

XE8805/05A

16. Acquisition chain

16.1 ZoomingADC™ Features.......................................................................................................... 16-2

16.2 Overview....................................................................................................................................16-2

16.3 Register map............................................................................................................................. 16-2

16.4 ZoomingADC™ Description.....................................................................................................16-4

16.4.1 Acquisition Chain........................................................................................................................16-4

16.4.2 Peripheral Registers...................................................................................................................16-6

16.4.3 Continuous-Time vs. On-Request..............................................................................................16-8

16.5 Input Multiplexers.....................................................................................................................16-9

16.6 Programmable Gain Amplifiers............................................................................................. 16-10

16.6.1 PGA & ADC Enabling...............................................................................................................16-12

16.6.2 PGA1 ........................................................................................................................................16-12

16.6.3 PGA2 ........................................................................................................................................16-12

16.6.4 PGA3 ........................................................................................................................................16-12

16.7 ADC Characteristics...............................................................................................................16-13

16.7.1 Conversion Sequence .............................................................................................................. 16-13

16.7.2 Sampling Frequency.................................................................................................................16-14

16.7.3 Over-Sampling Ratio ................................................................................................................16-14

16.7.4 Elementary Conversions...........................................................................................................16-14

16.7.5 Resolution.................................................................................................................................16-15

16.7.6 Conversion Time & Throughput................................................................................................16-16

16.7.7 Output Code Format.................................................................................................................16-16

16.7.8 Power Saving Modes................................................................................................................ 16-18

16.8 Specifications and Measured Curves................................................................................... 16-18

16.8.1 Default Settings ........................................................................................................................16-19

16.8.2 Specifications............................................................................................................................16-20

16.8.3 Linearity ....................................................................................................................................16-21

16.8.3.1 Integral non-linearity.................................................................................................................16-21

16.8.3.2 Differential non-linearity............................................................................................................16-25

16.8.4 Noise.........................................................................................................................................16-26

16.8.5 Gain Error and Offset Error.......................................................................................................16-27

16.8.6 Power Consumption ................................................................................................................. 16-28

16.8.7 Power Supply Rejection Ratio..................................................................................................16-30

16.9 Application Hints.................................................................................................................... 16-31

16.9.1 Input Impedance.......................................................................................................................16-31

16.9.2 PGA Settling or Input Channel Modifications ........................................................................... 16-31

16.9.3 PGA Gain & Offset, Linearity and Noise...................................................................................16-31

16.9.4 Frequency Response................................................................................................................16-32

16.9.5 Power Reduction ......................................................................................................................16-33

16-2

XE8805/05A

16.1 ZoomingADC™ Features

The ZoomingADC ™ is a complete and versatile low-power analog front-end interface typically intended for sensing

applications. The key features of the ZoomingADC™ are:

Programmable 6 to 16-bit dynamic rang e oversampled ADC

• Flexible gain programming between 0.5 and 1000

• Flexible and large range of fset compensation

• 4-channel differential or 8-channel single-ended input multiplexer

• 2-channel differential reference inputs

• Power saving modes

• Direct interfacing to CoolRisc™ microcontroller

16.2 Overview

PGA1 PGA2 PGA3

ADC

MUX

GD1 GD2 GD3

OFF2 OFF3

Analog

Inputs

REF

IN,ADC

Gain1 Gain2 Gain3

Offset3Offset2

Reference

Selection

Input

Selection

ZOOM

Reference

Inputs

Figure 16-1. ZoomingADC™ general functional block diagram

The total acquisition chain consists of an input multiplexer, 3 programmable gain amplifier stages and an

oversampled A/D converter. The reference voltage can be selected on two different channels. Two offset

compensation amplifiers allow for a wide offset compensation range. The programmable gain and offset allow one

to zoom in on a small portion of the reference voltage defined input range.

16.3 Register map

There are eight registers in the acquisition chain (AC), namely RegAcOutLsb, RegAcOutMsb, RegAcCfg0,

RegAcCfg1, RegAcCfg2, RegAcCfg3, RegAcCfg4 and RegAcCfg5. Table 16-2 to Table 16-9 show the mapping

of control bits and functionality of these registers while Table 16-1 gives an overview of these eight.

The register map only gives a short description of the different configuration bits. More detailed information is found

in subsequent sections.

16-3

XE8805/05A

RegAcOutLsb

RegAcOutMsb

RegAcCfg0

RegAcCfg1

RegAcCfg2

RegAcCfg3

RegAcCfg4

RegAcCfg5

Table 16-1: AC register s

pos. RegAcOutLsb rw reset description

7:0 Out[7:0] r

00000000

resetsystem LSB of the output code

Table 16-2: RegAcOutLsb

pos. RegAcOutMsb rw reset description

7:0 Out[15:8] r

00000000

resetsystem MSB of the output code

Table 16-3: RegAcOutMsb

pos. RegAcCfg0 rw reset description

7 Start w r0 0 resetsystem starts a conversion

6:5 SET_NELCONV[1:0] r w 01 resetsystem sets the number of elementary conversions

4:2 SET_OSR[2:0] r w 010 resetsystem

sets the oversampling rate of an elementary

conversion

1 CONT r w 0 resetsystem continuous conversion mode

0 reserved r w 0 resetsystem

Table 16-4: RegAcCfg0

pos. RegAcCfg1 rw reset description

7:6 IB_AMP_ADC[1:0] r w 11 resetsystem Bias current selection of the ADC conv erter

5:4 IB_AMP_PGA[1:0] r w 11 resetsystem Bias current selection of the PGA stages

3:0 ENABLE[3:0] r w

0000

resetsystem Enables the different PGA stages and the ADC

Table 16-5: RegAcCfg1

pos. RegAcCfg2 rw reset description

7:6 FIN[1:0] r w 00 resetsystem Sampling frequency selection

5:4 PGA2_GAIN[1:0] r w 00 resetsystem PGA2 stage gain selection

3:0 PGA2_OFFSET[3:0] r w

0000

resetsystem PGA2 stage offset selection

Table 16-6: RegAcCfg2

16-4

XE8805/05A

pos. RegAcCfg3 rw reset description

7 PGA1_GAIN r w 0 resetsystem PGA1 stage gain selection

6:0 PGA3_GAIN[6:0] r w 0000000

resetsystem PGA3 stage gain sel ection

Table 16-7: RegAcCfg3

pos. RegAcCfg4 rw reset description

7 reserved r 0 Unused

6:0 PGA3_OFFSET[6:0] r w 0000000

resetsystem PGA3 stage offset selection

Table 16-8: RegAcCfg4

pos. RegAcCfg5 rw reset description

7 BUSY r 0 resetsystem Activity flag

6 DEF w r0 0 Selects default configuratio n

5:1 AMUX[4:0] r w 00000

resetsystem Input channel configuration selector

0 VMUX r w 0 resetsystem Reference channel selector

Table 16-9: RegAcCfg5

16.4 ZoomingADC™ Description

Figure 16-2 gives a more detailed description of the acqui sition chain.

16.4.1 Acquisition Chain

Figure 16-1 shows the general block diagram of the acquisition chain (AC). A control block (not shown in Figure

16-1) manages all communications with the CoolRisc™ microcontroller.

Analog inputs can be selected among eight input channels, while reference input is selected between two

differential channels.

The core of the zooming section is made of three differential programmable amplifiers (PGA). After selection of a

combination of input and reference signals VIN and VREF, the input voltage is modulated and amplified through

stages 1 to 3. Fine gain programming up to 1'000V/V is possible. In addition, the last two stages provide

programmable offset. Each amplifier can be bypassed if needed.

The output of the PGA stages is directly fed to the analog-to-digital converter (ADC), which converts the signal

VIN,ADC into digital.

Like most ADCs intended for instrumentation or sensing applications, the ZoomingADC™ is an over-sampled

converter (See Note1). The ADC is a so-called incremental converter, with bipolar operation (the ADC accepts both

positive and negative input voltages). In first approximation, the ADC output result relative to full-scale (FS) delivers

the quantity:

1 Note: Over-sampled converters are operated with a sampling frequency fS much higher than the input signal's Nyquist rate (typically fS is 20-

1'000 times the input signal bandwidth). The sam pling frequency to throughput rati o is large (typically 10-500). These converte rs include digital

decimation filtering. They are mainly used for high resolution, and/or low-to-medium speed applications.

16-5

XE8805/05A

2/2/

REF

ADCIN

ADC V

OUT ≅ (Eq. 1)

in two's complement (see Sections 16.4 and 16.7 for details). The output code OUTADC is -FS/2 to +FS/2 for VIN,ADC

≅ -VREF/2 to +VREF/2 respectively. As will be shown in section 16.6, VIN,ADC is related to input voltage VIN by the

relationship:

REFTOTINTOTADCIN VGDoffVGDV ⋅−⋅=

, (V) (Eq. 2)

where GDTOT is the total PGA gain, and GDoffTOT is the total PGA offset.

PGA1 PGA2 PGA3

ADC

MUX

Acquisit ion Chain

GD1 GD2 GD3

OFF2 OFF3

AC_A

AC_R

RegACOutLSB

RegACOutMSB

Sampling Frequency f

ADC Busy Flag

Default Settings

Conversion Start

Nbr of Elementary Cycles

Over-Sampling Ratio

Continuous vs. On-Request

Power Saving Modes

PGA Enabling

RegACCfg5

RegACCfg4

RegACCfg3

RegACCfg2

RegACCfg1

RegACCfg0

5 2 4 7 7

Inputs

REF

IN,ADC

MUX

Figure 16-2. ZoomingADC™ detailed functional block diagram

16-6

XE8805/05A

16.4.2 Peripheral Registers

Figure 16-2 shows a detailed functional diagram of the ZoomingADC™.

In table 16-10 the configuration of the peripheral registers is detailed. The system has a bank of eight 8-bit

registers: six registers are used to configure the acquisition chain (RegAcCfg0 to 5), and two registers are used

to store the output code of the analog-to-digital conversion (RegAcOutMsb & Lsb). The register coding of the

ADC parameters and performance characteristics are detailed in Section 16.7.

Table 16-10. Peripheral registers to configure the acquisition chain (AC)

and to store the analog-to-digital conversion (ADC) result

Bit Position

Name 7 6 5 4 3 2 1 0

RegAcOutLsb OUT[7:0]

RegAcOutMsb OUT[15:8]

RegAcCfg0

Default values: START

0 SET_NELC[1:0]

01 SET_OSR[2:0]

010 CONT

0 TEST

RegAcCfg1

Default values: IB_AMP_ADC[1:0]

11 IB_AMP_PGA[1:0]

11 ENABLE[3:0]

0001

RegAcCfg2

Default values: FIN[1:0]

00 PGA2_GAIN[1:0]

00 PGA2_OFFSET[3:0]

0000

RegAcCfg3

Default values: PGA1_G

0 PGA3_GAIN[6:0]

0000000

RegAcCfg4

Default values:

0 PGA3_OFFSET[6:0]

0000000

RegAcCfg5

Default values: BUSY

0 DEF

0 AMUX[4:0]

00000 VMUX

With:

• OUT: (r) digital output code of the analog-to-digital converter. (MSB = OUT[15])

• START: (w) setting this bit triggers a single conversion (after the current one is finished). This bit always reads back 0.

• SET_NELC: (rw) sets the number of el ementary conversions to 2SET_NELC[1:0] . To compens ate for offsets, the input signal

is chopped between elementary conversions (1,2,4,8).

• SET_OSR: (rw) sets the over-sampling rate (OSR) of an elementary conversion to 2(3+SET_OSR[2:0]) . OSR = 8, 16, 32, ...,

512, 1024.

• CONT: (rw) setting this bit starts a conversion. A new conversion will autom aticall y begin as long as the bit remains at 1.

• TEST: bit only used for test purposes. In normal mode, this bit is forced to 0 and cannot be overwritten.

• IB_AMP_ADC: (rw) sets the bias current in the ADC to 0.25*(1+ IB_AMP_ADC[1:0]) of the normal operation current (25,

50, 75 or 100% of nominal current). To be used for low-power, low-speed operation.

• IB_AMP_PGA: (rw) sets the bias current in the PGAs to 0.25*(1+IB_AMP_PGA[1:0]) of the normal operation current (25,

50, 75 or 100% of nominal current). To be used for lo w-power, low-speed operation.

• ENABLE: (rw) enables the ADC modulator (bit 0) and the different stages of the PGAs (PGAi by bit i=1,2,3). PGA stages

that are disabled are bypassed.

• FIN: (rw) These bits set the sampling frequency of the acquisition chain. Expressed as a fraction of the oscillator freque ncy,

the sampling frequenc y is given as: 00 Æ 1/4 fRC, 01 Æ 1/8 fRC, 10 Æ 1/32 fRC, 11Æ ~8kHz.

• PGA1_GAIN: (rw) sets the gain of the first stage: 0 Æ 1, 1 Æ 10.

• PGA2_GAIN: (rw) sets the gain of the second stage: 00 Æ 1, 01 Æ 2, 10 Æ 5, 11 Æ 10.

• PGA3_GAIN: (rw) sets the gain of the third stage to PGA3_GAIN[6:0]⋅1/12.

• PGA2_OFFSET: (rw) sets the offset of the second stage b etween –1 and +1, with increments of 0.2. The MSB gives the sign

(0 → positive, 1 → negative); amplitude is coded with the bits PGA2_OFFSET[5:0].

• PGA3_OFFSET: (rw) sets the offset of the third stage between –5.25 and +5.25, with increments of 1/12. T he MSB gives the

sign (0 → positive, 1 → negative); amplitude i s coded with the bits PGA3_OFFSET[5:0].

16-7

XE8805/05A

• BUSY: (r) set to 1 if a conversion is running. Note that the flag is set at the effective start of the conversion. Since the ADC is

generally synchronized on a lower frequency clock than the CPU, there might be a small delay (max. 1 cycle of the ADC

sampling frequency) between the writing of the START or CONT bits and the appe arance of BUSY flag.

• DEF: (w) sets all values to their defaults (PGA disabled, max speed, nominal modulator bias current, 2 elementary

conversions, over-sampling rate of 32) and starts a new conversion without waiting the end of the preceding one.

• AMUX(4:0): (rw) AMUX[4] sets the mode (0 Æ 4 differential inputs, 1 Æ 7 inputs with A(0) = common reference)

AMUX(3) sets the sign (0 Æ straight, 1Æ cross) AMUX[2:0] sets the channel.

• VMUX: (rw) sets the differential reference channel (0 Æ R(1) and R(0), 1 Æ R(3) and R(2)).

(r = read; w = write; rw = read & write)

16-8

XE8805/05A

16.4.3 Continuous-Time vs. On-Request

The ADC can be operated in two distinct modes: "continuous-time" and "on-request" modes (selected using the bit

CONT).

In "continuous-time" mode, the input signal is repeatedly converted into digital. After a conversion is finished, a new

one is automatically initiated. The new value is then written in the result register, and the corresponding internal

trigger pulse is generated. This operation is sketched in Figure 16-3. The conversion time in this case is defined as

TCONV.

Internal Trig

Ouput Code

RegACOut[15:0]

CONV

BUSY

IRQ

Figure 16-3. ADC "continuous-time" operation

Figure 16-4. ADC "on-request" opera tion

In the "on-request" mode, the internal behaviour of the converter is the same as in the "continuous-time" mode, but

the conversion is initiated on user request (with the START bit). As shown in Figure 16-4, the conversion time is

also TCONV. Note that the flag is set at the effective start of the conversion. Since the ADC is generally synchronized

on a lower frequency clock than the CPU, there might be a small delay (max. 1 cycle of the ADC sampling

frequency) between the writing of the START or CONT bits and the appearan ce of BUSY flag.

Internal Trig

Ouput Code

RegACOut[15:0]

TCONV

Request

START

BUSY

IRQ

16-9

XE8805/05A

16.5 Input Multiplexers

The ZoomingADC™ has eight analog inputs AC_A(0) to AC_A(7) and four reference inputs AC_R(0) to

AC_R(3). Let us first define the differential input voltage VIN and reference voltage VREF respectively as:

INNINPIN VVV −= (V) (Eq. 3)

and:

REFNREFPREF VVV −= (V) (Eq. 4)

As shown in Table 16-11 the inputs can be configured in two ways: either as 4 differential channels (VIN1 =

AC_A(1) - AC_A(0),..., VIN4 = AC_A(7) - AC_A(6)), or AC_A(0) can be used as a common reference, providing

7 signal paths all referred to AC_A(0). The control word for the analog input selection is AMUX[4:0]. Notice that

the bit AMUX[3] controls the sign of the input voltage.

AMUX[4:0]

(RegAcCfg5[5:1]) VINP V

INN AMUX[4:0]

(RegAcCfg5[5:1]) VINP V

INN

00x00

00x01

00x10

00x11

AC_A(1)

AC_A(3)

AC_A(5)

AC_A(7)

AC_A(0)

AC_A(2)

AC_A(4)

AC_A(6)

01x00

01x01

01x10

01x11

AC_A(0)

AC_A(2)

AC_A(4)

AC_A(6)

AC_A(1)

AC_A(3)

AC_A(5)

AC_A(7)

10000

10001

10010

10011

10100

10101

10110

10111

AC_A(0)

AC_A(1)

AC_A(2)

AC_A(3)

AC_A(4)

AC_A(5)

AC_A(6)

AC_A(7)

AC_A(0)

11000

11001

11010

11011

11100

11101

11110

11111

AC_A(0)

AC_A(1)

AC_A(2)

AC_A(3)

AC_A(4)

AC_A(5)

AC_A(6)

AC_A(7)

Table 16-11. Analog input selection

Similarly, the reference voltage is chosen among two differential channels (VREF1 = AC_R(1)-AC_R(0) or VREF2 =

AC_R(3)-AC_R(2)) as shown in Table 16-12. The selection bit is VMUX. The reference inputs VREFP and VREFN

(common-mode) can be up to the power supply range.

16-10

XE8805/05A

VMUX

(RegAcCfg5[0]) VREFP V

REFN

0 AC_R(1) AC_R(0)

1 AC_R(3) AC_R(2)

Table 16-12. Analog Reference input selection

16.6 Programmable Gain Amplifiers

As seen in Figure 16-1, the zooming function is implemented with three programmable gain amplifiers (PGA).

These are:

• PGA1: coarse gain tuning

• PGA2: medium gain and offset tuning

• PGA3: fine gain and offset tuning

All gain and offset settings are realized with ratios of capacitors. The user has control over each PGA activation

and gain, as well as the offset of stages 2 and 3. These functions are examined hereafter.

ENABLE[3:0] Block

xxx0

xxx1 ADC disabled

ADC enabled

xx0x

xx1x PGA1 disabled

PGA1 enabled

x0xx

x1xx PGA2 disabled

PGA2 enabled

0xxx

1xxx PGA3 disabled

PGA3 enabled

Table 16-13. ADC & PGA enabling

PGA1_GAIN PGA1 Gain

GD1 (V/V)

0 1

1 10

Table 16-14. PGA1 Gain Settings

PGA2_GAIN[1:0] PGA2 Gain

GD2 (V/V)

00 1

01 2

10 5

11 10

Table 16-15. PGA2 gain settings

16-11

XE8805/05A

PGA2_OFFSET[3:0] PGA2 Offset

GDoff2 (V/V)

0000 0

0001 +0.2

0010 +0.4

0011 +0.6

0100 +0.8

0101 +1

1001 -0.2

1010 -0.4

1011 -0.6

1100 -0.8

1101 -1

Table 16-16. PGA2 offset settings

PGA3_GAIN[6:0] PGA3 Gain

GD3 (V/V)

0000000 0

0000001 1/12(=0.083)

... ...

0000110 6/12

... ...

0001100 12/12

0010000 16/12

...

0100000 32/12

...

1000000 64/12

...

1111111 127/12(=10.58)

Table 16-17. PGA3 gain settings

PGA3_OFFSET[6:0] PGA3 Offset

GDoff3 (V/V)

0000000 0

0000001 +1/12(=+0.083)

0000010 +2/12

... ...

0010000 +16/12

... ...

0100000 +32/12

... ...

0111111 +63/12(=+5.25)

1000000 0

1000001 -1/12(=-0.083)

1000010 -2/12

... ...

1010000 -16/12

... ...

1100000 -32/12

... ...

1111111 -63/12(=-5.25)

Table 16-18. PGA3 offset settings

16-12

XE8805/05A

16.6.1 PGA & ADC Enabling

Depending on the application objectives, the user may enable or bypass each PGA stage. This is done according to

the word ENABLE and the coding given in Table 16-13. To reduce power dissipation, the ADC can also be

inactivated while idle.

16.6.2 PGA1

The first stage can have a buffer function (unity gain) or provide a gain of 10 (see Table 16-14). The voltage VD1 at

the output of PGA1 is:

IND VGDV ⋅= 11 (V) (Eq. 5)

where GD1 is the gain of PGA1 (in V/V) controlled with the bit PGA1_GAIN.

16.6.3 PGA2

The second PGA has a finer gain and offset tuning capability, as shown in Table 16-15 and Table 16-16. The

voltage VD2 at the output of PGA2 is given by:

REFDD VGDoffVGDV ⋅−⋅= 2122 (V) (Eq. 6)

where GD2 and GDoff2 are respectively the gain and offset of PGA2 (in V/V). These are controlled with the words

PGA2_GAIN[1:0] and PGA2_OFFSET[3:0].

As shown in equation 6, the offset correction is directly proportional to the reference voltage. All drifts and

perturbations on the reference voltage will affect the precision of the offset compensation.

16.6.4 PGA3

The finest gain and offset tuning is performed with the third and last PGA stage, according to the coding of Table

16-17 and Table 16-18. The output of PGA3 is also the input of the ADC. Thus, similarly to PGA2, we find that the

voltage entering the ADC is given by:

REFDADCIN VGDoffVGDV ⋅−⋅= 323, (V) (Eq. 7)

where GD3 and GDoff3 are respectively the gain and offset of PGA3 (in V/V). The control words are

PGA3_GAIN[6:0] and PGA3_OFFSET[6:0] . To remain within the signal compliance of the PGA stages, the

condition:

DDDD VVV <

21 , (V) (Eq. 8)

must be verified.

As shown in equation 7, the offset correction is directly proportional to the reference voltage. All drifts and

perturbations on the reference voltage will affect the precision of the offset compensation.

16-13

XE8805/05A

Finally, combining equations Eq. 5 to Eq. 7 for the three PGA stages, the input voltage VIN,ADC of the ADC is related

to VIN by:

REFTOTINTOTADCIN VGDoffVGDV ⋅−⋅=

, (V) (Eq. 9)

where the total PGA gain is defined as:

123 GDGDGDGDTOT ⋅⋅= (V/V) (Eq. 10)

and the total PGA offset is:

233 GDoffGDGDoffGDoffTOT ⋅+= (V/V) (Eq. 11)

16.7 ADC Characteristics

The main performance characteristics of the ADC (resolution, conversion time, etc.) are determined by three

programmable para meters:

• sampling frequency fS,

• over-sampling ratio OSR, and

• number of elementary conversions NELCONV.

The setting of these parameters a nd the resulting performances a re described hereafter.

16.7.1 Conversion Sequence

A conversion is started each time the bit START or the bit DEF is set. As depicted in Figure 16-5, a complete

analog-to-digital conversion sequence is made of a set of NELCONV elementary incremental conversions and a final

quantization step. Each elementary conversion is made of (OSR+1) sampling periods TS=1/fS, i.e.:

SELCONV fOSRT /)1( += (s) (Eq. 12)

The result is the mean of the elementary conversion results. An important feature is that the elementary

conversions are alternatively performed with the offset of the internal amplifiers contributing in one direction and the

other to the output code. Thus, converter internal offset is eliminated if at least two elementary sequences are

performed (i.e. if NELCONV ≥ 2). A few additional clock cycles are also required to initiate and end the conversion

properly.

Conversion index

Offset

TELCONV= (OSR+1)/fS

Elementary

Conversion

Elementary

Conversion

Elementary

Conversion

NELCONV

- 1

Elementary

Conversion

NELCONV

Init End

TCONV

Conversion

Result

Figure 16-5. Analog-to-di gital conversion sequence

16-14

XE8805/05A

16.7.2 Sampling Frequency

The word FIN[1:0] is used to select the sampling frequency fS (Table 16-19). Three sub-multiples of the internal

RC-based frequency fRCEXT can be chosen. For FIN = "11", sampling frequency is about 8kHz. Additional

information on oscillators and their control can be found in the clock block documentation.

Sampling Frequency fS (Hz)

FIN[1:0] 01/05 02

00 1/4⋅fRC 1/8⋅fRCEXT

01 1/8⋅fRC 1/16⋅fRCEXT

10 1/32⋅fRC 1/64⋅fRCEXT

11 ∼8kHz ∼4kHz

Table 16-19. Sampling frequency settings (fRC= RC-based frequency)

16.7.3 Over-Sampling Ratio

The over-sampling ratio (OSR) defines the number of integration cycles per elementary conversion. Its value is set

with the word SET_OSR[2:0] in power of 2 steps (see Table 16-20) given by:

0]:SET_OSR[23

=OSR (-) (Eq. 13)

SET_OSR[2:0]

(RegAcCfg0[4:2]) Over-Sampling Ratio

OSR (-)

000 8

001 16

010 32

011 64

100 128

101 256

110 512

111 1024

Table 16-20. Over-sampling ratio settings

16.7.4 Elementary Conversions

As mentioned previously, the whole conversion sequence is made of a set of NELCONV elementary incremental

conversions. This number is set with the word SET_NELC[1:0] in power of 2 steps (see Table 16-21) given by:

0]:SET_NELC[1

ELCONV

N (-) (Eq. 14)

16-15

XE8805/05A

SET_NELC[1:0]

(RegAcCfg0[6:5])

# of Elementary

Conversions

NELCONV (-)

00 1

01 2

10 4

11 8

Table 16-21. Number of elementary conversion settings

As already mentioned, NELCONV must be equal or greater than 2 to reduce interna l amplifier offsets.

16.7.5 Resolution

The theoretical resolution of the ADC, without considering thermal noise, is given by:

)(log)(log2 22 ELCONV

NOSRn +⋅= (Bits) (Eq. 15)

000 001 010 011 100 101 110 111

SET

OSR

Resolution - n [Bits]

SET

NELC=

Figure 16-6. Resolution vs. SET_OSR[2:0] and SET_NELC[2:0]

SET_NELC

SET_OSR

[2:0] 00 01 10 11

000 6 7 8 9

001 8 9 10 11

010 10 11 12 13

011 12 13 14 15

100 14 15 16 16

101 16 16 16 16

110 16 16 16 16

111 16 16 16 16

(shaded area: resolution truncated to 16 bits

due to output register size RegAcOut[15:0])

Table 16-22. Resolution vs. SET_OSR[2:0] and SET_NELC[1:0] settings

Using look-up Table 16-22 or the graph plotted in Figure 16-6, resolution can be set between 6 and 16 bits. Notice

that, because of 16-bit register use for the ADC output, practical resolution is limited to 16 bits, i.e. n ≤ 16. Even

if the resolution is truncated to 16 bit by the output register size, it may make sense to set OSR and NELCONV to

higher values in order to reduce the influence of the thermal noise in the PGA (see section 16.8.4).

16-16

XE8805/05A

16.7.6 Conversion Time & Throughput

As explained using Figure 16-5, conve rsion time is given by:

SELCONVCONV fOSRNT /)1)1(( ++⋅= (s) (Eq. 16)

and throughput is then simply 1/TCONV. For example, consider an over-sampling ratio of 256, 2 elementary

conversions, and a sampling frequency of 500kHz (SET_OSR = "101", SET_NELC = "01", fRC = 2MHz, and FIN =

"00"). In this case, using Table 16-23, the conversion time is 515 sampling periods, or 1.03ms. This corresponds to

a throughput of 971Hz in continuous-time mode. The plot of Figure 16-7 illustrates the classic trade-off between

resolution and conversion time.

SET_NELC[1:0] SET_OSR

[2:0] 00 01 10 11

000 10 19 37 73

001 18 35 69 137

010 34 67 133 265

011 66 131 261 521

100 130 259 517 1033

101 258 515 1029 2057

110 514 1027 2053 4105

111 1026 2051 4101 8201

Table 16-23. Normalized conv ersion time (TCONV

⋅

fS) vs. SET_OSR[2:0] and

SET_NELC[1:0](normalized to sampling period 1/fS)

4.0

6.0

8.0

10.0

12.0

14.0

16.0

10.0 100.0 1000.0 10000.0

Normalized Conversion Time - T

CONV

[-]

Resolution - n [Bits]

SET_NELC

01 10 11

Figure 16-7. Resolution vs. normalized conversion time for different SET_NELC[1:0]

16.7.7 Output Code Format

The ADC output code is a 16-bit word in two's complement format (see Table 16-24). For input voltages outside the

range, the output code is saturated to the closest full-scale value (i.e. 0x7FFF or 0x8000). For resolutions smaller

than 16 bits, the non-significant bits are forced to the values shown in Table 16-25. The output code, expressed in

LSBs, corresponds to:

OSR

OUT

REF

ADCIN

ADC 1

16 +

⋅⋅= (LSB) (Eq.17)

Recalling equation Eq. 9, this can be rewritten as:

16-17

XE8805/05A

⎟

⎠

⎞

⎜

⎝

⎛⋅−⋅⋅=

REF

TOTTOT

REF

ADC V

GDoffGD

OUT 16

2 OSR

OSR 1

⋅ (LSB) (Eq. 18)

where, from Eq. 10 and Eq. 11, the total PGA gain and offset are respectively:

123 GDGDGDGDTOT ⋅⋅= (V/V)

and:

233 GDoffGDGDoffGDoffTOT ⋅+= (V/V)

ADC Input

Voltage

VIN,ADC

% of

Full

Scale

(FS)

Output in

LSBs

Output

Code

in Hex

+2.49505V +0.5⋅FS +215-1

=+32'767 7FFF

+2.49497V ... +215-2

=+32'766 7FFE

... ... ... ...

+76.145µV ... +1 0001

0V 0 0 0000

-76.145µV ... -1 FFFF

... ... ... ...

-2.49505V ... -215-1

=-32'767 8001

-2.49513V -0.5⋅FS -215

=-32'768 8000

Table 16-24. Basic ADC Relationships (example for: VREF = 5V, OSR = 512, n = 16 bits)

SET_OSR

[2:0] SET_NELC = 00 SET_NELC = 01 SET_NELC = 10 SET_NELC = 11

000 1000000000 100000000 10000000 1000000

001 10000000 1000000 100000 10000

010 100000 10000 1000 100

011 1000 100 10 1

100 10 1 - -

101 - - - -

110 - - - -

111 - - - -

Table 16-25. Last forced LSBs in conversion output registers for resolution settings smaller than 16

bits (n < 16) (RegAcOutMsb[7:0] & RegAcOutLsb[7:0])

16-18

XE8805/05A

The equivalent LSB size at the input of the PGA chai n is:

⋅⋅= OSR

OSR

LSB

TOT

REF

n (V) (Eq. 19)

Notice that the input voltage VIN,ADC of the ADC must satisfy the condition:

)(

⋅−⋅≤ OSR

OSR

VVV REFNREFPADCIN (V) (Eq. 20)

to remain within the ADC input range.

16.7.8 Power Saving Modes

During low-speed operation, the bias current in the PGAs and ADC can be programmed to save power using the

control words IB_AMP_PGA[1:0] and IB_AMP_ADC[1:0] (see Table 16-26). If the system is idle, the PGAs and

ADC can even be disabled, thus, reducing power consumption to its minimum. This can considerably improve

battery lifetime.

IB_AMP_ADC

[1:0]

IB_AMP_PGA

[1:0]

ADC

Bias

Current

PGA

Bias

Current

Max. fS

[kHz]

1/4⋅IADC

1/2⋅IADC

3/4⋅IADC

IADC

62.5

125

250

500

1/4⋅IPGA

1/2⋅IPGA

3/4⋅IPGA

IPGA

62.5

125

250

500

Table 16-26. ADC & PGA power saving modes an d maximum sampling frequency

16.8 Specifications and Measured Curves

This section presents measurement results for the acquisition chain. A summary table with circuit specifications

and measured curves are given.

16-19

XE8805/05A

16.8.1 Default Settings

Unless otherwise specified, the measurement conditions are the following:

• Temperature TA = +25°C

• VDD = +5V, GND = 0V, VREF = +5V, VIN = 0V

• RC frequency fRC = 2MHz, sampling frequency fS = 500kHz

• Offsets GDOff2 = GDOff3 = 0

• Power operation: norm al (IB_AMP_ADC[1:0] = IB_AMP_PGA[1:0] = '11')

• Resolution: for n = 12 bits: OSR = 32 and NELCONV = 4

for n = 16 bits: OSR = 512 and NELCONV = 2

16-20

XE8805/05A

16.8.2 Specifications

Unless otherwise specified: Temperature TA = +25°C, VDD = +5V, GND = 0V, VREF = +5V, VIN = 0V, RC frequency fRC = 2MHz, sampling

frequency fS = 500kHz, Overall PGA gain GDTOT = 1, offsets GDOff2 = GDOff3 = 0. Power operation: normal (IB_AMP_ADC[1:0] =

IB_AMP_PGA[1:0] = '11'). For resolution n = 12 bits: OSR = 32 and NELCONV = 4. For resolution n = 16 bits: OSR = 512 and NELCONV = 2.

VALUE

PARAMETER MIN TYP MAX

UNITS COMMENTS/CONDITIONS

ANALOG INPUT

CHARACTERISTICS

Differential Input Voltage Ranges

VIN = (VINP - VINN)

Reference Voltage Range

REF = (VREFP – VREFN)

-2.42

-24.2

-2.42

+2.42

+24.2

+2.42

VDD

Gain = 1, OSR = 32 (Note 1)

Gain = 100, OSR = 32

Gain = 1000, OSR = 32

PROGRAMMABLE GAIN

AMPLIFIERS (PGA)

Total PGA Gain, GDTOT

PGA1 Gain, GD1

PGA2 Gain, GD2

PGA3 Gain, GD3

Gain Setting Precision (each stage)

Gain Temperature Dependence

Offset

PGA2 Offset, GDoff2

PGA3 Offset, GDoff3

Offset Setting Precision (PGA2 or 3)

Offset Temperature Dependence

Input Impedance

PGA1

PGA2, PGA3

Output RMS Noise

PGA1

PGA2

PGA3

0.5

-3

-1

-127/12

-3

1500

150

±0.5

±5

±0.5

±5

205

340

365

1000

127/12

+127/12

V/V

ppm/°C

V/V

ppm/°C

kΩ

µV

See Table 16-14

See Table 16-15

Step=1/12 V/V, See Table

16-17

Step=0.2 V/V, See Table 16-16

Step=1/12 V/V, See Table

16-18

(Note 2)

PGA1 Gain = 1 (Note 3)

PGA1 Gain = 10 (Note 3)

Maximal gain (Note 3)

(Note 4)

(Note 5)

(Note 6)

ADC STATIC PERFORMANCE

Resolution, n

No Missing Codes

Gain Error

Offset Error

Integral Non-Linearity, INL

Resolution n = 16 Bits

Differential Non-Linearity, DNL

Resolution n = 16 Bits

Power Supply Rejection Ratio, PSRR

±0.15

±1

±1.0

±0.5

Bits

% of FS

LSB

(Note 7)

(Note 8)

(Note 9)

n = 16 bits (Note 10)

(Note 11)

(Note 12)

VDD = 5V ± 0.3V (Note 13)

VDD = 3V ± 0.3V (Note 13)

DYNAMIC PERFORMANCE

Sampling Frequency, fS

Conversion Time, TCONV

Throughput Rate (Continuous Mode),

1/TCONV

Nbr of Initialization Cycles, NINIT

Nbr of End Conversion Cycles, NEND

PGA Stabilization Delay

133

1027

3.76

0.49

OSR

kHz

cycles/fS

kSps

cycles

n = 12 bits (Note 14)

n = 16 bits (Note 14)

n = 12 bits, fS = 500kHz

n = 16 bits, fS = 500kHz

(Note 15)

DIGITAL OUTP UT

ADC Output Data Coding

Binary Two’s Complement

See Table 16-24 and Table

16-25

16-21

XE8805/05A

Specifications (Cont’d)

VALUE

PARAMETER MIN TYP MAX

UNITS COMMENTS/CONDITIONS

POWER SUPPLY

Voltage Supply Range, VDD

Analog Quiescent Current

Consumption, Total (IQ)

ADC Only

PGA1

PGA2

PGA3

Analog Power Dissipation

Normal Power Mode

3/4 Power Reduction Mode

1/2 Power Reduction Mode

1/4 Power Reduction Mode

+2.4

720/620

250/190

165/150

130/120

175/160

3.6/1.9

2.7/1.4

1.8/0.9

0.9/0.5

+5.5

µA

Only Acquisition Chain

VDD = 5V/3V

All PGAs & ADC Active

VDD = 5V/3V (Note 16)

VDD = 5V/3V (Note 17)

VDD = 5V/3V (Note 18)

VDD = 5V/3V (Note 19)

TEMPERATURE

Specified Range

Operating Range

-40

+85

+125

°C

Notes:

(1) Gain defined as overall PGA gain GDTOT = GD1⋅GD2⋅GD3. Maximum input voltage is given by:

VIN,MAX = ±(VREF/2)⋅(OSR/OSR+1).

(2) Offset due to tolerance on GDoff2 or GDoff3 setting. For small intrinsic offset, use only ADC and PGA1.

(3) Measured with block connected to inputs through AMUX block. Normalized input sampling frequency for input impedance is fS =

512kHz. This figure must be multiplied by 2 for fS = 256kHz, 4 for fS = 128kHz. Input impedance is proportional to 1/fS.

(4) Figure independent from PGA1 gain and sampling frequency fS. See model of Figure 16-18(a).

See equation Eq. 21 to calculate equivalent input noise.

(5) Figure independent on PGA2 gain and sampling frequency fS. See model of Figure 16-18(a). See equation Eq. 21 to calculate

equivalent input noise.

(6) Figure independent on PGA3 gain and sampling frequency fS. See model of Figure 16-18(a) and equation Eq. 21 to calculate

equivalent input noise.

(7) Resolution is given by n = 2⋅log2(OSR) + log2(NELCONV). OSR can be set between 8 and 1024, in powers of 2. NELCONV can be set to

1, 2, 4 or 8.

(8) If a ramp signal is applied to the input, all digital codes appear in the resulting ADC output data.

(9) Gain error is defined as the amount of deviation between the ideal (theoretical) tr ansfer function and the measured tr ansfer function

(with the offset error removed). (See Figure 16-19)

(10) Offset error is defined as the output code error for a zero volt input (ideally, output code = 0). For ± 1 LSB offset, NELCONV must be ≥2.

(11) INL defined as t he deviation of the DC transfer curve of each individual code from the best-fit straight line. This specification holds

over the full scale.

(12) DNL is defined as the difference (in LSB) between the ideal (1 LSB) and measured code transitions for successive codes.

(13) Figures for Gains = 1 to 100. PSRR is defined as the amount of change in the ADC output value as the power supply voltage

changes.

(14) Conversion time is given by: TCONV = (NELCONV ⋅ (OSR + 1) + 1) / fS. OSR can be set bet ween 8 and 1 024, in po wers of 2. NELCONV can

be set to 1, 2, 4 or 8.

(15) PGAs are reset after each writing operation to registers RegAcCfg1-5. The ADC must be started after a PGA or inputs common-

mode stabilisation delay. This is done by writing bit Start several cycles after PGA settings modification or channel switching.

Delay between PGA start or input channel s witching and ADC start should be equivalent to OSR (between 8 and 1024) number of

cycles. This delay does not apply to conversions made without the PGAs.

(16) Nominal (maximum) bias currents in PGAs and ADC, i.e. IB_AMP_PGA[1:0] = ‘11’ and IB_AMP_ADC[1:0] = ‘11’.

(17) Bias currents in PGAs and ADC set to 3/4 of nominal values, i.e. IB_AMP_PGA[1:0] = ‘10’, IB_AMP_ADC[1:0] = ‘10’.

(18) Bias currents in PGAs and ADC set to 1/2 of nominal values, i.e. IB_AMP_PGA[1:0] = ‘01’, IB_AMP_ADC[1:0] = ‘01’.

(19) Bias currents in PGAs and ADC set to 1/4 of nominal values, i.e. IB_AMP_PGA[1:0] = ‘00’, IB_AMP_ADC[1:0] = ‘00’.

16.8.3 Linearity

16.8.3.1 Integral non-linearity

The integral non-linearity depends on the selected gain configuration. First of all, the non-linearity of the ADC (all

PGA stages bypassed) is shown in Fig ure 16-8.

16-22

XE8805/05A

Figure 16-8. Integral non-linearity of the ADC (PGA disabled, r eference voltage of 4.8V)

The different PGA stages have been designed to find the best compromise between the noise performance, the

integral non-linearity and the power consumption. To obtain this, the first stage has the best noise performance and

the third stage the best linearity performance. For large input signals (small PGA gains, i.e. up to about 50), the

noise added by the PGA is very small with respect to the input signal and the second and third stage of the PGA

should be used to get the best linearity. For small input signals (large gains, i.e. above 50), the noise level in the

PGA is important and the first stage of the PGA should be used.

The following figures give the non-linearity for different gain settings of the PGA, selecting the appropriate stage to

get the best noise and linearity performance. Figure 16-9 shows the non-linearity when the third stage is used with

a gain of 1. It is of course not very useful to use the PGA with a gain of 1 unless it is used to compensate offset. By

increasing the gain, the integral non-linearity beco mes even smaller since the signal in the amplifiers reduces.

Figure 16-10 shows the non-linearity for a gain of 2. Figure 16-11 shows the non-linearity for a gain of 5. Figure

16-12 shows the non-linearity for a gain of 10. By comparing these figures to Figure 16-8, it can be seen that the

third stage of the PGA does not add significant integ r al non-linearity.

Figure 16-13 shows the non-linearity for a gain of 20 and Figure 16-14 shows the non-linearity for a gain of 50. In

both cases the PGA2 is used at a gain of 10 and the remaining gain is realized by the third stage. It can be seen

again that the second stage of the PGA does not add signifi cant non-linearity.

For gains above 50, the first stage PGA1 should be selected in stead of PGA2. Although the non-linearity in the first

stage of the PGA is larger than in stage 2 and 3, the gain in stage 3 is now sufficiently high so that the non-linearity

of the first stage does become negligible as is shown in Figure 16-15 for a gain of 100. Therefor, the first stage is

preferred over the second stage since it has less noise.

Increasing the gain further up to 1000 will further increase the linearity since the signal becomes very small in the

first two stages. The signal is full scale at the output of stage 3 and as shown in Figure 16-9 to Figure 16-12, this

stage has very good linearity.

16-23

XE8805/05A

Figure 16-9. Integral non-linearity of the ADC and with gain of 1 (PGA1 and PGA2 disabled, PGA3=1,

reference voltage of 5V)

Figure 16-10. Integral non-linearity of the ADC and gain of 2 (PGA1 and PGA2 disabled, PGA3=2

reference voltage of 5V)

Figure 16-11. Integral non-linearity of the ADC and gain of 5 (PGA1 and PGA2 disabled, PGA3=5,

reference voltage of 5V)

16-24

XE8805/05A

Figure 16-12. Integral non-linearity of the ADC and gain of 10 (PGA1 and PGA2 disabled, PGA3=10,

reference voltage of 5V)

Figure 16-13. Integral non-linearity of the ADC and gain of 20 (PGA1 and PGA2=10, PGA3=2,

reference voltage of 5V )

16-25

XE8805/05A

Figure 16-14. Integral non-linearity of the ADC and gain of 50 (PGA1 disabled, PGA2=10, PGA3=5,

reference voltage of 5V)

Figure 16-15. Integral non-linearity of the ADC and gain of 100 (PGA1=10 and PGA3=10, PGA2

disabled, reference voltage of 5V)

16.8.3.2 Differential non-linearity

The differential non-linearity is generated by the ADC. The PGA does not add differential non-linearity. Figure

16-16 shows the differential non-linearity.

16-26

XE8805/05A

Figure 16-16. Differential non-linearity of the ADC converter.

16.8.4 Noise

Ideally, a constant input voltage VIN should result in a constant output code. However, because of circuit noise, the

output code may vary for a fixed input voltage. Thus, a statistical analysis on the output code of 1200 conversions

for a constant input voltage was performed to derive the equivalent noise levels of PGA1, PGA2, and PGA3. The

extracted rms output noise of PGA1, 2, and 3 are given in Table 16-27: standard output deviation and output rms

noise voltage. Figure 16-17 shows the distribution for the ADC alone (PGA1, 2, and 3 bypassed). Quantization

noise is dominant in this case, and, thus, the ADC thermal noise is below 16 bits.

The simple noise model of Figure 16-18(a) is used to estimate the equivalent input referred rms noise VN,IN of the

acquisition chain in the model of Figure 16-1 8(b). This is given by the relationship:

)(

))/(())/(()/( 2

3213

212

,ELCONV

NNN

INN NOSR

GDGDGDVGDGDVGDV

V⋅

⋅⋅+⋅+

= (V2rms) (Eq. 21)

where VN1, VN2, and VN3 are the output rms noise figures of Table 16-27, GD1, GD2, and GD3 are the PGA gains of

stages 1 to 3 respectively. As shown in this equation, noise can be reduced by increasing OSR and NELCONV

(increases the ADC averaging effect, but reduces noise).

Parameter PGA1 PGA2 PGA3

Standard deviation at

ADC output (LSB) 0.85 1.4 1.5

Output rms noise (µV) 1 205 (VN1) 340 (VN2) 365 (VN3)

Note: see noise model of Figure 16-18 and equation Eq. 21.

Table 16-27. PGA noise measurem ents (n = 16 bits, OSR = 512, NELCONV = 2, VREF = 5V)

16-27

XE8805/05A

-5 -4 -3 -2 -1 0 1 2 3 4 5

Output Code Deviation From Mean Value [LSB]

Occurences

[% of total samples]

Figure 16-17. ADC noise (PGA1, 2 & 3 bypassed, OSR=512,NELCONV=2)

PGA1 PGA2 PGA3

ADC

GD1 GD2 GD3

(a)

PGA1 PGA2 PGA3

ADC

GD1 GD2 GD3

N,IN

(b)

Figure 16-18. (a) Simple noise model for PGAs and ADC

and (b) total input referred noise

As an example, consider the system where: GD2 = 10 (GD1 = 1; PGA3 bypassed), OSR = 512, NELCONV = 2, VREF =

5V. In this case, the noise contribution VN1 of PGA1 is dominant over that of PGA2. Using equation Eq. 21, we get:

VN,IN = 6.4µV (rms) at the input of the acquisition chain, or, equivalently, 0.85 LSB at the output of the ADC.

Considering a 0.2V (rms) maximum signal amplitude, the signal-to-noise ratio is 90dB.

Noise can also be reduced by implementing a software filter. By making an average on a number of subsequent

measurements, the apparent noise is reduced the square root of the number of measurement used to make the

average.

16.8.5 Gain Error and Offset Error

Gain error is defined as the amount of deviation between the ideal transfer function (theoretical equation Eq. 18)

and the measured transfer function (with the offset error removed).

The actual gain of the different stages can vary depending on the fabrication tolerances of the different elements.

Although these tolerances are specified to a maximum of ±3%, they will be most of the time around ±0.5%.

Moreover, the tolerances between the different stages are not correlated and the probability to get the maximal

error in the same direction in all stages is very low. Finally, these gain errors can be calibrated by the software at

the same time with the gain errors of the sensor for instance.

Figure 16-19 shows gain error drift vs. temperature for different PGA gains. The curves are expressed in % of Full-

Scale Range (FSR) normalized to 25°C.

16-28

XE8805/05A

Offset error is defined as the output code error for a zero volt input (ideally, output code = 0). The offset of the ADC

and the PGA1 stage are completely suppressed if N ELCONV > 1.

The measured offset drift vs. temperature curves for different PGA gains are depicted in Figure 16-20. The output

offset error, expressed in LSB for 16-bit setting, is normalized to 25°C. Notice that if the ADC is used alone, the

output offset error is below ±1 LSB and has no drift.

NORMALIZED TO 25°C

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

-50 -25 0 25 50 75 100

Temperature [ °C ]

Gain Error [% of FSR]

100

Figure 16-19. Gain error vs. temperature for different PGA gains

NORMALIZED TO 25°C

-40

-20

100

-50 -25 0 25 50 75 100

Temperature [° C ]

Ou tput Off s e t Erro r [LSB]

100

Figure 16-20. Offset error vs. temperature for different PGA gains

16.8.6 Power Consumption

Figure 16-21 plots the variation of quiescent current consumption with supply voltage VDD, as well as the

distribution between the 3 PGA stages and the ADC (see Table 16-28). As shown in Figure 16-22, if lower

sampling frequency is used, the quiescent current consumption can be lowered by reducing the bias currents of the

PGAs and the ADC with registers IB_AMP_PGA [1:0] and IB_AMP_ADC [1:0]. (In Figure 16-22,

IB_AMP_PGA/ADC[1:0] = '11', '10', '00' for fS = 500, 250, 62.5kHz respe ctively.)

Quiescent current consumption vs. temperature is depicted in Figure 16-23, showing a relative increase of nearly

40% between -45 and +85°C. Figure 16-24 shows the variation of quiescent current consumption for different

frequency settings of the internal RC oscillator. It can be seen that the quiescent current varies by about 20%

between 100kHz and 2MHz.

16-29

XE8805/05A

100

200

300

400

500

600

700

800

2.5 3.0 3.5 4.0 4.5 5.0 5.5

Supply Voltage - V

DDA

[V]

Quiesc ent Cu rrent - I

[µA]

No PGA s , A DC o n ly

PGA1 + ADC

PG A1 & 2 + ADC

PG A1, 2 & 3 + ADC

Figure 16-21. Quiescent curren t con sumption vs. supply voltage

100

200

300

400

500

600

700

800

2.5 3.0 3.5 4.0 4.5 5.0 5.5

Supply V olta g e - V

DDA

[V]

Quiesc ent Current - I

[µA]

500kHz

Sampling Frequ ency f

250kHz

62.5kHz

Figure 16-22. Quiescent curren t con sumption vs. supply voltage for differe nt sampling frequencies

500

550

600

650

700

750

800

850

900

-50 -25 0 25 50 75 100 125

Temperature [°C]

Quiescent Current - I

[µA]

-25

-20

-15

-10

-5

-50 -25 0 25 50 75 100 125

Temperature [°C]

Relative Quiescent Current Change

/ I

Q,25°C

[%]

(a) (b)

Figure 16-23. (a) Absolute and (b ) relative change inquiescent current consumption vs. temperature

16-30

XE8805/05A

Supply ADC PGA1

PGA2 PGA3 TOTAL Unit

VDD = 5V 250 165 130 175 720 µA

VDD = 3V 190 150 120 160 620 µA

Table 16-28. Typical quiescen t current distributions in acquisition chain (n = 16 bits, fS = 500kHz)

-20

-15

-10

-5

0 500 1000 1500 2000 2500 3000 3500

Fr eq uency - f

[kHz]

Relat ive Q u iescent Cur ren t Change

∆I

/ I

Q,2MHz

[% ]

500

550

600

650

700

750

800

850

0 500 1000 1500 2000 2500 3000 3500

Frequency - f

[kHz]

Quiescent Current - I

[µA]

(a) (b)

Figure 16-24. (a) Absolute and (b) relative cha nge in quiescent curent consumption vs. RC oscillator

frequency (all PGAs active, VDD = 5V)

16.8.7 Power Supply Rejection Ratio

Figure 16-25 shows power supply rejection ratio (PSRR) at 3V and 5V supply voltage, and for various PGA gains.

PSRR is defined as the ratio (in dB) of voltage supply change (in V) to the change in the converter output (in V).

PSRR depends on both PGA gain and sup ply voltage VDD.

100

105

1 5 10 20 100

PGA Gain [V/V]

PSRR [dB]

VDD=3V

VDD=5V

Figure 16-25. Power supply rejection ratio (PSRR)

16-31

XE8805/05A

Supply GAIN = 1 GAIN =5 GAIN = 10 GAIN = 20 GAIN =100 Unit

VDD = 5V 79 78 100 99 97 dB

VDD = 3V 72 79 90 90 86 dB

Table 16-29. PSRR (n = 16 bits, V IN = VREF = 2.5V, fS = 500kHz)

16.9 Application Hints

16.9.1 Input Impedance

The PGAs of the acquisition chain employ switched-capacitor techniques. For this reason, while a conversion is

done, the input impedance on the selected channel of the PGAs is inversely proportional to the sampling frequency

fS and to stage gain as given in equation 22.

gainf Hz

in ⋅

Ω⋅

≥9

10768 (Eq. 22)

The input impedance observed is the input impedance of the first PGA stage that is enabled or the input

impedance of the ADC if all three stages are disabled.

PGA1 (with a gain of 10), PGA2 (with a gain of 10) and PGA3 (with a gain of 10) each have a minimum input

impedance of 150kΩ at fS = 512kHz (see Specification Table). Larger input impedance can be obtained by

reducing the gain and/or by reducing the sampling frequency. Therefor, with a gain of 1 and a sampling frequency

of 100kHz, Zin > 7.6MΩ.

The input impedance on channels that are not selected is very high (>100MΩ).

16.9.2 PGA Settling or Input Channel Modifications

PGAs are reset after each writing operation to registers RegAcCfg1-5. Similarly, input channels are switched after

modifications of AMUX[4:0] or VMUX. To ensure precise conversion, the ADC must be started after a PGA or

inputs common-mode stabilization delay. This is done by writing bit START several cycles after PGA settings

modification or channel switching. Delay between PGA start or input channel switching and ADC start should be

equivalent to OSR (between 8 and 1024) number of cycles. This delay does not apply to conversions made without

the PGAs.

If the ADC is not settled within the specified period, there is most probably an input impedance problem (see

previous section).

16.9.3 PGA Gain & Offset, Linearity and Nois e

Hereafter are a few design guideline s th at should be taken into account when using the Zoomi ngADC™:

1) Keep in mind that increasing the overall PGA gain, or "zooming" coefficient, improves linearity but

degrades noise perform ance.

2) Use the minimum number of PGA stages necessary to produce the desired gain ("zooming") and offset.

Bypass unnecessary PGAs.

3) For high gains (>50), use PGA stage 1. For low gains (<50) use stage s 2 and 3.

4) For the lowest noise, set the highest possible gain on the first (front) PGA stage used in the chain. For

example, in an application where a gain of 20 is needed, set the gain of PGA2 to 10, set the gain of PGA3

to 2.

16-32

XE8805/05A

4) For highest linearity and lowest noise performance, bypass all PGAs and use the ADC alone (applications

where no "zooming" is needed); i.e. set ENABLE[3:0] = '0001'.

5) For low-noise applications where power consumption is not a primary concern, maintain the largest bias

currents in the PGAs and in the ADC; i.e. set IB_AMP_PGA[1:0] = IB_AMP_ADC[1:0] = '11'.

6) For lowest output offset error at the output of the ADC, bypass PGA2 and PGA3. Indeed, PGA2 and

PGA3 typically introduce an offset of about 5 to 10 LSB (16 bit) at their output. Note, however, that the

ADC output offset is easily calibrated out by software.

16.9.4 Frequency Response

The incremental ADC is an over-sampled converter with two main blocks: an analog modulator and a low-pass

digital filter. The main function of the digital filter is to remove the quantization noise introduced by the modulator.

As shown in Figure 16-26, this filter determines the frequency response of the transfer function between the output

of the ADC and the analog input VIN. Notice that the frequency axes are normalized to one elementary conversion

period OSR/fS. The plots of Figure 16-26 also show that the frequency response changes with the number of

elementary conversions NELCONV performed. In particular, notches appear for NELCONV ≥ 2. These notches occur at:

ELCONV

NOTCH NOSR fi

if ⋅

⋅

=)( (Hz) for )1(,...,2,1

−

ELCONV

Ni (Eq. 23)

and are repeated every fS/OSR.

Information on the location of these notches is particularly useful when specific frequencies must be filtered out by

the acquisition system. For example, consider a 5Hz-bandwidth, 16-bit sensing system where 50Hz line rejection is

needed. Using the above equation and the plots below, we set the 4th notch for NELCONV = 4 to 50Hz, i.e.

1.25⋅fS/OSR = 50Hz. The sampling frequency is then calculated as fS = 20.48kHz for OSR = 512. Notice that this

choice yields also good attenuation of 50Hz harmonics.

0.2

0.4

0.6

0.8

1.2

01234

Norma l i zed Frequency - f *(OSR/f

) [-]

Normalized Magnitude [-]

ELCONV

= 1

0.2

0.4

0.6

0.8

1.2

01234

Normalized Frequency - f *(OSR/f

) [-]

Nor ma lized M agn itude [-]

ELCONV

= 2

0.2

0.4

0.6

0.8

1.2

01234

Normaliz ed Fre quency - f *(OSR/f

) [-]

Nor mal ize d M agn itu d e [-]

ELCONV

= 4

0.2

0.4

0.6

0.8

1.2

01234

Normalized Frequency - f *(OSR/fS) [-]

Nor mal ize d M agn itude [-]

ELCONV

= 8

Figure 16-26. Frequency response: normalized magnitude v s. frequency for different NELCONV

16-33

XE8805/05A

16.9.5 Power Reduction

The ZoominADC™ is particularly well suited for low-power applications. When very low power consumption is of

primary concern, such as in battery operated systems, several parameters can be used to reduce power

consumption as follows:

1) Operate the acquisition chain with a redu ced supply voltage VDD.

2) Disable the PGAs which are not used during analog -to-digital conversion with ENABLE[3:0].

3) Disable all PGAs and the ADC when the system is id le and no conversion is performed.

4) Use lower bias currents in the PGAs and the ADC using the control words IB_AMP_PGA[1:0] and

IB_AMP_ADC[1:0]. (This reduces the maximum sampling frequency according to Table 16-26.)

5) Reduce internal RC oscillator frequency and/or sam pling frequency.

Finally, remember that power reduction is typically traded off with reduced linearity, larger noise and slower

maximum sampling speed.

17-1

XE8805/05A

17. Vmult (Voltage Multiplier)

17.1 Features 17-2

17.2 Overview 17-2

17.3 Control register 17-2

17.4 External component 17-2

17-2

XE8805/05A

17.1 Features

• Generates a voltage that is higher or equal to the supply voltage.

• Can be easily enabled or disabled

17.2 Overview

The Vmult block generates a voltage (called “Vmult”) that is higher or equal to the supply voltage. This output

voltage is used in the acquisition chain.

The voltage multiplier should be on (bit ENABLE in RegVmultCfg0) when using the acquisition chain or analog

properties of the Port B while VBAT is below 3V. If the multiplier is enabled, the external capacitor on the pin

VMULT is mandatory.

The source clock of Vmult is selected by FIN[1:0] in RegVmultCfg0. It is strongly recommended to use the same

settings as in the ADC.

17.3 Control register

There is only one register in the Vmult. Table 177-1 describes the bits in the register.

Pos. RegVmultCfg0 rw Reset Function

2 Enable rw 0

resetsystem enable of the vmult

‘1’ : enabled

‘0’ : disabled

1-0 Fin rw 0

resetsystem system clock division factor

‘00’ : 1/2,

‘01’ : 1/4,

‘10’ : 1/16,

‘11’ : 1/64

Table 177-1. RegVmultCfg0

17.4 External component

When the multiplier is enabled, a capacitor has to be connected to the VMULT pin. If the multiplier is disabled, the

pin may remain floating.

Min. Max. Note

Capacitor on VMULT 1.0 3.0 nF

18-1

XE8805/05A

18. Signal D/A (DAS)

18.1 Features 18-2

18.2 Overview of Signal DAC - The generic DAC 18-2

18.3 Registers Map 18-3

18.4 The D/A description 18-4

18.4.1 What is a noise shaper ? 18-4

18.4.2 Advantages/disadvantages 18-4

18.4.3 D/A setup and resolution 18-5

18.5 Amplifier 18-7

18.6 Low pass filter 18-8

18.6.1 First order low pass filter 18-8

18.6.2 Second order low pass filter 18-9

18.7 4-20mA loop 18-10

18.7.1 2-wire loop with first order filtering 18-10

18.7.2 2-wire loop with second order filtering 18-12

18-2

XE8805/05A

18.1 Features

• 16-bits maximum input word width

• Synchronization mechanism to guarantee data integrity when writing LSB and MSB 8-bits data

• Programmable noise shaper order: second, first or order zero

• Programmable PWM modulation between 4 and 11-bits

• Programmable clock input frequency: fin or fin/2

• Programmable output polarity: active high or low

• On chip amplifier for analog filtering, voltage output or 4-20 mA loop

18.2 Overview of Signal DAC - The generic DAC

The generic DAC block consists of two major parts: the noise shaper (sigma-delta modulator) and the PWM

modulator as shown in Figure 18-1.

control Sigma-delta

modulator

PWM

modulator

CPU

bus 16 4-11

DAS Out

amp

Figure 18-1. General block diagram

A D/A converter that is built with a digital PWM modulator needs a high clock frequency for a small signal

bandwidth. For a 10 bit digital PWM modulator for instance, a 10 bit counter is needed in order to create a pulse

with a resolution of 1024. This means that, in case an infinitely sharp analog output filter is used, the clock

frequency has to be at least 1024 times the output bandwidth. In practice however, in order to be able to build the

analog filter, the clock frequency needs to be much higher.

In order to reduce this frequency requirement, the input digital word is broken down into n words with a smaller

width m by a noise shaper so that the “average” (average for first order noise shaper, more complicated for higher

order noise shapers) value of the n m-bit words represents the full width input code. Instead of 1 pulse with the full

resolution, the PWM modulator now generates n pulses with a smaller resolution m. This increases the output

pulse repetition frequency with a factor n for identical clock frequency. Therefore, the analog output filtering is

easier to implement. Higher order noise shapers (order >1) allow to decrease the clock frequency for identical

signal bandwidth.

Another advantage is that the signal distortion is less dependent on the signal value. A disadvantage is however,

that the output signal after filtering is more dependent on the rise and fall times of the PWM output since there are

many more pulses.

The maximum word width at the input is 16-bit. If the word is narrower, 0’s have to be added after the LSB. In order

to maintain maximum flexibility, the order of the noise shaper and the resolution of the PWM modulation are

programmable by writing the codes CodeLmax and NsOrder to the configuration register. The possible noise

shaper order is 0 (which means no noise shaping), 1 or 2. The possible PWM modulation resolution m can be set

between 4 and 11.

18-3

XE8805/05A

18.3 Registers Map

All registers are reset with the system reset.

The contents of the registers RegDasInLsb and RegDasInMsb are transferred to the D/A converter when after

data have been written into RegDasInMsb. Therefore, in order to maintain the synchronisation between the LSB

and MSB, the LSB should always be written before the MSB.

Pos. RegDasInLsb rw reset function

7-0 DasInLsb(7:0) rw 0

resetsystem

Data to convert LSB

Table 18-1. RegDasInLsb

Pos. RegDasInMsb rw reset function

7-0 DasInMsb(7:0) rw 0

resetsystem

Data to convert MSB

Table 18-2. RegDasInMsb

Pos. RegDasCfg0 rw reset function

7:6 NsOrder(1:0) rw 00

resetsystem

Noise Shaper order

00 : order 0

01 : order 1

1x : order 2

5:3 CodeLmax(2:0) rw 000

resetsystem

PWM pulse resolution :

000 : 4 bits

001 : 5 bits

010 : 6 bits

011 : 7 bits

100 : 8 bits

101 : 9 bits

110 : 10 bits

111 : 11 bits

2:1 Enable(1:0) rw 00

resetsystem

Bit 0 : enables the D/A

Bit 1 : enables the amplifier

0 Fin rw 0

resetsystem

Input frequency of modulator as a fraction of

oscillator frequency

0 : 1.fRC, 1 : ½.fRC

Table 18-3. RegDasCfg0

Pos. RegDasCfg1 rw reset function

7:2 - rw 000000 Unused

1 BW rw 0

resetsystem

Amplifier bandwidth

0 : small bandwidth

1 : large bandwidth

0 INV rw 0

resetsystem

Inverts the PWM output

0 : normal, active high

1 : inverted, active low

Table 18-4. RegDasCfg1

18-4

XE8805/05A

18.4 The D/A description

The D/A converter consists of 2 parts: a classic PWM modulator which is preceded by a noise shaper (Figure

18-1). The PWM signal has then to be low pass filtered using the amplifier and external components to obtain the

analog signal.

18.4.1 What is a noise shaper?

The major disadvantage of using a PWM modulator to generate a high resolution analog signal is that it requires a

high ratio between the PWM switching frequency and the useful bandwidth of the output analog signal after low

pass filtering.

Example: assuming the switching frequency of the PWM modulator is 1MHz and one wants to resolve 16 bit, i.e.

216=65536 steps. In this case, the PWM has to code each step in increments of 1µs=1/1MHz and needs therefore

65536µs per pulse. This means that the PWM pulse repetition rate is 1/65536µs=15.25Hz. So, even with a higher

order low pass filter, more than 1 frequency decade will be required to filter the PWM signal down to a 16 bit

accurate analog signal. This leaves a useful bandwidth below 1Hz.

The goal of the noise shaper is to reduce the ratio between the PWM switching frequency and the useful

bandwidth. The noise shaper will not reduce the “truncation noise” and “PWM modulation noise” but move it to

higher frequencies. It “shapes” the frequency spectrum (“noise”) of the generated PWM signal, hence its name. In

practice, the noise shaper allows the generation of a signal with a given resolution using a PWM modulator that

has a lower resolution. The noise shaper then generates a series of different subsequent low resolution codes for

the PWM so that the average value corresponds to the high resolution code.

The first order noise shaper interpolates between two adjacent PWM codes to obtain a higher resolution. The

second order noise shaper can use non-adjacent PWM codes.

Example for first order noise shaper: assuming again the resolution of 16 bits using a 1MHz PWM switching

frequency using the noise shaper with order 1. If a PWM modulator with 4 bits, i.e. 16 steps is used, the PWM

repetition frequency becomes then 1MHz/16=62.5kHz. The PWM modulator can convert only the 4 MSB’s of the

16 bit input such as h0000, h1000 until hF000. In order to convert the code h5800, which is between h5000 and

h6000? In this case, the first order noise shaper will interpolate by presenting alternatively the code h5 and h6 to

the PWM so that after filtering a signal is obtained halfway between the normal PWM steps. To convert the code

h5400, it will present h5 3 times and h6 once to the PWM and so on. It is clear from this that the PWM repetition

frequency is much higher than for the simple PWM and can be filtered out more easily. The quantization noise

frequency will depend on the code to be converted: for this example for instance we need two PWM pulses to

implement the code h5800, but we need four to implement h5400 etc.

Example for second order noise shaper: if we use the same conditions as for the example above, we will obtain the

same PWM repetition frequency. However, to implement the code h5400, the noise shaper now can present the

following sequence to the PWM modulator: h6, h5, h6, h4. This increases the frequency components at the PWM

pulse repetition frequency and ½ of the PWM pulse repetition frequency but at the same time reduces energy at ¼

of the PWM pulse repetition frequency with respect to the first order noise shaper. The low pass cut-off frequency

can therefore be higher than for a first order noise shaper.

A disadvantage of the second order noise shaper is however that the resolution will drop when the code is very

close to h0000 or hFFFF.

Example: if we assume the same conditions as above, but we want to convert the code h0400. It is now impossible

to use a similar sequence as above (which would be h1, h0, h1, h(-1) ) due to saturation of the code. There is no

choice left but the sequence h1 h0 h0 h0 which is the same sequence as in the first order noise shaper.

18.4.2 Advantages/disadvantages

Advantages:

Using a high order noise shaper together with a PWM modulator with low resolution reduces the ratio between the

low pass cut off frequency and the PWM switching frequency for the same total resolution. This can be used to

18-5

XE8805/05A

increase the output signal bandwidth or to reduce the PWM switching frequency and therefore the power

consumption of the D/A. Signal distortion is less dependent on the signal value.

Disadvantages:

Using a high order noise shaper together with a PWM modulator with low resolution will use lots of short pulses in

stead of 1 long pulse. The D/A is therefore more sensitive to rise and fall times of the PWM resulting in a slightly

higher non-linearity and temperature dependence. The second order noise shaper also has a reduced resolution

for codes very close to zero or full scale.

18.4.3 D/A setup and resolution

In this section, the resolution that can be obtained with the D/A as a function of settings is calculated. These

calculations are based on the quantization and PWM modulation noise. Noise on the reference, i.e. the supply

voltage is not taken into account. High frequency noise on the supply voltage can be filtered by the output low pass

filter, but in band noise on the reference will show up in the output signal with amplitude that will depend on the

signal value. Therefore, when using the D/A, one should take care to minimize the switching activity on the digital

ports and/or to limit the load on these ports.

18.4.3.1 Noise shaper of order 0

Setting the noise shaper to order 0 (NsOrder=00), reduces the D/A to a regular PWM. Two parameters are setting

the resolution of the D/A: the resolution of the modulator itself and the amount of low pass filtering at the output.

The modulation width m of the PWM modulator is given by:

CodeLmax+= 4m

The cut-off frequency c

f of the low pass filter required to get the resolution is calculated below. The PWM

modulator repetition frequency PWM

f can be calculated as a function of the selected modulation width m, the

frequency of the RC oscillator of the circuit RC

f and the selected frequency division set by Fin :

PWM

11⎟

⎠

⎞

⎜

⎝

⎛

⋅

=Fin

To obtain an analog signal with the required solution, the PWM signal has to be low pass filtered. The resolution

that can be obtained depends on the filter order and the ratio between the PWM modulation frequency PWM

f and

the filter cut-off frequency c

f. For a low pass filter of LpOrder, we obtain:

⎟

⎠

⎞

⎜

⎝

⎛

⋅=

PWM

PWM f

LpOrderresolution 2

log

The total resolution of the D/A is then the minimal value of both criteria:

),min( PWM

resolutionmresolution =

In Table 18-5 the required cut-off frequency of the low pass filter is shown for a noise shaper of order 0 as a

function of the desired resolution for both a first and second order low pass filter. The PWM modulation factor m

should be chosen equal to the desired resolution.

18-6

XE8805/05A

resolution (bit) m fc for LpOrder=1 (Hz) fc for LpOrder=2 (Hz)

4 4 7812 31250

5 5 1953 11048

6 6 488 3906

7 7 122 1381

8 8 30 488

9 9 7.6 172

10 10 1.9 61

11 11 0.48 22

Table 18-5. Signal bandwidth as a function of the required resolution for the PWM without noise shaper (Fin=0,

NsOrder=00, fRC=2MHz).

18.4.3.2 Noise shaper of order 1 or 2

The calculation on the required low pass cut-off frequency given in 18.4.3.1 remains valid in this case. However,

the noise shaper allows using smaller PWM modulation for the same resolution. This increases the PWM

modulation frequency and as a consequence increases the output bandwidth.

An additional criterion however shows up: the filtering of the quantization noise. As can be seen from the examples

in 18.4.1, the interpolation between PWM codes generated by the noise shaper introduce sequences at

frequencies below the PWM modulation frequency. Assuming a low pass filter that has at least the same order as

the noise shaper, the resolution is given by (NsOrder≥1) :

⎟

⎠

⎞

⎜

⎝

⎛−⋅++= 65.2)(log359.0 2c

PWM

quant f

NsOrdermresolution

The total resolution of the D/A is then the minimal of both criteria:

),min( PWMquant resolutionresolutionresolution =

Table 18-6 and Table 18-7 show the signal bandwidth that can be obtained as a function of required resolution and

PWM modulation for first and second order noise shapers. It can be seen that these options are useful to obtain

high resolution using low PWM modulation m. For high PWM modulation m, the resolution is limited by the PWM

modulator and adding a noise shaper does not change anything.

NsOrder=1, f

=2MHz, Fin=0, LpOrder=2

Resolution PWM modulation m

(bit) 4567891011

81596.4 1596.4 1596.4 976.6 488.3 244.1 122.1 61.0

9798.2 798.2 798.2 690.5 345.3 172.6 86.3 43.2

10 399.1 399.1 399.1 399.1 244.1 122.1 61.0 30.5

11 199.5 199.5 199.5 199.5 172.6 86.3 43.2 21.6

12 99.8 99.8 99.8 99.8 99.8 61.0 30.5 15.3

13 49.9 49.9 49.9 49.9 49.9 43.2 21.6 10.8

14 24.9 24.9 24.9 24.9 24.9 24.9 15.3 7.6

15 12.5 12.5 12.5 12.5 12.5 12.5 10.8 5.4

16 6.2 6.2 6.2 6.2 6.2 6.2 6.2 3.8

Table 18-6. Low pass cut-off frequency as a function of the selected PMW modulation and required resolution for a

first order noise shaper.

18-7

XE8805/05A

NsOrder=2, f

=2MHz, Fin=0, LpOrder=2

Resolution PWM modulation m

(bit) 4567891011

85638.4 3906.3 1953.1 976.6 488.3 244.1 122.1 61.0

93986.9 2762.1 1381.1 690.5 345.3 172.6 86.3 43.2

10 2819.2 1953.1 976.6 488.3 244.1 122.1 61.0 30.5

11 1993.5 1381.1 690.5 345.3 172.6 86.3 43.2 21.6

12 1409.6 976.6 488.3 244.1 122.1 61.0 30.5 15.3

13 996.7 690.5 345.3 172.6 86.3 43.2 21.6 10.8

14 704.8 488.3 244.1 122.1 61.0 30.5 15.3 7.6

15 498.4 345.3 172.6 86.3 43.2 21.6 10.8 5.4

16 352.4 244.1 122.1 61.0 30.5 15.3 7.6 3.8

Table 18-7. Low pass cut-off frequency as a function of the selected MPW modulation and required resolution for a

second order noise shaper.

The output range of the D/A is for code 0h0000 is VSS and for code 0hFFFF is (VBAT-VSS)(2m-1)/2m.

18.5 Amplifier

The amplifier can be used to implement the low pass filter and/or a 4-20mA loop. The amplifier is enabled using the

bit Enable(1)=1. The amplifier has two different modes selected by the bit BW: a low frequency mode (BW=0) that

allows driving a high capacitive load and a high frequency mode (BW=1).

The first mode is particularly adapted when a voltage output is used. The second mode is more adapted for a 4-

20mA loop since loads are small and higher bandwidth is required to reject current consumption changes in the

loop.

Table 18-8 shows the specification of the amplifier.

Note that the amplifier can not be used to generate signals that are larger than the supply voltages VBAT and VSS

since the amplifier inputs and outputs are clamped to these voltages. The amplifier inputs and outputs should stay

within the input and output ranges specified below.

18-8

XE8805/05A

sym description min typ max unit Comment

gain gain at DC 80 100 dB 1

GBW0 gain bandwidth product 25 70 kHz 6

CL0 capacitive load 5 nF 6

GBW1 gain bandwidth product 250 450 kHz 7

CL1 capacitive load 200 pF 7

φm phase margin 55 65 ° 8

RL resistive load 5 kΩ 5

SR slew rate 10 30 kV/s 9

CMR common mode input range VSS-0.2 VBAT-1.2 V 2

OR output range VSS+0.2 VBAT-0.2 V

Voff offset ±5 mV

CMRR common mode rejection 60 dB 3

noise integrated input noise 50 100 uVrms

PSRR power supply rejection

ratio

20 60 dB 4

Iquie quiescent bias current 150 uA

Ioff off current 1 uA

1. For the minimal resistive load and the maximal capacitive load

2. The amplifier common mode is VSS in the 4-20mA loop.

3. At DC

4. At DC. Only a low rejection ratio is needed since the D/A output refers directly to the power supplies.

5. Short circuit protection at >3mA.

6. GBW when the maximal load is cl0 and with the bit BW=0

7. GBW when the maximal load is cl1 and with the bit BW=1

8. In both cases BW=0 and BW=1 for the maximal capacitive load and the minimal resistive load.

9. For maximal load CL0, BW=0 and maximal resistive load RL

Table 18-8. Specification of the amplifier.

18.6 Low pass filter

Several low pass filters are proposed here as examples. Other filter types are possible depending on the features

or constraints of the application.

If the filter is inverting the signal, the bit INV can be used to invert the D/A output. This inversion does not need to

be done by calculation.

A first or second order low pas filter can be built with the amplifier. If higher order filters are needed, additional first

or second order sections can be added using external amplifiers.

18.6.1 First order low pass filter

Figure 18-2 shows a possible implementation of a first order low pass filter. Ideally, the analog ground should be

halfway between VBAT and VSS. The gain G and cut-off frequency fc of such a filter are given by:

As an example, to obtain a 1kHz filter with unity gain, we can choose C=1nF and R1=R2=150kΩ.

18-9

XE8805/05A

XE88xx

DAS_OUT

DAS_AI_M

DAS_AO

DAS_AI_P

amp

analog ground

Figure 18-2. First order low pass filter.

18.6.2 Second order low pass filter

Figure 18-3 shows an example of a second order low pass filter using the multi-feedback architecture. The gain G,

cut-off frequency fc and the damping factor ξ (or quality factor Q) as a function of the factors k and m (see Figure

18-3) are given by:

kmnRC

kmn

)1(

−=

For a second order Butterworth filter, 22=

. For smaller damping factors, the filter is under damped resulting

in overshoots on the step response. For higher damping factors, the filter is over damped resulting in a smooth but

slower step response.

An example of a 1dB ripple Chebychev filter with a cut-off frequency of about 1.5kHz and a DC gain of 1 is given

by choosing m=0.22, k=1, n=0.5, R=330kΩ and C=1nF. The resistor nR can be rounded to 180kΩ.

A 60Hz unity gain low pass Butterworth filter can be built choosing R=180kΩ, C=12nF, k=1, m=0.183, n=8.33.

Note that parasitic capacitors between the DAS_OUT node and the filter output DAS_AO will adversely affect the

high frequency behavior of the filter. Care should be taken when routing these signals.

18-10

XE8805/05A

XE88xx

DAS_OUT

DAS_AI_M

DAS_AO

DAS_AI_P

amp

analog ground

R C

mC kR

Figure 18-3. Second order low pass filter.

18.7 4-20mA loop

18.7.1 2-wire loop with first order filtering

The amplifier can be used to build a 4-20mA loop externally. Figure 18-4 shows the principle of such a 2-wire loop

using a first order low pass filter.

In a 2-wire loop, the current consumption of the sensor and read-out electronics is drawn on the same wires as the

signal current. The current consumption of the sensor and read-out electronics should therefore remain below

4mA. The signal current is then added by the bipolar transistor. The resistors Rlim1 and Rlim2 are added to protect

the bipolar transistor against high transient currents during power-up. Rlim1 is generally set to a few kΩ. The value

of Rlim2 is chosen as a function of the external loop voltage VEXT and the transistor saturation voltage VCEsat.

mAmARVVR senseCEsatEXT 20)20(

2lim ⋅

−

−=

If VEXT is larger than 5.5V, a voltage regulator has to be inserted. Since the quiescent current of the regulator adds

up to the 4mA budget, a component with sufficiently low quiescent current has to be selected.

The resistor Rsense measures the total current in the loop (if Rsense<<Rf2). The resistors Rf1 and Rf2 are used to set

the gain and Rf2 and Cf to set the bandwidth of the filter. The resistor Roffset adds an offset to the filter voltage so

that the code 0 of the D/A corresponds to 4mA. The amplifier will force a current through the bipolar transistor so

that the voltage on the filter Vf and VSS on Rsense is equal. This transforms the filter voltage into a loop current

Iloop=(VSS-VEXT-)/Rsense.

18-11

XE8805/05A

The resistor value Rsense is generally chosen between 50Ω and 150Ω resulting in a 1V to 3V voltage drop at

maximal loop current. The resistor Rf2 is then chosen much larger depending on the current error requirement.

Allowing for an error of 0.1% gives Rf2=Rsense/0.001.

The resistor Roffset may be omitted but it will reduce the useful code range of the D/A.

Using the large bandwidth of the amplifier is recommended since this increases the rejection of supply current

variations of the other components in the loop. A bypass capacitor between VBAT and VSS will also reduce the

high frequency current variations. Values will depend on the voltage regulator used. The software in the XE8805

should keep the current supply of the circuit as stable as possible. This means that the clock frequency should kept

constant, peripherals should not be switched on and off, the current in the sensor is kept constant, the processor

should not use the halt or sleep modes, etc.

XE88xx VBAT

DAS_OUT

DAS_AI_P

DAS_AO

DAS_AI_M

VSS

amp

4-20mA

Rsense

Rf1

Rf2 Cf

Rlim1

Rlim2

Voltage

regulator

4-20mA

Roffset

Sensor

VEXT+

VEXT-

VSS

VBAT

Figure 18-4. 2-wire 4-20mA loop with first order filter

The resistor Rf1 can then be calculated to set the full scale D/A code range (depends on the PWM modulation m,

see section 18.4.3.2) equal to the full scale signal current of 16mA:

mAR

RVSSVBAT

sense

f162

)12()( 2

1⋅⋅

⋅−⋅−

≤

The resistor Roffset can be calculated in order to obtain a 4mA current while the D/A code is 0:

mAR

RVSSVBAT

sense

offset 4

)( 2

⋅

⋅−

≤

18-12

XE8805/05A

The capacitor Cf can be calculated from the first order filter cut-off frequency fc :

2ffc

fRRf

As an example, for VBAT-VSS=5V, m=4, Rsense=50Ω, VEXT=30V and a 1kHz low pass filter, we can use:

lim1=1kΩ, Rlim2=1kΩ, Rf1=560kΩ, Rf2=100kΩ, Roffset=2.4MΩ, Cf=1.8nF.

18.7.2 2-wire loop with second order filtering

A second order filter function can be implemented by replacing the resistor Rf1 in Figure 18-4 by another first order

filter section as shown in Figure 18-5. The value of Rf1a+Rf2a has to be chosen the same way as Rf1 in the first order

schematic.

XE88xx VBAT

DAS_OUT

DAS_AI_P

DAS_AO

DAS_AI_M

VSS

amp

4-20mA

Rsense

Rf1a

Rf2

Cf2

Rlim1

Rlim2

Voltage

regulator

4-20mA

Roffset

Sensor

VEXT+

VEXT-

VSS

VBAT

Rf1b

Cf1

Figure 18-5. 2-wire 4-20mA loop with second order filtering.

Another possibility is shown in Figure 18-6. The advantage this solution is that it is easier to stabilize depending on

the component parasitics and board layout. But since it limits the bandwidth of the current regulation loop, it

reduces the rejection of the supply current variations.

For this schematic, all the equations of the first order schematic remain valid. The values of Rfs and Cfs can be

calculated from the cut-off frequency:

fsfs f

For the 1kHz example, we can chose Rfs=150kΩ and Cfs=1nF (set BW=0 in this case).

18-13

XE8805/05A

XE88xx VBAT

DAS_OUT

DAS_AI_P

DAS_AO

DAS_AI_M

VSS

amp

4-20mA

Rsense Rf2

Rlim1

Rlim2

Voltage

regulator

4-20mA

Roffset

Sensor

VEXT+

VEXT-

VSS

VBAT

Rf1

Rfs

Cfs

Figure 18-6. 2-wire 4-20mA with second order filter and increased stability

19-1

XE8805/05A

19. Bias D/A (DAB)

19.1 Features 19-2

19.2 General description 19-2

19.3 Register map 19-2

19.4 D/A specification 19-3

19.5 Amplifier specification 19-3

19.6 Application examples 19-4

19.6.1 Voltage controlled sensor bias 19-4

19.6.2 Current controlled sensor bias 19-4

19-2

XE8805/05A

19.1 Features

• 8 bit low frequency A/D

• On-chip amplifier with 2 terminals MOS output

• Current and voltage controlled applications can be implemented

19.2 General description

Figure 19-1. General block diagram

Figure 19-1 shows the general block diagram of the D/A peripheral. It consists of a control block that manages all

communication with the CPU and sets the configuration of the peripheral. The D/A converts the digital data in an

analog output signal. An amplifier is added that can be used to drive the large sensor currents.

19.3 Register map

The bias D/A has two registers.

Pos. RegDabIn rw reset function

7-0 DabIn(7:0) rw 0

resetsystem

Data to convert

Table 19-1. RegDabIn

Pos. RegDabCfg rw reset function

7-2 r 0 Unused

1-0 Enable(1:0) rw 00

resetsystem

bit 1: enables the amplifier when 1

bit 0: enables the D/A when 1

Table 19-2. RegDabCfg

control

isters

D/A

amp MOS

XE8805A – Bias D/A block

DAB R M

DAB AIM

DAB AOM

DAB AOP

DAB AIP

DAB OUT

DAB R P

VBATT

VSS

DabIn

Enable

As the amplifier is attacking a MOS, effective polarity of the feedback loop

ends on load and network.

19-3

XE8805/05A

19.4 D/A specification

The D/A generates a voltage on node DAB_OUT that is proportional to the code RegDabIn in between the positive

reference voltage DAB_R_P and the negative reference voltage DAB_R_M. The voltage on DAB_R_P always has

to be larger than the voltage on DAB_R_M. The DAB is intended for very low frequency use. The specification is

given in Table 19-3.

The DAB is based on a resistive ladder. Capacitors larger than 100pF are allowed on the node DAB_OUT, but the

step response will increase proportionally.

sym description min typ max unit note

wda number of input bits 8 bits

tstep step response 0.25 1 ms 1

OR D/A output range DAB_R_M DAB_R_P

refp DAB_R_P range VSS+2.3 VBAT V

refn DAB_R_M range VSS VBAT-2.3 V

Rdab impedance between

DAB_R_P and DAB_R_M

1.6 Mohm

1. Time to reach the final value within 5%, CL on DAB_OUT smaller than 100pF.

Table 19-3. D/A specification.

19.5 Amplifier specification

The amplifier output stage is a single transistor follower that is able to drive large currents. This transistor is not

connected internally so that different circuit configurations are possible (see next section). In order to guarantee

correct functionality, the voltage on the output pins has to respect the specifications VRAOP and VRAOM as indicated

in Table 19-4.

sym description min typ max unit Note

gain gain at DC 60 90 dB 1

GBW gain bandwidth product 100 4500 Hz 1

φm phase margin 60 80 ° 1

RL resistive load 300 100000

Ω

CL capacitive load 1 nF

CMR common mode input range VSS VBAT V

VRAOM DAB_AOM voltage range VSS+0.2 DAB_AOP-0.2 V 1

VRAOP DAB_AOP voltage range VSS+2.3 VBAT V 1

Voff offset ±10 mV

noise integrated input noise 60 100 µVrm

Isource max source current 10 40 mA

PSRR power supply rejection ratio 80 dB 2

Ibias quiescent bias current 5 10 µA

Ioff off current 0.1 1 µA

1. For all possible combinations of resistive load and capacitive load.

2. At DC.

Table 19-4. Amplifier specification.

19-4

XE8805/05A

19.6 Application examples

19.6.1 Voltage controlled sensor bias

Figure 19-2 shows the basic connectivity to have a voltage controlled sensor bias. The D/A will generate a voltage

between vrep and vrefn proportional to the input code. The amplifier will copy the D/A voltage to the sensor. The

D/A code can be used to do a software temperature calibration of the sensor for instance.

Filter capacitors can be added in parallel with the sensor reference and signal, on Vrefp, Vrefn and DAB_OUT.

The voltages Vrefp and Vrefn can be filtered before being connected to the D/A reference inputs. The reference

voltages can be connected directly to VBAT and VSS for simplicity. They can also be connected to VBAT and VSS

through a low pass filter that rejects the high frequency supply noise. Finally, in most cases, the voltage range of

interest for the voltage Vsensor on the sensor is only a fraction of the supply voltage. By generating Vrefp and Vrefn

equal to the limits of the voltage range of interest, the resolution of the D/A can be increased. Example: if a supply

of 5V is used and the reference voltage is equal to the supply, the D/A can generate a sensor voltage between 0V

and 5V in steps of about 5V/255≈20mV. If the sensor voltage is always to be between 3V and 4V, and by

connecting Vrefn=3V and Vrefp=4V, the sensor voltage is adjustable between 3V and 4V with steps of about

1V/255≈4mV.

VSS

VBAT or a Reference voltage source

VSS

reference input

of the

ZoomingADC

signal input

of the

ZoomingADC

* Needs a 300 Ω – 100 kΩ load

* Max capacitive load is 1 nF

Vsensor

* High impedance node,

impedance depends on D/A code

Vrefp

Vrefn

XE8805A – DAB block

DAB_R_P

DAB_R_M

DAB_OUT

DAB_AIP

DAB_AOP

DAB_AOM

DAB_AIM

* In this configuration the bridge current and DAB_AOM

increase when DAB_OUT increases.

amp

VBAT

Figure 19-2. Voltage controlled bridge bias principle.

Note that the voltage on the sensor can not be higher than VBAT-0.2V in the example of Figure 19-2 (specification

VRAOM in Table 19-4).

19.6.2 Current controlled sensor bias

Figure 19-3 shows the principle of a current controlled sensor bias schematic. In this case, the amplifier forces the

voltage VR to be equal to the D/A output voltage VD/A. The current Isensor through the sensor is given by:

19-5

XE8805/05A

sense

refnrefp

sense

ADrefp

sense

Rrefp

sensor R

codeVV

I)2551()(

−

⋅

−

The voltage Vsensor can be calculated as a function of the current Isensor and the sensor impedance.

Note that the voltage VR>VSS+2.3V and VR-Vsensor>0.2V (VRAOP and VRAOM specifications in Table 19-4) to

guarantee correct functionality of this schematic.

Choosing the Vrefp equal to the supply voltage or close to the supply voltage in order to have the highest possible

voltage on the sensor is recommended. From the equation, it can be seen that the sensor current step per LSB can

be made smaller by reducing the voltage between Vrefp and Vrefn or by increasing the sense resistor value.

As for the voltage controlled sensor bias, capacitors can be added on several nodes to filter out the noise.

* Voltage must remain above VSS + 2.3 V

* Needs a 300 Ω – 100 k

Ω

load

* Max capacitive load is 1 nF

VSS

* Voltage must remain below VBAT - 2.3 V

* Voltage must remain above VSS + 2.3 V

* In this configuration, the bridge current and DAB_AOM

decrease when DAB_OUT increases.

XE8805A

DAB_R_P

DAB_R_M

DAB_OUT

DAB_AIM

DAB_AOP

DAB_AOM

DAB_AIP

amp

signal

reference

Vrefp

Vrefn

Rsense

Vsensor

VD/A

VSS

Figure 19-3. Current controlled bridge bias

In Figure 19-4, the sense resistor is inserted between the negative reference voltage and the sensor. This

schematic has the same principle as above, but it is easier to respect the limits on VRAOP when VBAT is low. The

sensor current is now:

sense

refnrefp

sense

refnAD

sense

refnR

sensor R

codeVV

I)255()(

⋅

−

In this case, it is recommended to choose Vrefn equal to VSS or close to VSS in order to have the highest possible

voltage on the sensor. The only limit is now Vsensor<VBAT-0.2V.

19-6

XE8805/05A

* Vrefp must remain above VSS + 2.3 V

* Needs a 300 Ω – 100 kΩ kohm load

* Max capacitive load is 1 nF

Vsensor

Vrefp

* In this configuration, the bridge current and DAB_AOM increase

when DAB_OUT increases

XE8805A

DAB_R_P

DAB_R_M

DAB_OUT

DAB_AIP

DAB_AOP

DAB_AOM

DAB_AIM

amp

Vrefn

VD/A

signal input of

ZoomingADC

reference input of

ZoomingADC

Rsense

VBAT

VSS

VBAT or another reference voltage

Figure 19-4. Current controlled sensor bias.

20-1

XE8805/05A

20. Counters/Timers/PWM

20.1 Features 20-2

20.2 Overview 20-2

20.3 Register map 20-2

20.4 Interrupts and events map 20-3

20.5 Block schematic 20-4

20.6 General counter registers operation 20-4

20.7 Clock selection 20-5

20.8 Counter mode selection 20-5

20.9 Counter / Timer mode 20-6

20.10 PWM mode 20-8

20.11 Capture function 20-9

20-2

XE8805/05A

20.1 Features

• 4 x 8-bits timer/counter modules or 2 x 16-bits timers/counter modules

• Each with 4 possible clock sources

• Up/down counter modes

• Interrupt and event generation

• Capture function (internal or external source)

• Rising, falling or both edge of capture signal

• PA[3:0] can be used as clock inputs (debounced or direct)

• 2 x 8 bits PWM or 2 x 16 bits PWM

• PWM resolution of 8, 10, 12, 14 or 16 bits

• Complex mode combinations are possible between counter, capture and PWM modes

20.2 Overview

CounterA and CounterB are 8-bit counters and can be combined to form a 16-bit counter. CounterC and CounterD

exhibit the same features.

The counters can also be used to generate two PWM outputs on PB[0] and PB[1]. In PWM mode one can generate

PWM functions with 8, 10, 12, 14 or 16 bit wide counters.

The counters A and B can be captured by events on an internal or an external signal. The capture can be

performed on both 8-bit counters running individually on two different clock sources or on both counters chained to

form a 16-bit counter. In any case, the same capture signal is used for both counters.

When the counters A and B are not chained, they can be used in several configurations: A and B as counters, A

and B as captured counters, A as PWM and B as counter, A as PWM and B as captured counter.

When the counters C and D are not chained, they can be used either both as counters or counter C as PWM and

counter D as counter.

20.3 Register map

Bit RegCntA rw reset function

7-0 CounterA r xxxxxxxx 8-bits counter value

7-0 CounterA w xxxxxxxx 8-bits comparison value

Table 20-1. RegCntA

bit RegCntB rw reset function

7-0 CounterB r xxxxxxxx 8-bits counter value

7-0 CounterB w xxxxxxxx 8-bits comparison value

Table 20-2. RegCntB

Note: When writing to RegCntA or RegCntB, the processor writes the counter comparison values. When reading

these locations, the processor reads back either the actual counter value or the last captured value if the capture

mode is active.

bit RegCntC rw reset function

7-0 CounterC r xxxxxxxx 8-bits counter value

7-0 CounterC w xxxxxxxx 8-bits comparison value

Table 20-3. RegCntC

20-3

XE8805/05A

bit RegCntD rw reset function

7-0 CounterD r xxxxxxxx 8-bits counter value

7-0 CounterD w xxxxxxxx 8-bits comparison value

Table 20-4. RegCntD

Note: When writing RegCntC or RegCntD, the processor writes the counter comparison values. When reading

these locations, the processor reads back the actual counter value.

bit RegCntCtrlCk rw reset function

7-6 CntDCkSel(1:0) rw xx Counter d clock selection

5-4 CntCCkSel(1:0) rw xx Counter c clock selection

3-2 CntBCkSel(1:0) rw xx Counter b clock selection

1-0 CntACkSel(1:0) rw xx Counter a clock selection

Table 20-5. RegCntCtrlCk

bit RegCntConfig1 rw Reset function

7 CntDDownUp rw x Counter d up or down counting (0=down)

6 CntCDownUp rw x Counter c up or down counting (0=down)

5 CntBDownUp rw x Counter b up or down counting (0=down)

4 CntADownUp rw x Counter a up or down counting (0=down)

3 CascadeCD rw x Cascade counter c & d (1=cascade)

2 CascadeAB rw x Cascade counter a & b (1=cascade)

1 CntPWM1 rw 0 resetsystem Activate pwm1 on counter c or c+d (PB(1))

0 CntPWM0 rw 0 resetsystem Activate pwm0 on counter a or a+b (PB(0))

Table 20-6. RegCntConfig1

bit RegCntConfig2 rw Reset function

7-6 CapSel(1:0) rw 00 resetsystem Capture source selection

5-4 CapFunc(1:0) rw 00 resetsystem Capture function

3-2 Pwm1Size(1:0) rw xx Pwm1 size selection

1-0 Pwm0Size(1:0) rw xx Pwm0 size selection

Table 20-7. RegCntConfig2

bit RegCntOn rw Reset Function

7-4 -- r 0000 Reserved

3 CntDEnable rw 0 resetsystem Enable counter d

2 CntCEnable rw 0 resetsystem Enable counter c

1 CntBEnable rw 0 resetsystem Enable counter b

0 CntAEnable rw 0 resetsystem Enable counter a

Table 20-8. RegCntOn

20.4 Interrupts and events map

Interrupt source Mapping in the

interrupt manager Mapping in the event

manager

IrqA RegIrqHigh(4) RegEvn(7)

IrqB RegIrqLow(5) RegEvn(3)

IrqC RegIrqHigh(3) RegEvn(6)

IrqD RegIrqLow(4) RegEvn(2)

Table 20-9. Interrupt and event mapping.

20-4

XE8805/05A

20.5 Block schematic

PB(0)

Captur e

ck32k

ck1k

PA(0)

RegCntA (write)

Co unt er A

PA(2)

RegCntC (write)

Co unt er C

RegCntD (write)

Co unt er D

RegCntB (write)

Co unt er B

PA(1)

PA(3)

ck128

ckrcext/4

ckr cext

ck1k

ck32k

PWM PB(1)

RegCntA (re ad)

RegCntB (read)

RegCntC (read)

RegCntD (read)

Figure 20-1: Counters/timers block schematic

20.6 General counter registers operation

Counters are enabled by CntAEnable, CntBEnable, CntCEnable, and CntDEnable in RegCntOn.

To stop the counter X, CntXEnable must be reset. To start the counter X, CntXEnable must be set. When

counters are cascaded, CntAEnable and CntCEnable also control respectively the counters B and D.

In the control registers, all registers must be written in this order: RegCntCtrlCk, RegCntConfig1, RegCntConfig2

and all RegCntX because several bits have no default values at reset.

All counters have a corresponding 8-bit read/write register: RegCntA, RegCntB, RegCntC, and RegCntD. When

read, these registers contain the counter value (or the captured counter value). When written, they modify the

counter comparison values.

For a correct acquisition of the counter value, use one of the three following methods:

1) Stop the concerned counter, perform the read operation and restart the counter. While stopped, the

counter content is frozen and the counter does not take into account the clock edges delivered on the

external pin.

20-5

XE8805/05A

2) For slow operating counters (typically at least 8 times slower than the CPU clock), oversample the counter

content and perform a majority operation on the consecutive read results to select the correct actual

content of the counter.

3) Use the capture mechanism.

When a value is written into the counter register while the counter is in counter mode, both the comparison value is

updated and the counter value is modified. In upcount mode, the register value is reset to zero. In downcount

mode, the comparison value is loaded into the counter. Due to the synchronization mechanism between the

processor clock domain and the external clock source domain, this modification of the counter value can be

postponed until the counter is enabled and it receives it’s first valid clock edge.

In the PWM mode, the counter value is not modified by the write operation in the counter register. Changing the

counter mode, does not update the counter value (no load in downcount mode).

20.7 Clock selection

The clock source for each counter can be individually selected by writing the appropriate value in the register

RegCntCtrlCk.

Table 20-10 gives the correspondence between the binary codes used for the configuration bits CntACkSel(1:0),

CntBCkSel(1:0), CntCCkSel(1:0) or CntDCkSel(1:0) and the clock source selected respectively for the counters

A, B, C or D.

Clock source for

CntXCkSel(1:0) CounterA CounterB CounterC CounterD

11 Ck128

10 CkRc/4 Ck1k

01 CkRc Ck32k

00 PA(0) PA(1) PA(2) PA(3)

Table 20-10: Clock sources for counters A, B, C and D

The CkRc clock is the RC oscillator. The clocks below 32kHz can be derived from the RC oscillator or the crystal

oscillator (see the documentation of the clock block). A separate external clock source can be delivered on Port A

for each individual counter.

The external clock sources can be debounced or not by setting the Port A configuration registers.

The clock source can be changed only when the counter is stopped.

20.8 Counter mode selection

Each counter can work in one of the following modes:

1) Counter, downcount & upcount

2) Captured counter, downcount & upcount (only counters A&B)

3) PWM, downcount

The counters A and B or C and D can be cascaded or not. In cascaded mode, A and C are the LSB counters while

B and D are the MSB counters.

Table 20-11 shows the different operation modes of the counters A and B as a function of the mode control bits.

For all counter modes, the source of the down or upcount selection is given (either the bit CntADownUp or the bit

CntBDownUp). Also, the mapping of the interrupt sources IrqA and IrqB and the PWM output on PB(0) in these

different modes is shown.

20-6

XE8805/05A

CascadeAB

CountPWM0

CapFunc(1:0)

Counter A

mode Counter B

mode IrqA

source IrqB

source PB(0)

function

0 0 00

Counter 8b

Downup: A Counter 8b

Downup: B Counter

A Counter

B PB(0)

1 0 00 Counter 16b AB

Downup: A Counter

AB - PB(0)

0 1 00

PWM 8b

Down Counter 8b

Down - Counter

B PWM A

1 1 00 PWM 10 – 16b AB

Down - - PWM AB

0 0

Captured

counter 8b

Downup: A

Captured

counter 8b

Downup: B

Capture

A Capture

B PB(0)

1 0

Captured counter 16b AB

Downup: A Capture

AB Capture

AB PB(0)

0 1

PWM 8b

Down

Captured

counter 8b

Downup: B

Must not

be used Capture

B PWM A

Table 20-11: Operating modes of the counters A and B

Table 20-12 shows the different operation modes of the counters C and D as a function of the mode control bits.

For all counter modes, the source of the down or upcount selection is given (either the bit CntCDownUp or the bit

CntDDownUp). The mapping of the interrupt sources IrqC and IrqD and the PWM output on PB(1) in these

different modes is also shown.

The switching between different modes must be done while the concerned counters are stopped. While switching

capture mode on and off, unwanted interrupts can appear on the interrupt channels concerned by this mode

change.

CascadeCD CountPWM1 Counter C

mode Counter D

mode IrqC

Source IrqD

source PB(1)

function

0 0

Counter 8b

Downup: C Counter 8b

Downup: D Counter

C Counter

D PB(1)

1 0 Counter 16b CD

Downup: C Counter

CD - PB(1)

0 1

PWM 8b

Down Counter 8b

Down - Counter

D PWM C

1 1

PWM 10 – 16b CD

Down - - PWM CD

Table 20-12: Operating modes of the counters C and D

20.9 Counter / Timer mode

The counters in counter / timer mode are generally used to generate interrupts after a predefined number of clock

periods applied on the counter clock input.

Each counter can be set individually either in upcount mode by setting CntXDownUp in the register

RegCntConfig1 or in downcount mode by resetting this bit. Counters A and B can be cascaded to behave as a 16

bit counter by setting CascadeAB in the RegCntConfig1 register. Counters C and D can be cascaded by setting

CascadeCD. When cascaded, the up/down count modes of the counters B and D are defined respectively by the

up/down count modes set for the counters A and C.

20-7

XE8805/05A

When in upcount mode, the counter will start incrementing from zero up to the target value which has been written

in the corresponding RegCntX register(s). When the counter content is equal to the target value, an interrupt is

generated at the next falling edge of counter clock. Then the counter is loaded again with the zero value at the next

rising edge of counter clock (Figure 20-2).

When in downcount mode, the counter will start decrementing from the initial load value which has been written in

the corresponding RegCntX register(s) down to the zero value. Once the counter content is equal to zero, an

interrupt is generated at the next falling edge of counter clock. Then the counter is loaded again with the load value

at the next rising edge of counter clock (Figure 20-2).

Be careful to select the counter mode (no capture, not PWM, specify cascaded or not and up or down counting

mode) before writing any target or load value to the RegCntX register(s). This ensures that the counter will start

from the correct initial value. When counters are cascaded, both counter registers must be written to ensure that

both cascaded counters will start from the correct initial values.

The stopping and consecutive starting of a counter in counter mode without a target or load value write operation in

between can generate an interrupt if this counter has been stopped at the zero value (downcount) or at it’s target

value (upcount). This interrupt is additional to the interrupt which has already been generated when the counter

reached the zero or the target value.

ow n coun

clock counter X

RegcntX

rXX 321032103210

RegCntX

wXX 3

write RegCntX

CntXDownUp

IrqX

CntXEnable

up coun

clock counter X

RegCntX

rXX0 12301230123

RegCntX

wXX 3

write RegCntX

CntXDownUp

IrqX

CntXEnable

Figure 20-2. Up and down count interrupt generation.

20-8

XE8805/05A

20.10 PWM mode

The counters can generate PWM signals (Pulse Width Modulation) on the Port B outputs PB(0) and PB(1).

The PWM mode is selected by setting CntPWM1 and CntPWM0 in the RegCntConfig1 register. See Table 20-11

and Table 20-12 for an exact description of how the setting of CntPWM1 and CntPWM0 affects the operating

mode of the counters A, B, C and D according to the other configuration settings.

When CntPWM0 is enabled, the PWMA or PWMAB output value overrides the value set in bit 0 of RegPBOut in

the Port B peripheral. When CntPWM1 is enabled, the PWMC or PWMCD output value overrides the value set in

bit 1 of RegPBOut. The corresponding ports (0 and/or 1) of Port B must be set in digital mode and as output and

either open drain or not and pull up or not through a proper setting of the control registers of the Port B.

Counters in PWM mode always count down, the CntXDownUp bit setting must be reset. No interrupts and events

are generated by the counters which are in PWM mode. Counters do count circularly: they restart at the maximal

value (either 0xFF when not cascaded or 0xFFFF when cascaded) when respectively an underflow condition

occurs in the counting.

The internal PWM signals are low as long as the counter contents are higher than the PWM code values written in

the RegCntX registers. They are high when the counter contents are smaller or equal to these PWM code values.

The PWM resolution is always 8 bits when the counters used for the PWM signal generation are not cascaded.

PWM0Size(1:0) and PWM1Size(1:0) in the RegCntConfig2 register are used to set the PWM resolution for the

counters A and B or C and D respectively when they are in cascaded mode. The different possible resolutions in

cascaded mode are shown in Table 20-13. Choosing a 16 bit PWM code higher than the maximum value that can

be represented by the number of bits chosen for the resolution, results in a PWM output which is always tied to 1.

PwmXsize(1:0) Resolution

11 16 bits

10 14 bits

01 12 bits

00 10 bits

Table 20-13: Resolution selection in cascaded PWM mode

Small PWM code

Lar ge PWM code

Tper

Thlarge Tllarge

Thsmall Tlsmall

Figure 20-3: PWM modulation examples

The period of the PWM signal is given by the formula:

ckcnt

resolution

Tper 2

20-9

XE8805/05A

The duty cycle ratio DCR of the PWM signal is defined as:

Tper

DCR =

DCR can be selected between 0 % and 100*

212 resolution

resolution − %.

DCR in % in function of the RegCntX content(s) is given by the relation:

resolution

DCR 2RegCntX*100

20.11 Capture function

The 16-bit capture register is provided to facilitate frequency measurements. It provides a safe reading mechanism

for the counters A and B when they are running. When the capture function is active, the processor does not read

anymore the counters A and B directly, but instead reads shadow registers located in the capture block. An

interrupt is generated after a capture condition has been met when the shadow register content is updated. The

capture condition is user defined by selecting either internal capture signal sources derived from the prescaler or

from the external PA(2) or PA(3) ports. Both counters use the same capture condition.

When the capture function is active, the A and B counters must be written with the value 0xFF and can either

upcount or downcount. They do count circularly: they restart at zero or at the maximal value (either 0xFF when not

cascaded or 0xFFFF when cascaded) when respectively an overflow or an underflow condition occurs in the

counting.

CapFunc(1:0) in register RegCntConfig2 determines if the capture function is enabled or not and selects which

edges of the capture signal source are valid for the capture operation. The source of the capture signal can be

selected by setting CapSel(1:0) in the RegCntConfig2 register. For all sources, rising, falling or both edge

sensitivity can be selected. Table 20-14 shows the capture condition as a function of the setting of these

configuration bits.

CapSel(1:0) Selected capture signal CapFunc Selected condition Capture condition

11 1 K

Capture disabled

Rising edge

Falling edge

Both edges

1 K rising edge

1 K falling edge

1 K both edges

10 32 K

Capture disabled

Rising edge

Falling edge

Both edges

32 K rising edge

32 K falling edge

32 K both edges

01 PA3

Capture disabled

Rising edge

Falling edge

Both edges

PA3 rising edge

PA3 falling edge

PA3 both edges

00 PA2

Capture disabled

Rising edge

Falling edge

Both edges

PA2 rising edge

PA2 falling edge

PA2 both edges

Table 20-14: Capture condition selection

CapFunc(1:0) and CapSel(1:0) can be modified only when the counters are stopped otherwise data may be

corrupted during one counter clock cycle.

Due to the synchronization mechanism of the shadow registers and depending on the frequency ratio between the

capture and counter clocks, the interrupts may be generated one or only two counter clock pulses after the

effective capture condition occurred. When the counters A and B are not cascaded and do not operate on the

20-10

XE8805/05A

same clock, the interruptions on IrqA and IrqB which inform that the capture condition was met, may appear at

different moments. In this case, the processor should read the shadow register associated to a counter only if the

interruption related to this counter has been detected.

It must be noted that when counters A and B are cascaded, the capture might happen at different cycles for the A

and B registers. This is due to the asynchronous relationship between counter and capture clock and to the fact

that the capture condition detection is independent for A and B counters.

21-1

XE8805/05A

21 VLD (Voltage Level Detector)

21.1 Features 21-2

21.2 Overview 21-2

21.3 Register map 21-2

21.4 Interrupt map 21-2

21.5 VLD operation 21-2

21-2

XE8805/05A

21.1 Features

• Can be switched off, on or simultaneously with CPU activities

• Generates an interrupt if power supply is below a pre-determined level

21.2 Overview

The Voltage Level Detector monitors the state of the system battery. It returns a logical high value (an interrupt) in

the status register if the supplied voltage drops below the user defined level (Vsb).

21.3 Register map

There are two registers in the VLD, namely RegVldCtrl and RegVldStat. Table 221-1 shows the mapping of

control bits and functionality of RegVldCtrl while Table 221-2 describes that for RegVldStat.

pos. RegVldCtrl rw reset function

7-4 -- r 0000 reserved

3 VldRange r w 0 resetsystem VLD detection voltage range for VldTune = “011”:

0 : 1.3V

1 : 2.55V

2-0 VldTune[2:0] r w 000

resetsystem VLD tuning:

000 : +19 %

111 : -18 %

Table 221-1: RegVldCtrl

pos. RegVldStat rw reset function

7-3 -- r 00000 reserved

2 VldResult r 0 resetsystem is 1 when battery voltage is below the detection

voltage

1 VldValid r 0 resetsystem Indicates when VldResult can be read

0 VldEn r w 0 resetsystem VLD enable

Table 221-2: RegVldStat

21.4 Interrupt map

interrupt source mapping in the interrupt manager

IrqVld RegIrqMid(2)

Table 221-3: Interrupt map

21.5 VLD operation

The VLD is controlled by VldRange, VldTune and VldEn. VldRange selects the voltage range to be detected,

while VldTune is used to fine-tune this voltage level in 8 steps. VldEn is used to enable (disable) the VLD with a

1(0) value respectively.

Disabled, the block will dissipate no power.

21-3

XE8805/05A

symbol description min typ max unit comments

trimming values:

Note 1 VldRange VldTune

1.53 0 000

1.44 0 001

1.36 0 010

1.29 0 011

1.22 0 100

1.16 0 101

1.11 0 110

1.06 0 111

3.06 1 000

2.88 1 001

2.72 1 010

2.57 1 011

2.44 1 100

2.33 1 101

2.22 1 110

Vth Threshold voltage

2.13

1 111

TEOM duration of

measurement 2.0 2.5 ms Note 2

TPW Minimum pulse width

detected 875 1350 us Note 2

Table 221-4: Voltage level detector operation

Note 1: absolute precision of the threshold voltage is ±10%.

Note 2: this timing is respected in case the internal RC or crystal oscillators are enabled

To start the voltage level detection, the user sets bit VldEn. The measurement is started.

After 2ms, the bit VldValid is set to indicate that the measurement results are valid. From that time on, as long as

the VLD is enabled, a maskable interrupt request is sent if the voltage level falls below the threshold. One can also

poll the VLD and monitor the actual measurement result by reading the VldResult bit of the RegVldStat. This

result is only valid as long as the VldValid bit is ‘1’.

An interrupt is generated on each rising edge of VldResult.

22-1

XE8805/05A

22 Physical dimensions

CONTENTS

22.1 QFP type package 22-2

22-2

XE8805/05A

22.1 QFP type package

The QFP package dimensions are given in Figure 22-1 and Table 22-1. The dimensions conform to JEDEC MS-

026 Rev. C.

Figure 22-1. QFP type package

package A

LQFP-64 10.0 12.0 1.4 0.10 0.22 0.5

Table 22-1. QFP package dimensions

22-3

XE8805/05A

Contact In f orma t ion

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Publication thereof does not convey nor imply any license under patent or other industrial or intellectual property rights.

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