DSPIC30F3012T-20E/SO - Microchip Technology

Serial Peripheral

Interface (SPI)

Section 35. Serial Peripheral Interface (SPI) (Part II)

HIGHLIGHTS

This section of the manual contains the following major topics:

35.1 Introduction..................................................................................................................35-2

35.2 SPI Registers.................................... ....................................... ....................................35-3

35.3 Modes of Operati on ................................................................. ....................................35 -8

35.4 Master Mode Clock Frequency..................................................................................35-21

35.5 Operation in Power-Saving Modes............................................................................35-22

35.6 Special Function Registers Associated with the SPI1 Module...................................35-23

35.7 Related Application Notes..........................................................................................35-24

35.8 Revision History.........................................................................................................35-25

dsPIC30F Family Reference Manual

35.1 Introduction

The Serial Peripheral Interface (SPI) module is a synchronous serial interface useful for

communicating with other peripheral or microcontroller devices. These peripheral devices may

be serial EEPROMs, shift registers, display drivers, A/D converters, etc. The SPI module is

compatible with Motorola’s SPI and SIOP interfaces.

Each device in the dsPIC30F SMPS and Digital Power Conversion device family offers one SPI

module, designated SPI1.

The SPI1 serial interface consists of four pins:

• SDI1: Serial Data Input

• SDO1: Serial Data Output

• SCK1: Shift Clock Input or Output

• SS1: Active-Low Slave Select or Frame Synchronization I/O Pulse

The SPI1 module can be configured to operate using 2, 3 or 4 pins. In the 3-pin mode, SS1 is

not used. In the 2-pi n mode, SDO 1 and SS1 are both unused.

A block diagram of the SPI1 module is shown in Figure 35-1.

Figure 35-1: SPI1 Module Block Diagram

Note: Some devices in the dsPIC30F SMPS and Digital Power Conversion device family

do not co ntain th e SS1 pin and, there fore, do n ot include the Framed SPI and Slave

Select functions. Refer to the specific device data sheet for details about available

SPI pins.

Internal Data Bus

SDI1

SDO1

SS1

SCK1

SPI1SR

bit 0

Shift Control

Edge

Select

FCY

Primary

1:1/4/16/64

Enable

Prescaler

Sync

SPI1BUF

Control

Transfer

Write SPI1 BUF

Read SPI1BUF

SPI1CON1<1:0>

SPI1CON1<4:2>

Master Clock

Clock

Control

Secondary

Prescaler

1:1 to 1:8

SPI1RXB SPI1TXB

Section 35. Serial Peripheral Interface (SPI) (Part II)

Serial Peripheral

Interface (SPI )

35.2 SPI Registers

The SPI module consists of a 16-bit shift register, SPI1SR, used for shifting data in and out, and a

buffer register, SPI1B UF. The contr ol registers, SPI1C ON1 and SPI1CON2, co nfigure the module.

Additi on ally, a status register, SPI1STAT, ind ic at es v ari ou s status condi tio ns .

35.2.1 Status and Control Registers

The SPI1STAT, SPI1CON1 and SPI1CON2 registers provide the interface to control the

module ’ s op eration. Th ey are sh own in detail in R egi ste r 35-1, Re gi ste r 35-2 a nd Register 35-3.

• SPI1STAT: SPI1 Status and Control Register

This status register indicates various status conditions such as Receive Overflow,

Transmit Buffer Full and Receive Buffer Full. This register is also used to specify the

operation of the module during Idle mode and contains a bit that enables and disables

the module.

• SP I1CON1: SP I1 Control Register 1

This control register specifies the clock prescaler, Master/Slave mode, Word/Byte

communication, clock polarity and clock/data pin operation.

• SP I1CON2: SP I1 Control Register 2

This control register enables or disables the framed SPI operation. This register also

specifies the frame synchronization pulse direction, polarity and edge selection.

35.2.2 SPI1BUF Register

SPI1BUF is the SPI1 Data Receive/Transmit register. The SPI1BUF register is actually

comprised of two separate registers: the Transmit Buffer, SPI1TXB, and the Receive Buffer,

SPI1RXB. These two unidirectional, 16-bit registers share the SFR address of SPI1BUF. If a user

applic ation w rites dat a to be t ransm itted to the SPI1BUF add ress, inte rnally the dat a is writ ten to

the SPI1TXB register. Similarly, when the user application reads the received data from

SPI1BUF, internally th e data is read from the SPI1RXB re gister.

This technique double buffers transmit and receive operations and allows continuous data

transfers in the background. Transmission and reception occur simultaneously.

In addition, there is a 16-bit shift register, SPI1SR, that is not memory mapped. It is used for

shif tin g data in and out of the SPI port.

dsPIC30F Family Reference Manual

Upper Byte:

R/W-0 U-0 R/W-0 U-0 U-0 U-0 U-0 U-0

SPIEN — SPISIDL — — — — —

bit 15 bit 8

Lower Byte:

U-0 R/C-0 U-0 U-0 U-0 U-0 R-0 R-0

— SPIROV — — — — SPITBF SPIRBF

bit 7 bit 0

bit 15 SPIEN: SPI1 Enable bit

1 = Enables the module and configures SCK1, SDO1, SDI1 and SS1 as serial port pins

0 = Disables the module

bit 14 Unimplemented: Read as ‘0’

bit 13 SPISIDL: Stop in Idle Mode bit

1 = Discontinue module operation when device enters Idle mode

0 = Cont inue modul e operation in Idle mode

bit 12-7 Unimplemented: Read as ‘0’

bit 6 SPIROV: Receive Overflow Flag bit

1 = A new byte/ word w as completely r eceived and discarded. The user applicati on has not read the

previous data in the SP I1BUF register.

0 = No overflow has occurred

bit 5-2 Unimplemented: Read as ‘0’

bit 1 SPITBF: SPI1 Transmit Buffer Full Status bit

1 = Transmit has not yet started; SPI1TXB is full

0 = Transmit has started; SPI1TXB is empty

Automatically set in hardware when the CPU writes SPI1BUF location, loading SPI1TXB.

Automatically cleared in hardware when the SPI1 module transfers data from SPI1TXB to SPI1SR.

bit 0 SPIRBF: SPI1 Receive Buffer Full Statu s bit

1 = Receive is complete; SPI1RXB is full

0 = Receive is not complete; SPI1RXB is empty

Automatically set in hardware when the SPI1 module transfers data from SPI1SR to SPI1RXB.

Automatically cleared in hardware when the core reads SPI1BUF location, reading SPI1RXB.

Legend: C = Clearable bit

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

Section 35. Serial Peripheral Interface (SPI) (Part II)

Serial Peripheral

Interface (SPI )

Upper Byte:

U-0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

— — — DISSCK DISSDO MODE16 SMP(1) CKE(2)

bit 15 bit 8

Lower Byte:

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

SSEN CKP MSTEN SPRE<2:0> PPRE<1:0>

bit 7 bit 0

bit 15-13 Unimplemented: Read as ‘0’

bit 12 DISSCK: Disable SCK1 Pin bit (SPI Master modes only)

1 = Internal SPI clock is disabled; pin functions as I/O

0 = Internal SPI clock is enabled

bit 11 DISSDO: Disable SDO1 Pin bit

1 = SDO1 pin is not used by the module; pin functions as I/O

0 = SDO1 pin is controlled by the module

bit 10 MODE16: Word/Byte Communication Select bit

1 = Communication is word-wide (16 bits)

0 = Communication is byte-wide (8 bits)

bit 9 SMP: SPI1 Data Input Sample Phase bit(1)

Master mo de:

1 = Input data is sampled at the end of data output time

0 = Input data is sampled at the middle of data output time

Slave mode:

SMP must be cleared when SPI1 is used in Slave mode

bit 8 CKE: SPI1 Clock Edge Select bit(2)

1 = Serial output data changes on transition from active clock state to Idle clock state (see bit 6)

0 = Serial output data changes on transition from Idle clock state to active clock state (see bit 6)

bit 7 SSEN: Slave Select Enab le bit (Slav e mod e)

1 = SS1 pin is used for Slave mode

0 = SS1 pin is not used by module; pin is controlled by port function

bit 6 CKP: Clock Polarity Select bit

1 = Idle state for clock is a high level; active state is a low level

0 = Idle state for clock is a low level; active state is a high level

bit 5 MSTEN: Master Mode Enable bit

1 = Maste r mode

0 = Slave mode

bit 4-2 SPRE<2:0>: Secondary Prescale bits (Master mode)

111 = Second ary prescale 1:1

110 = Second ary prescale 2:1

•

000 = Second ary prescale 8:1

Note 1: The SMP bit must be set only after setting the MSTEN bit. The SMP bit remains cleared if MSTEN = 0.

2: The CKE bit is not used in the Framed SPI modes. The user application should program this bit to ‘0’ for

the Framed SPI modes (FRMEN = 1).

dsPIC30F Family Reference Manual

bit 1-0 PPRE<1:0>: Primary Prescale bits (Master mode)

11 = Primary presc ale 1: 1

10 = Primary presc ale 4: 1

01 = Primary presc ale 16:1

00 = Primary presc ale 64:1

Note 1: SMP bit must be set only after setting the MSTEN bit. The SMP bit remains cleared if MSTEN = 0.

2: The CKE bit is not used in the Framed SPI modes. The user application should program this bit to ‘0’ for

the Framed SPI modes (FRMEN = 1).

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

Section 35. Serial Peripheral Interface (SPI) (Part II)

Serial Peripheral

Interface (SPI )

Upper Byte:

R/W-0 R/W-0 R/W-0 U-0 U-0 U-0 U-0 U-0

FRMEN SPIFSD FRMPOL — — — — —

bit 15 bit 8

Lower Byte:

U-0 U-0 U-0 U-0 U-0 U-0 R/W-0 U-0

— — — — — — FRMDLY —

bit 7 bit 0

bit 15 FRMEN: Framed SPI1 Support bit

1 = Framed SPI1 support is enabled (SS1 pin is used as frame sync pulse input/output)

0 = Framed SPI1 support is disabled

bit 14 SPIFSD: Frame Sync Pulse Direction Control bit

1 = Frame sync pulse input (slave)

0 = Frame sync pul s e out put (m aster)

bit 13 FRMPOL: Frame Sync Pulse Polarity bit

1 = Frame sync pulse is active-high

0 = Frame sync pulse is active-low

bit 12-2 Unimplemented: Read as ‘0’

bit 1 FRMDLY: Frame Sync Pulse Edge Select bit

1 = Frame sync pulse coincides with first bit clock

0 = Frame sync pulse precedes first bit clock

bit 0 Unimplemented: This bit must not be set to ‘1’ by the user applicat ion

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

dsPIC30F Family Reference Manual

35.3 Modes of Operation

The SPI module has flexible operating modes, which are discussed in the following sections:

• 8-bit and 16-bit Data Transmission/Reception

• Master and Slave Modes

• Framed SPI Modes

• SPI1 Receive-only Operation

• SPI1 Error Handling

35.3.1 8-bit and 16-bit Data Transmission/Reception

The MODE16 control bit (SPI1CON1<10>) allows the module to communicate in either 8-bit or

16-bit mo de. Th e functiona lit y will be the same for eac h mode, ex cept fo r the numb er of bit s that

are received and transmitted. Additionally, the following items should be noted in this context:

• The module is reset when the value of the MODE16 bit is changed. Consequently, the bit

should not be changed during normal operation.

• Dat a is trans mitted out of bit 7 of th e SPI1SR regist er for 8-b it operat ion, whil e it is trans mit-

ted out of bit 15 for 16-bit operation. In both modes, data is shifted into bit 0 of the SPI1SR

• When transmitting or receiving data, 8 clock pulses at the SCK1 pin are required to shift

data in or out in 8-bit mode, while 16 clock pulses are required in 16-bit mode.

35.3.2 Master and Slave Modes

Data can be thought of as taking a direct path between the Most Significant bit (MSb) of one

module’s shift register and the Least Significant bit (LSb) of the other, and then into the

appropriate Transmit or Receive Buffer. The module configured as the master module provides

the ser ial clock and sy nchronizati on signals (as required) to the sl ave devic e. Figure 35-2 show s

the connection of the Master and Slave modules.

Figure 35-2 : SPI Ma ster /Sl ave Conn ectio n

Serial Receive Buffer

(SPI1RXB)

Shift Register

(SPI1SR)

LSb

MSb

SDI1

SDO1

PROCESSO R 2 (SP I Slave)

SCK1

SS1(2)

Serial Transmit Buffer

(SPI1TXB)

Serial Receive Buffer

(SPI1RXB)

Shift Register

(SPI1SR)

MSb LSb

SDO1

SDI1

PROCESSOR 1 (SPI Master)

Serial Clock

SSEN (SPI1CON1<7>) = 1 and MS TEN (SPI 1C ON1 <5> ) = 0

Note 1: The user application must write transmit data to and read received data from SPI1BUF. The SPI1TXB and

SPI1RXB registers are memory mapped to SPI1BUF.

2: Using the SS1 pin in the Slave mode of operation is optional.

SS1

SCK1

Serial Transmit Buffer

(SPI1TXB)

MSTEN (SPI1CON1<5 >) = 1

SPI1 Buffer

(SPI1BUF)(1)

SPI1 Buffer

(SPI1BUF)(1)

Section 35. Serial Peripheral Interface (SPI) (Part II)

Serial Peripheral

Interface (SPI )

35.3.2.1 Master Mode

In Maste r m ode, the sys tem cl ock i s presc aled and the n used as the se rial cl ock. T he pres calin g

is based on the settings in the PPRE<1:0> (SPI1CON1<1:0>) and SPRE<2:0>

(SPI1CON1<4:2>) bits. The serial clock is output via the SCK1 pin to the slave devices. The

clock pulses are only generated when there is data to be transmitted. For further information,

refer to 35.4 “Master Mode Clock Frequency”. The CKP and CKE bits determine on which

edge of the clock data transmis si on occ urs .

Both data to be transmitted and data received are, respectively, written into or read from the

SPI1BUF register.

The following describes the SPI1 module operation in Master mode:

1. Once the module is set up for the Master mode of operation and enabled, data to be

transmitted is written to the SPI1BUF register. The SPITBF (SPI1STAT<1>) bit is set.

2. The contents of SPI1TXB are moved to the shift register, SPI1SR, and the SPITBF bit is

cleared by the module.

3. A series of 8/16 clock pulses shifts out 8/16 bits of transmit data from the SPI1SR to the

SDO1 pin and simultaneously shifts in the data at the SDI1 pin into the SPI1SR.

When the transfer is complete, the following events occur:

a) The interrupt flag bit, SPI1IF, is set. SPI1 interrupts can be enabled by setting the

interrupt enable bit, SPI1IE. The SPI1IF flag is not cleared automatically by the

hardware.

b) When the ongoing transmit and receive operation is completed, the contents of the

SPI1SR register are moved to the SPI1RXB register.

c) The SP IRBF (SPI 1STAT<0>) bi t i s set by th e mod ul e, i nd ica tin g that the re cei ve bu f-

fer is full.

d) Once the SPI1BUF register is read by the user application, the hardware clears the

SPIRBF bit.

4. If the SPIR BF bit is set (re ceive buffe r is full) when th e SPI1 module ne eds to transfe r data

from SPI1SR to SPI1 RXB, the modu le will set th e SPIROV (SPI1STAT<6>) bit, indicatin g

an overflow condition.

5. Data to be transmitted can be written to SPI1BU F by the user application at any time as

long as the SPITBF (SPI1STAT<1>) bit is clear. The write can occur while SPI1SR is

shifting out the previously written data, allowing continuous transmission.

Note: The SPI1SR register cannot be written into directly by the user application. All writes

to the SPI1SR register are performed through the SPI1BUF register.

dsPIC30F Family Reference Manual

To set up the SPI1 module for the Master mode of operation, perform the following steps:

1. If using interrupts:

a) Clear the SPI1IF bit in the IFS0 register.

b) Set the SPI1IE bit in the IEC0 register.

c) Write the SPI1IP bits in the IPC2 register to set the interrupt priority.

2. Write the desired settings to the SPI1CON1 register with MSTEN (SPI1CON1<5>) = 1.

3. Clear the SPIROV bit (SPI1STAT<6>).

4. Enable SPI1 module operation by setting the SPIEN bit (SPI1STAT<15>).

5. Write the dat a to be transmitted to the SPI1BUF register . T ransmission (and reception) will

start as soon as data is written to the SPI1BUF register.

Example 35-1 shows a code snip pet for configuring the SPI register for the Master mode.

Example 35-1: SPI Configuration – Master Mode

35.3.2.1.1 External Clocking in Master Mode

In Mas ter mo de, the mo dule can a ls o b e configure d to oper ate with an external data clock. SP I1

clock operation is controlled by the DISSCK bit (SPI1CON1<12>). When this bit is set, the

internal data clock is disabled and data is transferred when external clock pulses are presented

on the SC K1 pi n. Al l ot her aspect s o f Master mode operation are the same as descr ibed above.

/* Following code snippet shows SPI register configuration for MASTER mode*/

IFS0bits.SPI1IF = 0; //Clear the Interrupt Flag

IEC0bits.SPI1IE = 0; //disable the Interrupt

//SPI1CON1 Register Settings

SPI1CON1bits.DISSCK = 0; //Internal Serial Clock is Enabled.

SPI1CON1bits.DISSDO = 0; //SDO1 pin is controlled by the module.

SPI1CON1bits.MODE16 = 1; //Communication is word-wide (16 bits).

SPI1CON1bits.SMP = 0; //Input Data is sampled at the middle of data

//output time.

SPI1CON1bits.CKE = 0; //Serial output data changes on transition from

//Idle clock state to active clock state

SPI1CON1bits.CKP = 0; //Idle state for clock is a low level; active

//state is a high level

SPI1CON1bits.MSTEN = 1; //Master Mode Enabled

SPI1STATbits.SPIEN = 1; //Enable SPI Module

SPI1BUF = 0x0000; //Write data to be transmitted

//Interrupt Controller Settings

IFS0bits.SPI1IF = 0; //Clear the Interrupt Flag

IEC0bits.SPI1IE = 1; //Enable the Interrupt

Note: The DISSCK bit is available only in SPI Master modes.

Section 35. Serial Peripheral Interface (SPI) (Part II)

Serial Peripheral

Interface (SPI )

Figure 35-3: SPI1 Master Mode Timing

SCK1

(CKP = 0

SCK1

(CKP = 1

SCK1

(CKP = 0

SCK1

(CKP = 1

4 Clock

modes

Input

Sample

Input

Sample

SDI1

bit 7 bit 0

SDO1 bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

bit 7

SDI1

SPI1IF

(SMP = 1)(3)

(SMP = 0)(3)

(SMP = 1)(3)

CKE = 1)(2)

CKE = 0)(2)

CKE = 1)(2)

CKE = 0)(2)

(SMP = 0)(3)

User appli cation

SPI1BUF

SDO1 bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

(CKE = 0)

(CKE = 1)

1 instruction cycle latency to set

SPI1IF flag bit

Note 1: If there are no pending transmissions, SPI1TXB is transferred to SPI1SR as soon as the user application writes to

SPI1BUF.

2: Four SPI1 C lock modes ar e shown to demons trate CKP ( SPI1CON1<6>) and CKE (SPI1CON1<8>) bit functionality

only. Only one of the four modes can be chosen for operation.

3: SDI1 and input sample are shown for two different values of the SMP (SPI1CON1<9>) bit for demonstration purposes

only. Only one of the two configurations of the SMP bit can be chosen during operation.

4: Operation for 8-bit mode is shown. Except for the number of clock pulses, the 16-bit mode is similar.

SPI1SR moved

into SPI1RXB

User application

reads SPI1BUF

(clock

output at

the SCK1

pin in

Master

mode)

(SPI1STAT<0>)

SPITBF

SPI1TXB to SPI1SR(1) User application w rites new

data during transmission

SPIRBF

Two modes

available

for SMP

control

bit(4)

bit 0

writes to

dsPIC30F Family Reference Manual

35.3.2. 2 Slave Mode

In Slave mode, data is transmitted and received as the external clock pulses appear on the SCK1

pin. The CKP (SPI1CON<6>) and CKE (SPI1CON<8>) bits determine on which edge of the clock

data tra nsmission occurs. Both dat a to be transm itted and dat a that is receiv ed are, respec tively,

written into or read fro m the SPI1BUF regi ster . The re st of the ope ration of the m odule is id entical

to that described above for the Master mode.

To set up the SPI1 module for the Slave mode of operation, perform the following steps:

1. Clear the SPI1BUF registe r.

2. If using interrupts:

a) Clear the SPI1IF bit in the IFS0 register.

b) Set the SPI1IE bit in the IEC0 register.

c) Write the SPI1IP bits in the IPC2 register to set the interrupt priority.

3. Write the desired settings to the SPI1CON1 and SPI1CON2 registers with MSTEN

(SPI1CON1<5>) = 0.

4. Clear the SMP bit.

5. If the CKE bit is set, then the SSEN bit (SPI1CON1<7 >) must be set to enable the SS1 pin.

6. Clear the SPIROV bit (SPI1STAT<6>).

7. Enable SPI1 operation by setting the SPIEN bit (SPI1STAT<15>).

Example 35-2 shows a code snippet for con figuring the SPI register for the Slave mode.

Example 35-2: SPI Configuration – Slave Mode

35.3.2.2.1 Slave Select Synchronization

The SS1 pin allows the Synchronous Slave mode. If the SSEN (SPI1CON1<7>) bit is set,

transmi ssion a nd rec eptio n are ena bled in Sla ve mode only if t he SS1 pin i s dri ven t o a l ow st ate

(see Figure 35-5). To ensure that the SS1 pin can function correctly as an input, the port output

or other periphe ral outp uts multipl exed wi th the SS1 pin function must not be used. If the SSEN

bit is set and the SS1 pin is driven high, the SDO1 pin is no longer driven and will tri-state even

if the module is in the middle of a transmission.

An aborted transmissi on will be retri ed, using the data held in the SPI1TXB regi ster , the ne xt time

the SS1 pin is driven low. If the SSEN bit is not set, the SS1 pin does not affect the module

operation in Slave mode.

/* Following code snippet shows SPI register configuration for SLAVE mode*/

IFS0bits.SPI1IF = 0; //Clear the Interrupt Flag

IEC0bits.SPI1IE = 0; //Disable The Interrupt

// SPI1CON1 Register Settings

SPI1CON1bits.DISSCK = 0; //Internal Serial Clock is Enabled.

SPI1CON1bits.DISSDO = 0; //SDO1 pin is controlled by the module.

SPI1CON1bits.MODE16 = 1; //Communication is word-wide (16 bits).

SPI1CON1bits.SMP = 0; //Input Data is sampled at the middle of data

//output time.

SPI1CON1bits.CKE = 0; //Serial output data changes on transition

//from Idle clock state to active clock state

SPI1CON1bits.CKP = 0; //Idle state for clock is a low level; active

//state is a high level

SPI1CON1bits.MSTEN = 0; //Master Mode disabled

SPI1STATbits.SPIROV=0; //No Receive Overflow Has Occurred

SPI1STATbits.SPIEN = 1; //Enable SPI Module

//Interrupt Controller Settings

IFS0bits.SPI1IF = 0; //Clear the Interrupt Flag

IEC0bits.SPI1IE = 1; //Enable The Interrupt

Note: To mee t modu l e t imi ng r equ i r em en ts, t he SS 1 pin must be enabled in Slave mode

when CKE = 1 (refer to Figure 35-6 for details).

Section 35. Serial Peripheral Interface (SPI) (Part II)

Serial Peripheral

Interface (SPI )

35.3.2.2.2 SPITBF Status Flag Operation

The SPITBF (SPI1STAT<1>) bit functions differently in the Slave mode of operation than in

Master mode.

If SSEN (SPI1CON1<7>) is c leared , t he SPITBF is set wh en the SPI1BUF is l oad ed by th e us er

application. It is cleared when the module transfers SPI1TXB to SPI1SR. This is similar to the

SPITBF bit function in Master mode.

If SSEN is set, the SPITBF is set when the SPI1B UF is loaded by the user app lication. Howe ver ,

it is cleared only when the SPI1 module completes data transmission. A transmission will be

aborted when the SS1 pin goes high, but may be retried at a later time. Each data word is held

in SPI1TX B until all bits are transmi tted to the receiver.

Figure 35-4: SPI1 Slave Mode Timing (Slave Select Pin Disabled)(1)

SCK1 Input

(CKP = 1

SCK1 Input

(CKP = 0

Input

Sample

SDI1 Input

bit 7 bit 0

SDO1 bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

SPI1IF

(SMP = 0)

CKE = 0)(2)

(SMP = 0)

User application

SPI1BUF(3)

SPI1SR to

SPI1RXB

SPITBF

SPIRBF

Output

Note 1: Operation for 8-bit mode is shown; the 16-bit mode is similar.

2: Two SPI1 Clock modes are shown only to demonstrate CKP (SPI1CON1<6>) and CKE (SPI1CON1<8>) bit

functionality. Any combination of CKP and CKE bits can be selected for module operation.

3: If there are no pending trans missions or a transmission is in progres s, SP I1B UF is tr ansfe rred t o SPI1SR as soon

as the user application writes to SPI1BUF.

1 instruction cycle latency to set

SPI1IF flag bit

writes to

dsPIC30F Family Reference Manual

Figure 35-5: SPI1 Slave Mode Timing (Slave Select Pin Enabled)(1)

SCK1

(CKP = 1

SCK1

(CKP = 0

Input

Sample

SDI1 bit 7 bit 0

SDO1 bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1

SPI1IF

(SMP = 0)

CKE = 0)

(SMP = 0)

SPI1SR to

SPI1BUF

SS1(2)

Note 1: Operat ion for 8-bit mode is shown; the 16-bit mode is similar.

2: When the SSEN (SPI1CON1<7>) bit is set to ‘1’, the SS1 pin must be driven low to enable transmission and

reception in Slave mode.

3: Transmit data is held in SPI1TXB and SPITBF rema ins set until all bits are transmitted.

User application

reads SPI1BUF

SPIRBF

1 instruction

cycle latency

SPITBF(3)

SPI1BUF

SPI1SR

bit 0

User application

writes to SPI1BUF

Section 35. Serial Peripheral Interface (SPI) (Part II)

Serial Peripheral

Interface (SPI )

Figure 35-6: SPI1 Slave Mode Timing (CKE = 1)(1)

35.3.3 Framed SPI Modes

The SPI1 mo dule s upport s a bas ic framed SPI pro tocol while operati ng in eithe r Mas ter or Sl ave

modes. The module uses four control bits to configure framed SPI operation:

• FRMEN (SPI1CON2<15>) enables the Framed SPI modes and causes the SS1 pin to be

used as a frame synchronization pulse input or output pin. The state of SSEN

(SPI1CON1<7>) is ignored.

• SPIFSD (SPI1CON2<14>) determines whether the SS1 pin is an input or an output (i.e.,

whether the module receives or generates the frame synchronization pulse).

• FRMPOL (SPI1CON2<13>) selects the polarity of the frame synchronization pulse

(active-high or active-low) for a single SPI data fram e.

• FRMDLY (SPI1CON2<1>) selects whether the synchronization pulse coincides with or

precedes the first serial clock pulse.

SCK Input

(CKP = 1

SCK Input

(CKP = 0

Input

Sample

SDI Input

bit 7 bit 0

SDO bit 7 bit 6 bi t 5 bit 4 bit 3 bit 2 b i t 1 bit 0

SPI1IF

(SMP = 0)

CKE = 1)

(SMP = 0)

Write to

SPI1BUF SPI1SR to

SPI1RXB

SS1(2,3)

SPITBF(4)

SPIRBF

Output

Note 1: Operat ion for 8-bit mode is shown; the 16-bit mode is similar.

2: The SS1 pin must be used for Slave mode operation when CKE = 1.

3: When the SSEN (SPI1CON1<7>) bit is set to ‘1’, the SS1 pin must be driven low to enable transmission and

reception in Slave mode.

4: Transmit data is held in SPI1TXB and SPITBF rema ins set until all bits are transmitted.

dsPIC30F Family Reference Manual

The SPI1 module supports two framed modes of operation. In Framed Master mode, the SPI1

module generates the frame synchronization pulse and provides this pulse to other devices at

the SS1 pin. In Framed Slave mode, the SPI1 module uses a frame synchronization pulse

received at the SS1 pin.

The following four Framed SPI modes are supported in conjunction with the unframed Master

and Slave modes:

• SPI Master, Frame Master

• SPI Master, Frame Sl ave

• SPI Slave, Frame Maste r

• SPI Slave, Frame Slav e

These modes determine whether or not the SPI1 module generates the serial clock and the

frame synchronization pulse.

When FR MEN ( SPI1C ON 2<1 5>) = 1 an d M STEN (SPI1 CON 1 <5> ) = 1, t he SC K1 pin be co me s

an output and the SPI clock at SCK1 becomes a free running clock.

When FRMEN = 1 and M STEN = 0, the SCK1 pin becomes an input. The source clock provided

to the SCK1 pin is assumed to be a free running clock.

The polarity of the clock is selected by the CKP (SPI1CON1<6>) bit. The CKE (SPI1CON1<8>)

bit is not used for the Framed SPI modes and should be programmed to ‘0’ by the user

application.

When CKP = 0, the frame synchronization pulse output and the SDO1 data output change on

the rising edge of the clock pulses at the SCK1 pin. Input data is sampled at the SDI1 input pin

on the falling edge of the serial clock.

When CKP = 1, the frame synchronization pulse output and the SDO1 data output change on

the falling edge of the clock pulses at the SCK1 pin. Input data is sampled at the SDI1 input pin

on the rising edge of the serial clock.

35.3.3.1 Frame Master and Frame Slave Modes

When SPIFSD (SPI1CON2<14>) = 0, the SPI1 module is in the Frame Master mode of

operat ion. In this mo de, the frame sy nc pulse is init iated by the mo dule when the us er applicat ion

writes the transmit dat a to the SPI1BUF loc ation (thus writ ing the SPI1TXB register w ith transmit

data). At the end of the frame synchronization pulse, the SPI1TXB is transferred to the SPI1SR

and data transmission or reception begins.

When SPIFSD = 1, the module is in Framed Slave mode. In this mode, the frame synchronization

pulse is generated by an external source. When the module samples the frame synchronization

pulse, it will transfer the contents of the SPI1TXB register to the SPI1SR and data transmission

or reception begins. The user application must make sure that the correct transmission data is

loaded into the SPI1BUF before the frame synchronization pulse is received.

Note: The use of the SS1 and SCK1 pins is mandatory in all Framed SPI modes.

Note: Receiving a frame synchronization pulse will start a transmission regardless of

whether data was written to SPI1BUF. If no write was performed, the old contents of

the SPI1TXB will be transmitted.

Section 35. Serial Peripheral Interface (SPI) (Part II)

Serial Peripheral

Interface (SPI )

35.3.3.2 SPI Master, Frame Master Mode

In the SPI Master/Frame Master mode, the SPI1 module generates both the clock and frame

synchronization signals, as shown in Figure 35-7. This configuration is enabled by setting the

MSTEN and FRMEN bits to ‘1’ and the SPIFSD bit to ‘0’.

In this mode, the serial clock is output continuously at the SCK1 pin regardless of whether the

module is transmitti ng. When SPI1 BUF is written, the SS1 pi n will be dr iven to its activ e sta te (as

determined by the FRMPOL bit) on the appropriate transmit edge of the SCK1 clock and remain

active for one data frame. If the FRMDLY control bit (SPI1CON2<1>) is cleared, the frame

synchronization pulse precedes the data transmission, as shown in Figure 35-8. If FRMDLY is

set, the frame synchronization pulse coincides with the beginning of the data transmission, as

shown in Figure 35-9. The module st arts transmitting dat a on the next tran smit edge of the SCK1.

Figure 35-7: SPI Master, Frame Master Connection Diagram

Figure 35-8: SPI Master, Frame Master Timing (FRMDLY = 0)

Figure 35-9: SPI Master, Frame Master Timing (FRMDLY = 1)

SDO1

SDI1

dsPIC30F

Serial Clock

SS1

SCK1

Frame Synchronization

Pulse

SDI1

SDO1

PROC ESSOR 2

SS1

SCK1

(SPI1 Master, Framed Master)

SCK1

SS1

SDO1

(CKP = 0)

bit 14 bit 13 bit 12

SDI1

bit 14 bit 13 bit 12

Write to SPI1BUF Receive Samples at SDI1

Pulse Generated at SS1

SCK1

(CKP = 1)

(FRMPOL = 1)

SS1

(FRMPOL = 0)

bit 15

SCK1

SDO1

(CKP = 0)

bit 14 bit 13 bit 12

SDI1 bit 14 bit 13 bit 12

Write to SPI1BUF Pulse Generated by SS1;

SCK1

(CKP = 1)

SS1

(FRMPOL = 1)

SS1

(FRMPOL = 0)

Receive Samples at SDI1

bit 15

dsPIC30F Family Reference Manual

35.3.3.3 SPI Master, Frame Slave Mode

In the SPI Master/Frame Sl av e m od e, the module gen erates the c loc k si gn al but us es th e Sl av e

module fram e synchro nization s ignal for da ta transm ission (F igure 35-10). Th is mode is enabled

by setting the MSTEN, FRMEN and SPIFSD bits to ‘1’.

In this mo de, the SS1 pin is an inp ut and is sampl ed on the sample edg e of the SPI1 clock. Whe n

it is sampled in its active state, data will be transmitted on the subsequent transmit edge of the

SPI1 clock. The interrupt flag, SPI1IF, is set when the transmission is complete. The user

applic ation mus t make sure that the c orrect trans missio n data is loaded into the SP I1BUF befo re

the signal is received at the SS1 pin.

Figure 35-10: SPI Master, Frame Slave Connection Diagram

Figure 35-11: SPI Master, Frame Slave T im ing (FRMD LY = 0)

Figure 35-1 2: SPI Master, Frame Slave Timing (FRMDLY = 1)

SDO1

SDI1

dsPIC30F

Serial Clock

SS1

SCK1

Frame Synchronization

Pulse

SDI1

SDO1

PROC ES SO R 2

SS1

SCK1

(SPI1 Master, Framed Slave)

SCK1

SDO1

(CKP = 0)

bit 14 bit 13 bit 12

SDI1

Sample SS1 pin for Pulse Receive Samples at SDI1

bit 14 bit 13 bit 12

Write to SPI1BUF

SCK1

(CKP = 1)

SS1

(FRMPOL = 1)

SS1

(FRMPOL = 0)

bit 15

SCK1

SDO1

(CKP = 0)

bit 14 bit 13 bit 12

SDI1 bit 14 bit 13 bit 12

SCK1

(CKP = 1)

Write to SPI1BUF Pulse Generated by SS1;

Receive Samples at SDI1

SS1

(FRMPOL = 1)

SS1

(FRMPOL = 0)

bit 15

Section 35. Serial Peripheral Interface (SPI) (Part II)

Serial Peripheral

Interface (SPI )

35.3.3.4 SPI Slave, Frame Master Mode

In the SPI Slave/Frame Mas te r mo de, the m od ul e ac t s as the SPI slave an d t akes its clock from

the other SPI module; however, it produces frame synchronization signals to control data

transmission (Figure 35-13). This mode is enabled by setting the MSTEN bit to ‘0’, the FRMEN

bit to ‘1’ and the SPIFSD bit to ‘0’.

The input SPI clock will be continuous in Slave mode. The SS1 pin will be an output when the

SPIFSD bi t is lo w. Therefore , when th e SPI1BU F is wri tten, th e module drive s the S S1 pin to the

active state on the appropriate transmit edge of the SPI clock for one SPI clock cycle. Data will

start transmitting on the appropriate SPI clock transmit edge.

Figure 35-13: SPI Slave, Frame Master Connection Diagram

35.3.3.5 SPI Slave, Frame Slave Mode

In the SPI Slave/Frame Slave mode, the modu le obtains bot h its clock an d frame synchronization

signal from the Master module (Figure 35-14). This mode is enabled by setting MSTEN to ‘0’,

FRMEN to ‘1’ and SPIFSD to ‘1’.

In this m od e, both t he SC K1 and SS1 pi ns wi ll be input s. The SS1 pin is s am pl ed on th e s am pl e

edge of the SPI clock. When SS1 is sampled at its active state, data will be transmitted on the

appropriate transmit edge of SCK1.

Figure 35-14: SPI Slave, Frame Slave Connection Diagram

SDO1

SDI1

dsPIC30F

Serial Clock

SS1

SCK1

Frame Synchronization

Pulse

SDI1

SDO1

PROCESSOR 2

SS1

SCK1

(SPI1 Slave, Framed Ma ster)

SDO1

SDI1

dsPIC30F

Serial Clock

SS1

SCK1

Frame Synchronization

Pulse

SDI1

SDO1

PROC ES SOR 2

SS1

SCK1

(SPI1 Slave, Framed Slave)

dsPIC30F Family Reference Manual

35.3.4 SPI1 Receive- onl y Operat ion

Setting the DISSDO control bit (SPI1CON1<11>) disables transmission at the SDO1 pin. This

allows the SPI1 module to be configured for a Receive-only mode of operation. The SDO1 pin

will be controlled by the respective port function if the DISSDO bit is set.

The DISSDO function is applicable to all SPI operating modes.

35.3.5 SPI1 Error Han dlin g

If a new data word has been shifted into SPI1SR but the previous SPI1BUF contents have not

been read, the SPIROV bit (SPI1STAT<6>) will be set. Any received data in SPI1SR will not be

transferred, and further data reception is disabled until the SPIROV bit is cleared. The SPIROV

bit is not cleared automatically by the module; it must be cleared by the user application.

The SPI1 Interrupt Flag, SPI1IF, is set whenever the SPIROV, SPIRBF (SPI1STAT<0>) or

SPITBF (SPI1 STA T< 1>) bit s are set. Th e interr upt flag canno t be cl eared b y hardwa re and m ust

be reset i n software . The actual SPI1 interr upt is generate d only wh en the correspo nding SPI1IE

bit is set in the IEC0 Control register.

Section 35. Serial Peripheral Interface (SPI) (Part II)

Serial Peripheral

Interface (SPI )

35.4 Master Mode Clock Frequency

In the Master mode, the clock provided to the SPI1 module is the instruction cycle (TCY). This

clock will then be prescaled by the primary prescaler, specified by PPRE<1:0>

(SPI1CON1<1:0>), and the secondary prescaler, specified by SPRE<2:0> (SPI1CON1<4:2>).

The prescaled instruction clock becomes the serial clock and is provided to external devices

through the SCK1 pin.

Equation 35-1 can be used to calculate the SCK1 clock frequency as a function of the primary

and secondary prescaler settings.

Equation 35-1: SPI Clock Frequency

Some sample SPI clock frequencies (in kHz) are shown in Table 35-1.

Table 35-1: Sample SCK1 Frequencies(1)

Note: Note t hat the SCK1 sign al clock is no t free running fo r normal SPI modes . It will only

run for 8 or 16 pulses when the SPI1BUF is loaded with data. However, it is

continuous for Framed modes.

Note: Not all clock rates are supported. For further information, refer to the SPI module

timing specifications in the specific device data sheet.

Primary Pr escaler * Second ary Prescaler

FCY

FSCK =

FCY = 30 MHz Secondary Prescaler Settings

1:1 2:1 4:1 6:1 8:1

Primary Prescaler Settings 1:1 30000 15000 7500 5000 3750

4:1 7500 3750 1875 1250 938

16:1 1875 938 469 313 234

64:1 469 234 117 78 59

FCY = 5 MHz

Primary Prescaler Settings 1:1 5000 2500 1250 833 625

4:1 1250 625 313 208 156

16:1 313 156 78 52 39

64:1 78 39 20 13 10

Note 1: SCK1 frequencies are shown in kHz.

dsPIC30F Family Reference Manual

35.5 Operation in Power-Saving Modes

The dsPIC30F SMPS and Digital Power Conversion device family has three power modes: the

normal o peratio nal (Ful l-Powe r) mode a nd the tw o powe r-savin g mode s inv oked by the PWRSAV

instruc tion. Dependi ng on the SPI mode selec ted, enterin g a power-saving m ode may also af fect

the operation of the SPI1 module.

35.5.1 Sleep Mode

When the device enters Sleep mode, the system clock is disabled. The consequences of

entering Sleep mode depend on which mode (Master or Slave) the SPI1 module is configured

for at the time that Sleep mode is invoked.

35.5.1.1 Master Mode Operation

The consequences of entering Sleep mode when the SPI1 module is configured for Master

operation are as follows:

• The Baud Rate Ge nera tor in the SPI1 mod ule stop s and is reset.

• The transmitter and receiver will stop in Sleep mode. The transmitter or receiver does not

continue with a partially completed transmission at wake-up.

• If the SPI1 module enters Sleep mode in the middle of a transmission or reception, the

transmission or reception is aborted. Since there is no automatic way to prevent an entry

into Sleep mode if a transmission or reception is pending, the user application must

synchronize entry into Sleep mode with SPI1 module operation to avoid aborted

transmissions.

35.5.1.2 Slav e Mode Operation

Since the cl ock pulse s at SCK1 are extern ally provided for Sla ve mode, the mo dule will cont inue

to functi on in Sleep mode . It will complete an y transaction s during the transi tion into Sleep m ode.

On completion of a transaction, the SPIRBF flag is set. Consequently, the SPI1IF bit will be set.

If SPI1 interrupts are enabled (SPI1IE = 1), the device will wake from Sleep mode. If the SPI1

interrupt priority level is greater than the present CPU priority level, code execution will resume

at the SPI1 interrupt vec tor loc at ion . O the rwis e, c od e e xec ut ion w ill c ont inu e with the ins truc tio n

following the PWRSAV instruction that previously invoked Sleep mode. The module is not Reset

on entering Sleep mode if it is operating as a slave device.

The regist er content s are not affect ed when the SPI1 module is going into or co ming out of Sleep

mode.

35.5.2 Idle Mod e

When the dev ice enters Idle mode, the system clock so urces rema in function al. The SPISIDL bit

(SPI1STAT<13>) selects whether the module will stop or continue functioning on Idle mode.

If SPISIDL = 1, the S PI1 modu le wi ll s top comm uni catio n on ent eri ng Id le m ode. It w ill oper ate

in the same m ann er as it does i n Sl eep m od e. If SPISIDL = 0 (de fault se lect ion), the module will

continue operation in Idle mode.

Section 35. Serial Periph eral Interface (SPI) (Part II)

ial Pe

iphe

Inte rface (SPI)

35.6 Special Function Registers Associated with the SPI1 Module

Table 35-2: SPI1 Register Map

SFR Name Addr. Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 All Resets

SPI1STAT 0240 SPIEN — SPISIDL — — — — — —SPIROV — — — — SPITBF SPIRBF 0000

SPI1CON1 0242 — — — DISSCK DISSDO MODE16 SMP CKE SSEN CKP MSTEN SPRE<2:0> PPRE<1:0> 0000

SPI1CON2 0244 FRMEN SPIFSD FRMPOL — — — — — — — — — — — FRMDLY —0000

SPI1BUF 0246 SPI1 Transmit and Receive Buffer Register 0000

dsPIC30F Family Reference Manual

35.7 Related Application Notes

This section lists application notes that are related to this section of the manual. These

application notes may not be written specifically for the dsPIC30F SMPS and Digital Power

Conversion device family, but the concepts are pertinent and could be used with modification and

possib le lim ita tions. The current a pplic ation n otes relate d to the Se rial Perip heral In terf ace (SPI)

module inc lude the following:

Title Application Note #

Interfacing SPI™ Serial EEPROMs to PIC18 Devices AN1006

Interfacing Microchip’s MCP41XXX and MCP42XXX Digital Potentiometers

to a PICmicro® Microcontroller AN746

Interfacing Microchip’s MCP3201 Analog-to-Digital Converter to the

PICmicro® Microcontroller AN719

Note: Please visit the Microchip web site (www.microchip.com) for additional application

notes and code examples for the dsPIC30F SMPS and Digital Power Conversion

device f amily.

Section 35. Serial Peripheral Interface (SPI) (Part II)

Serial Peripheral

Interface (SPI )

35.8 Revision History

Revision A (February 2007)

This is the initial released revision of this document.

Revision B (September 2008)

This revision incorporates the following content updates:

•Registers:

- SPI 1CON1: SPI1 Control Register 1 (s ee Register 35-2) – Note 1 has been a dded in

the register.

• Additional minor corrections such as language and formatting updates are incorporated in

the entire document.

dsPIC30F Family Reference Manual

NOTES: