71M6541DT/71M6541FT/71M6541GT/
71M6542FT/71M6542GT
Energy Meter ICs
General Description
The 71M6541DT/71M6541FT/71M6541GT/71M6542FT/
71M6542GT (71M654xT) are 4th-generation single-
phase metering systems-on-chips (SoCs) with a 5MHz,
8051-compatible MPU core, low-power RTC with digital
temperature compensation, flash memory, and LCD driver.
Our Single Converter Technology® with a 22-bit delta-
sigma ADC, three or four analog inputs, digital temperature
compensation, precision voltage reference, and a 32-bit
computation engine (CE) support a wide range of metering
applications with very few external components.
The 71M654xT devices support optional interfaces to the
Maxim Integrated 71M6x01 series of isolated sensors
offering BOM cost reduction, immunity to magnetic tam-
per, and enhanced reliability. Other features include an
SPI interface, advanced power management, ultra-low-
power operation in active and battery modes, 3KB/5KB
shared RAM, and 32KB/64KB/128KB flash memory that
can be programmed in the field with code and/or data
during meter operation and the ability to drive up to six
LCD segments per SEG driver pin. High processing and
sampling rates combined with differential inputs offer a
powerful platform for residential meters.
A complete array of code development tools, demonstra-
tion code, and reference designs enable rapid develop-
ment and certification of meters that meet all ANSI and
IEC electricity metering standards worldwide.
The 71M654xT family operates over the industrial tempera-
ture range and comes in 64-pin (71M6541DT/FT/GT) and
100-pin (71M6542FT/GT) lead(Pb)-free LQFP packages.
Applications
● Single-PhaseResidential,Commercial,andIndustrial
Energy Meters
Benets and Features
● SoCIntegrationandUniqueIsolationTechnique
Reduces BOM Cost Without Sacrificing Performance
• 0.1% Typical Accuracy Over 2000:1 Current
Range
• Exceeds IEC 62053/ANSI C12.20 Standards
• Four-Quadrant Metering
• 46-64HzLineFrequencyRangewiththeSame
Calibration
• Phase Compensation (±10º)
• Independent 32-Bit Compute Engine
• 32KB Flash, 3KB RAM (71M6541DT)
• 64KB Flash, 5KB RAM (71M6541FT/71M6542FT)
• 128KB Flash, 5KB RAM (71M6541GT/71M6542GT)
• Built-In Flash Security
• Up to Four Pulse Outputs with Pulse Count
• 8-Bit MPU (80515), Up to 5 MIPS
• Full-Speed MPU Clock in Brownout Mode
• LCD Driver Allows Up to 6 Commons/Up to
56 Pins
• Up to 51 Multifunction DIO Pins
• Hardware Watchdog Timer (WDT)
• Two UARTs for IR and AMR
• IR LED Driver with Modulation
● InnovativeIsolationTechnology(Requires
Companion 71M6xxx Sensor, also from Maxim
Integrated) Eliminates Current Transformers
• Two Current Sensor Inputs with Selectable
Differential Mode
• Selectable Gain of 1 or 8 for One Current Input to
Support Shunts
• High-Speed Wh/VARh Pulse Outputs with
Programmable Width
● DigitalTemperatureCompensationImprovesSystem
Performance
• Metrology Compensation
• Accurate RTC for TOU Functions with Automatic
Temperature Compensation for Crystal in All
Power Modes
● PowerManagementExtendsBatteryLifeDuring
Power Outages
• Three Battery-Backup Modes
- Brownout Mode (BRN)
- LCD Mode (LCD)
- Sleep Mode (SLP)
• Wake-Up on Pin Events and Wake-On Timer
• 1µA in Sleep Mode
19-6547; Rev 6; 12/15
Ordering Information and Typical Operating Circuit appear
at end of data sheet.
Single Converter Technology is a registered trademark of
Maxim Integrated Products, Inc.
EVALUATION KIT AVAILABLE
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TABLE OF CONTENTS
General Description ............................................................................ 1
Applications .................................................................................. 1
Benefits and Features .......................................................................... 1
Absolute Maximum Ratings ...................................................................... 7
Electrical Characteristics ........................................................................ 7
Recommended External Components............................................................. 12
Pin Configurations ............................................................................ 13
Pin Descriptions .............................................................................. 15
Block Diagram ............................................................................... 18
I/OEquivalentCircuits ......................................................................... 19
Hardware Description.......................................................................... 20
Analog Front-End (AFE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Signal Input Pins .........................................................................23
Input Multiplexer..........................................................................23
Delay Compensation ......................................................................24
ADC Preamplifier .........................................................................25
Analog-to-Digital Converter (ADC) ...........................................................25
FIR Filter ...............................................................................25
Voltage References .......................................................................25
Isolated Sensor Interface...................................................................25
Digital Computation Engine (CE) ...............................................................26
MeterEquations..........................................................................26
Real-Time Monitor ........................................................................26
Pulse Generators .........................................................................26
XPULSE and YPULSE.....................................................................27
VPULSE and WPULSE ....................................................................27
80515 MPU Core............................................................................27
Memory Organization and Addressing ........................................................27
Program Memory .........................................................................27
MPU External Data Memory (XRAM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
MOVX Addressing ........................................................................28
Dual Data Pointer.........................................................................28
Internal Data Memory Map and Access .......................................................29
Special Function Registers .................................................................29
Timers and Counters ......................................................................29
Interrupts ...............................................................................31
Interrupt Overview ........................................................................31
External MPU Interrupts ...................................................................32
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TABLE OF CONTENTS (continued)
On-Chip Resources .........................................................................32
Flash Memory ...........................................................................32
MPU/CE RAM ...........................................................................33
I/O RAM ................................................................................33
Crystal Oscillator .........................................................................33
PLL ....................................................................................33
Real-Time Clock (RTC) ....................................................................33
RTC Trimming ...........................................................................33
RTC Interrupts ...........................................................................34
Temperature Sensor ......................................................................34
Battery Monitor...........................................................................34
Digital I/O and LCD Segment Drivers .........................................................35
LCD Drivers .............................................................................35
SquareWaveOutput ......................................................................36
EEPROM Interface .......................................................................36
Two-Pin EEPROM Interface ................................................................36
Three-Wire EEPROM Interface ..............................................................36
UART ..................................................................................36
SPI Slave Port ...........................................................................37
SPI Safe Mode...........................................................................37
SPI Flash Mode (SFM).....................................................................38
Hardware Watchdog Timer .................................................................38
Test Ports ...............................................................................38
Functional Description ......................................................................... 40
Theory of Operation .........................................................................40
Battery Modes..............................................................................40
Brownout Mode ..........................................................................41
LCD Only Mode ..........................................................................41
Sleep Mode .............................................................................41
Applications Information........................................................................ 42
Connecting 5V Devices ......................................................................42
Direct Connection of Sensors..................................................................42
Using the 71M6541DT/FT/GT with Local Sensors ..................................................42
Using the 71M6541DT/FT/GT with Remote Sensors ................................................42
Using the 71M6542FT/GT with Local Sensors .....................................................42
Using the 71M6542FT/GT with Remote Sensors ...................................................42
Metrology Temperature Compensation ..........................................................42
Connecting I2C EEPROMs....................................................................42
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TABLE OF CONTENTS (continued)
Connecting Three-Wire EEPROMs .............................................................42
UART0....................................................................................48
Optical Interface ............................................................................48
Reset .....................................................................................49
MPU Firmware Library .......................................................................49
Reading the Info Page .......................................................................65
Meter Calibration............................................................................66
Firmware Interface ............................................................................ 66
Overview: Functional Order ...................................................................66
I/O RAM Map: Details ........................................................................66
CE Interface Description......................................................................66
CE Program .............................................................................66
CE Data Format ..........................................................................66
Constants ...............................................................................67
Environment .............................................................................67
CE Calculations ..........................................................................68
CE Input Data ...........................................................................68
CE Status and Control .....................................................................68
Transfer Variables ........................................................................68
Pulse Generation .........................................................................68
CE Flow Diagrams ............................................................................ 68
Ordering Information .......................................................................... 75
Package Information .......................................................................... 75
Typical Operating Circuit ....................................................................... 76
Revision History .............................................................................. 77
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LIST OF FIGURES
Figure1.I/OEquivalentCircuits ................................................................. 19
Figure 2. 71M6541DT/FT/GT Operating with Local Sensors ............................................ 21
Figure 3. 71M6541DT/FT/GT Operating with Remote Sensor for Neutral Current ........................... 21
Figure 4. 71M6542FT/GT Operating with Local Sensors .............................................. 22
Figure 5. 71M6542FT/GT Operating with Remote Sensor for Neutral Current .............................. 22
Figure6.MultiplexerSequencewithMUX_DIV=3 .................................................. 24
Figure7.MultiplexerSequencewithMUX_DIV=4 .................................................. 24
Figure 8. Typical LCD Waveforms ................................................................ 34
Figure 9. Optical Interface (UART1)............................................................... 37
Figure 10. Waveforms Comparing Voltage, Current, Energy per Interval, and Accumulated Energy............. 40
Figure 11. Typical Voltage Sense Circuit Using Resistive Divider ........................................ 43
Figure 12. Typical Current-Sense Circuit Using Current Transformer in a Single-Ended Configuration .......... 43
Figure 13. Typical Current-Sense Circuit Using Current Transformer in a Differential Configuration............. 43
Figure 14. Typical Current-Sense Circuit Using Shunt in a Differential Configuration ........................ 43
Figure 15. 71M6541DT/FT/GT Typical Operating Circuit Using Locally Connected Sensors ................... 44
Figure 16. 71M6541DT/FT/GT Typical Operating Circuit Using Remote Neutral Current Sensor................ 45
Figure 17. 71M6542FT/GT Typical Operating Circuit Using Local Sensors ................................ 46
Figure 18. 71M6542FT/GT Typical Operating Circuit Using Remote Neutral Current Sensor .................. 47
Figure 19. Typical I2C Operating Circuit ........................................................... 48
Figure 20. Typical UART Operating Circuit ......................................................... 48
Figure 21. Optical Interface Typical Operating Circuit ................................................. 48
Figure 22. Typical Reset Circuits ................................................................. 49
Figure 23. Typical Emulator Connections .......................................................... 49
Figure 24. CE Data Flow—Multiplexer and ADC..................................................... 73
Figure 25. CE Data Flow—Offset, Gain, and Phase Compensation ......................................74
Figure 26. CE Data Flow—SquaringandSummation..................................................74
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LIST OF TABLES
Table 1. ADC Input Configuration ................................................................ 25
Table 2. Inputs Selected in Multiplexer Cycles ...................................................... 27
Table3.CKMPUClockFrequencies .............................................................. 27
Table 4. Memory Map ......................................................................... 28
Table 5. Internal Data Memory Map .............................................................. 29
Table 6. Special Function Register Map ........................................................... 29
Table 7. Generic 80515 SFRs: Location and Reset Values............................................. 30
Table 8. Timers/Counters Mode Description ........................................................ 31
Table 9. External MPU Interrupts................................................................. 32
Table 10. Flash Banks ......................................................................... 32
Table 11. Test Ports ........................................................................... 38
Table 12. I/O RAM Locations in Numerical Order .................................................... 50
Table 13. I/O RAM Locations in Alphabetical Order .................................................. 55
Table 14. Info Page Trim Fuses .................................................................. 65
Table15.PowerEquations...................................................................... 67
Table 16. CE Raw Data Access Locations ......................................................... 67
Table 17. CE Status Register .................................................................... 69
Table 18. CE Configuration Register .............................................................. 69
Table 19. Sag Threshold and Gain Adjustment Registers.............................................. 70
Table 20. CE Transfer Registers ................................................................. 70
Table 21. CE Pulse Generation Parameters ........................................................ 71
Table 22. Other CE Parameters.................................................................. 72
Table 23. CE Calibration Parameters ............................................................. 73
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(All voltages referenced to GNDA.)
Supplies and Ground Pins
VV3P3SYS, VV3P3A ............................................... -0.5V to +4.6V
VBAT, VBAT_RTC...................................................-0.5V to +4.6V
GNDD ...................................................................-0.1V to +0.1V
Analog Output Pins
VREF .......................-10mA to +10mA, -0.5V to (VV3P3A + 0.5V)
VDD ..........................................-10mA to +10mA, -0.5V to +3.0V
VV3P3D ....................................-10mA to +10mA, -0.5V to +4.6V
VLCD ........................................-10mA to +10mA, -0.5V to +6.0V
Analog Input Pins
IAP, IAN, VA, IBP, IBN, VB* ................-10mA to +10mA, -0.5V to
(VV3P3A + 0.5V)
XIN, XOUT...............................-10mA to +10mA, -0.5V to +3.0V
SEG and SEGDIO Pins
Configured as SEG or COM Drivers . -1mA to +1mA, -0.5V to +6.0V
Configured as Digital Inputs ....-10mA to +10mA, -0.5V to +6.0V
Configured as Digital Outputs ............-10mA to +10mA, -0.5V to
(VV3P3D + 0.5V)
Digital Pins
Inputs(PB,RESET,RX,ICE_E,TEST) ...........-10mA to +10mA,
-0.5V to +6.0V
Outputs (TX) .......... -10mA to +10mA, -0.5V to (VV3P3D + 0.5V)
Temperature
Operating Junction Temperature (peak, 100ms) ............. +140°C
Operating Junction Temperature (continuous) ................ +125°C
Storage Temperature ........................................ -45°C to +140°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) ....................................... +260°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Absolute Maximum Ratings
*71M6542FT/GT only.
Electrical Characteristics
(Limits are production tested at TA=+25°C.Limitsovertheoperatingtemperaturerangeandreleventsupplyvoltagerangeareguaran-
teed by design and characterization.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
RECOMMENDED OPERATING CONDITIONS
VV3P3SYS and VV3P3A Supply
Voltage Precision metering operation 3.0 3.6 V
VBAT
PLL_FAST=1 2.65 3.8 V
PLL_FAST=0 2.40 3.8
VBAT_RTC 2.0 3.8 V
Operating Temperature -40 +85 °C
INPUT LOGIC LEVELS
Digital High-Level Input Voltage
(VIH)2 V
Digital Low-Level Input Voltage
(VIL)0.8 V
Input Pullup Current, (IIL) E_
RTXT,E_RST,E_TCLK 10 100 µA
Input Pullup Current, (IIL)OPT_
RX,OPT_TX 10 100 µA
Input Pullup Current, (IIL)SPI_
CSZ (SEGDIO36) 10 100 µA
Input Pullup Current, (IIL) Other
Digital Inputs -1 +1 µA
Input Pulldown Current (IIH),
ICE_E,RESET,TEST 10 100 µA
Input Pulldown Current, (IIH)
Other Digital Inputs -1 +1 µA
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Electrical Characteristics (continued)
(Limits are production tested at TA=+25°C.Limitsovertheoperatingtemperaturerangeandreleventsupplyvoltagerangeareguaran-
teed by design and characterization.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
OUTPUT LOGIC LEVELS
Digital High-Level Output
Voltage (VOH)
ILOAD=1mA VV3P3D
- 0.4 V
ILOAD=15mA(Note1) VV3P3D
- 0.8 V
Digital Low-Level Output
Voltage (VOL)
ILOAD=1mA 0 0.4 V
ILOAD=15mA(Note1) 0 0.8 V
BATTERY MONITOR
BatteryVoltageEquation:3.3+(BSENSE-BNOM3P3)x0.0252+STEMPx2.79E-5V
Measurement Error
VBAT=2.0V -3.5 +3.5
%
VBAT=2.5V -3.5 +3.5
VBAT=3.0V -3.0 +3.0
VBAT=3.8V -3.0 +3.0
Input Impedance 260 kΩ
Passivation Current IBAT(BCURR=1)-IBAT(BCURR=0) 50 100 165 µA
TEMPERATURE MONITOR
Temperature Measurement
Equation
22.15 + STEMP x 0.085
- 0.0023 x STEMP x
[(STEMPT85P -STEMPT22P)
/(T85P - T22P) - 12.857]
°C
Temperature Error (Note 1)
TA=+85°C -3.2 +3.2
°C
TA=0°Cto+70°C -2.65 +2.65
TA=-20°C -3.4 +3.4
TA=-40°C -3.8 +3.8
VBAT_RTC Charge per
Measurement 2 µC
Duration of Temperature
MeasurementafterTEMP_
START
22 40 ms
SUPPLY CURRENT
VV3P3A + VV3P3SYS Supply
Current (Note 1)
VV3P3A=VV3P3SYS=3.3V;MPU_DIV=3(614kHz
MPUclock);PLL_FAST=1;PRE_E=0 5.5 6.7
mA
PLL_FAST=0 2.6 3.5
PRE_E=1 5.7 6.9
PLL_FAST=0,PRE_E=1 2.6 3.6
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Electrical Characteristics (continued)
(Limits are production tested at TA=+25°C.Limitsovertheoperatingtemperaturerangeandreleventsupplyvoltagerangeareguaran-
teed by design and characterization.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Dynamic Current 0.4 0.6 mA/MHz
VBAT Current
Mission mode -300 +300 nA
Brownout mode 2.4 3.2 mA
LCD mode (external VLCD) 0.4 108 nA
LCD mode (internal VLCD from DAC) 3.0 16 µA
LCD mode (VBAT) 1.4 3.8 µA
Sleep mode -300 +300 nA
VBAT_RTC Current
Brownout mode 400 650 nA
LCD mode 1.8 4.1 µA
Sleep mode, TA≤25°C 0.7 1.7 µA
Sleep mode, TA=85°C(Note1) 1.5 3.2 µA
Flash Write Current Maximumashwriterate 7.1 9.3 mA
VV3P3D SWITCH
On-Resistance VV3P3SYS to VV3P3D, IV3P3D≤1mA 11 Ω
VBAT to VV3P3D, IV3P3D≤1mA 11
IOH 9 mA
INTERNAL POWER FAULT COMPARATOR
Response Time 100mV overdrive, falling 20 200 µs
100mV overdrive, rising 200
Falling Threshold, 3.0V
Comparator 2.83 2.93 3.03 V
Falling Threshold, 2.8V
Comparator 2.71 2.81 2.91 V
Difference between 3.0V and
2.8V comparators 47 136 220 mV
Falling Threshold, 2.25V
Comparator 2.14 2.33 2.51 V
Falling Threshold, 2.0V
Comparator 1.90 2.07 2.23 V
Difference between 2.25V and
2.0V Comparators 0.15 0.25 0.365 V
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Electrical Characteristics (continued)
(Limits are production tested at TA=+25°C.Limitsovertheoperatingtemperaturerangeandreleventsupplyvoltagerangeareguaran-
teed by design and characterization.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Hysteresis TA=+22°C
3.0V comparator 13 45 81
mV
2.8V comparator 17 42 79
2.25V comparator 7 33 71
2.0V comparator 4 28 83
2.5V REGULATOR
VV2P5 Output Voltage VV3P3=3.0Vto3.8V,ILOAD=0mA 2.55 2.65 2.75 V
VV2P5 Load Regulation VBAT=3.3V,VV3P3=0V,ILOAD=0mAto1mA 40 mV
Dropout Voltage ILOAD=5mA 440 mV
ILOAD=0mA 200
PSSR ILOAD=0mA 5 mV/V
CRYSTAL OSCILLATOR
Maximum Output Power to
Crystal 1 µW
Adjustment Range, XOUT
Capacitance RTCA_ADJ=0x7Fto0x00 15 pF
PLL
PLL Settling Time
Power-up 3
ms
PLL_FASTtransition,lowtohigh 3
PLL_FASTtransition,hightolow 3
Mode transition, sleep to mission 3
LCD
VLCD Current
VLCD=3.3V,LCD_CLK=0b11,allsegmentson 8.1
µA
VLCD=3.3V,LCD_CLK=0b10,allsegmentson 4.6
VLCD=3.3V,allsegmentsoff 2.1
VLCD=5.0V,LCD_CLK=0b11,allsegmentson 12.0
VLCD=5.0V,LCD_CLK=0b10,allsegmentson 4.6
VLCD=5.0V,allsegmentsoff 3.0
VREF
VREF Output Voltage TA=+22°C 1.193 1.195 1.197 V
VREF Output Impedance ILOAD=-10µAto+10µA 3.2 kΩ
VREF Power Supply Sensitivity VV3P3A=3.0Vto3.6V -1.5 +1.5 mV/V
VREF Temperature Sensitivity
(Note 1)
VREFT=VREF22 + (T-22)TC1
+ (T-22)2TC2
V
TC1=151-2.77xTRIMT µV/°C
TC2=-0.528-0.00128x
TRIMT µV/°C2
VREF Error (Note 1) -40 +40 ppm/°C
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Electrical Characteristics (continued)
(Limits are production tested at TA=+25°C.Limitsovertheoperatingtemperaturerangeandreleventsupplyvoltagerangeareguaran-
teed by design and characterization.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
ADC
Recommended Input Range
(All Analog Inputs Relative
to VV3P3A)
-250 +250 mV Peak
Recommended Input Range,
IADC0–IADC1, Preamp
Enabled
-31.25 +31.25 mV Peak
Input Impedance fIN=65Hz 40 100 kΩ
ADC Gain Error vs. Power
Supply VIN=200mVpeak,65Hz,VV3P3A=3.0Vto3.6V -30 +70 ppm/%
Input Offset Voltage Differential or single-ended modes -10 +10 mV
THD
250mV peak, 65Hz, 64k points, Blackman-Harris
window,FIR_LEN=2,ADC_DIV=1,PLL_FAST=1,
MUX_DIV=2
-93
dB
20mV peak, 65Hz, 64k points, Blackman-Harris
window,FIR_LEN=2,ADC_DIV=1,PLL_FAST=1,
MUX_DIV=2
-90
LSB Size FIR_LEN=2,ADC_DIV=1,PLL_FAST=1,MUX_
DIV=2 151 nV
Digital Full Scale FIR_LEN=2,ADC_DIV=1,PLL_FAST=1,MUX_
DIV=2 ±2,097,152 LSB
PREAMPLIFIER
Differential Gain 7.88 7.98 8.08 V/V
Gain Variation vs. Temperature TA=-40°Cto+85°C(Note1) +15 -25 -30 ppm/°C
Gain Variation vs. V3P3 VV3P3=2.97Vto3.63V(Note1) -100 +100 ppm/%
Phase Shift (Note 1) +10 +22 m°
Preamp Input Current 3 6 9 µA
THD, Preamp + ADC VIN=30mV -88 dB
VIN=15mV -88
Preamp Input Offset Voltage
IADC0=IADC1=VV3P3 + 30mV -0.63
mV
IADC0=IADC1=VV3P3 + 15mV -0.57
IADC0=IADC1=VV3P3 -0.56
IADC0=IADC1=VV3P3 - 15mV -0.56
IADC0=IADC1=VV3P3 - 30mV -0.55
Phase Shift Over Temperature (Note 1) -0.03 +0.03 m°/C
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Energy Meter ICs
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Electrical Characteristics (continued)
(Limits are production tested at TA=+25°C.Limitsovertheoperatingtemperaturerangeandreleventsupplyvoltagerangeareguaran-
teed by design and characterization.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
FLASH MEMORY
Endurance 20,000 Cycles
Data Retention TA=+25°C 100 Years
Byte Writes Between Erase
Operations 2 Cycles
Write Time, per byte Per 2 bytes if using SPI 50 µs
Page Erase Time 22 ms
Mass Erase Time 22 ms
SPI
Data-to-Clock Setup Time 10 ns
Data Hold Time From Clock 10 ns
Output Delay, Clock to Data 40 ns
CS-to-Clock Setup Time 10 ns
Hold Time, CS to Clock 15 ns
Clock High Period 40 ns
Clock Low Period 40 ns
ClockFrequency(asamultiple
ofCPUfrequency) 2.0 MHz/MHz
Space between SPI
Transactions 4.5 CPU
Cycles
EEPROM INTERFACE
I2CSCLFrequency MPUclock=4.9MHz,usinginterrupts 310 kHz
MPUclock=4.9MHz,bit-bangingDIO2-DIO3 100
3-WireWriteClockFrequency MPUclock=4.9MHz,PLL_FAST=0 160 kHz
MPUclock=4.9MHz,PLL_FAST=1 490
RESET
Reset Pulse Width (Note 1) 5 µs
Reset Pulse Fall Time (Note 1) 1 µs
INTERNAL CALENDAR
Year Date Range 2000 2255 Years
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Recommended External Components
Note 1: Parameter not tested in production, guaranteed by design to six-sigma.
Note 2: IfthecapacitorvaluesofCXS=15pFandCXL=10pFhavealreadybeeninstalled,thenchangingtheCXLvalueto33pF
andleavingCXS=15pFwouldminimizerework.
NAME FROM TO FUNCTION VALUE UNITS
C1 VV3P3A GNDA Bypass capacitor for 3.3V supply ≥0.1±20% µF
C2 VV3P3D GNDD Bypass capacitor for 3.3V output 0.1 ±20% µF
CSYS VV3P3SYS GNDD Bypass capacitor for VV3P3SYS ≥1.0±30% µF
CVDD VDD GNDD Bypass capacitor for VDD 0.1 ±20% µF
CVLCD VLCD GNDD Bypass capacitor for VLCD pin ≥0.1±20% µF
XTAL XIN XOUT
32.768kHzcrystal;electricallysimilartoECS
.327-12.5-17X, Vishay XT26T or Suntsu SCP6–
32.768kHz TR (load capacitance 12.5pF)
32.768 kHz
CXS
(Note 2) XIN GNDA Load capacitor values for crystal depend on crystal
specicationsandboardparasitics.Nominal
values are based on 3pF allowance for the sum
of board and chip capacitance.
22 ±10% pF
CXL
(Note 2) XOUT GNDA 22 ±10% pF
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Pin Congurations
71M6541DT
71M6541FT
71M6541GT
LQFP
(10mm x 10mm)
TOP VIEW
12 45673
30
29
28
27
26
25
24
23
22
21
20
19
18
17
31
32
51
52
53
54
55
56
57
58
59
60
61
62
63
64
50
49
8910 11 12 13 14 15 16
48 47 45 44 43 4246 41 40 39 38 37 36 35 34 33
SPI_DI/SEGDIO38
SPI_CSZ/SEGDIO36
COM1
COM2
COM3
COM0
SEGDIO27/COM4
SPI_DO/SEGDIO37
SEGDIO26/COM5
SEGDIO25
SEGDIO24
SEGDIO23
SEGDIO22
SEGDIO21
SEGDIO20
SEGDIO19
SEGDIO1/VPULSE
SEGDIO3/SDATA
OPT_RX/SEGDIO55
SEGDIO14
SEGDIO13
SEGDIO10
SEGDIO9
SEGDIO5
SEGDIO4
SEGDIO11
SEGDIO12
SEGDIO8/DI
SEGDIO7/YPULSE
SEGDIO6/XPULSE
SEGDIO2/SDCK
SEGDIO0/WPULSE
TX
VV3P3D
VV3P3SYS
XIN
GNDD
VBAT
ICE_E
OPT_TX/SEGDIO51
VBAT_RTC
E_RXTX/SEG48
E_TCLK/SEG49
E_RST//SEG48
RX
VDD
IBP
IBN
TMUXOUT/SEG47
SEGDIO45
VV3P3A
GNDA
VA
PB
VLCD
TEST
XOUT
IAP
IAN
RESET
TMUX2OUT/SEG46
SEGDIO44
SPI_CKI/SEGDIO39
VREF
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Pin Congurations (continued)
1 75
2 74
3 73
4 72
5 71
7 69
8 68
9 67
25 51
TOP VIEW
6 70
11 65
12 64
13 63
15 61
16 60
17 59
10 66
14 62
18 58
19 57
20 56
22 54
23 53
24 52
21 55
LQFP
(14mm x 14mm)
26
100
27
99
28
98
29
97
30
96
31
95
32
94
33
93
34
92
35
91
36
90
37
89
38
88
39
87
40
86
41
85
42
84
43
83
44
82
45
81
46
80
47
79
48
78
49
77
50
76
+
71M6542FT
71M6542GT
SPI_DI/SEGDIO38
SPI_CSZ/SEGDIO36
COM1
COM2
COM3
COM0
SEGDIO27/COM4
SPI_DO/SEGDIO37
SEGDIO26/COM5
SEGDIO25
SEGDIO24
SEGDIO23
SEGDIO22
SEGDIO21
SEGDIO20
SEGDIO19
SEGDIO35
SEGDIO33
SEGDIO32
SEGDIO30
SEGDIO29
SEGDIO31
SEGDIO28
SEGDIO34
SEGDIO18
SEGDIO17
SEGDIO1/VPULSE
SEGDIO3/SDATA
N.C.
OPT_RX/SEGDIO55
SEGDIO16
SEGDIO15
SEGDIO14
SEGDIO13
SEGDIO10
SEGDIO11
SEGDIO12
SEGDIO9
SEGDIO8/DI
SEGDIO7/YPULSE
SEGDIO6/XPULSE
SEGDIO5
SEGDIO4
SEGDIO2/SDCK
SEGDIO0/WPULSE
SEGDIO54
N.C.
N.C.
N.C.
N.C.
TX
VV3P3D
VV3P3SYS
XIN
GNDD
VBAT
ICE_E
SEGDIO52
OPT_TX/SEGDIO51
IBN
IBP
GNDA
VBAT_RTC
E_RXTX/SEG48
E_TCLK/SEG49
E_RST/SEG50
RX
SEGDIO53
VDD
N.C.
N.C.
N.C.
N.C.
N.C.
N.C.
TMUXOUT/SEG47
SEGDIO45
VA
VV3P3A
GNDA
N.C.
PB
VLCD
TEST
XOUT
IAP
IAN
RESET
TMUX2OUT/SEG46
SEGDIO44
SEGDIO43
SEGDIO42
SEGDIO41
SEGDIO40
SPI_CKI/SEGDIO39
VREF
N.C.
N.C.
N.C.
VB
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Pin Descriptions
PIN NAME TYPE CIRCUIT FUNCTION
64 100
POWER AND GROUND PINS
50 72, 80 GNDA P — Analog Ground. This pin should be connected directly to the ground plane.
42 62 GNDD P — Digital Ground. This pin should be connected directly to the ground plane.
53 85 VV3P3A P — Analog Power Supply. A 3.3V power supply should be connected to this
pin. VV3P3A must be the same voltage as VV3P3SYS.
45 69 VV3P3SYS P — System 3.3V supply. This pin should be connected to a 3.3V power supply.
41 61 VV3P3D O 13
Auxiliary Voltage Output of the Chip. In mission mode, this pin is
connected to VV3P3SYS by the internal selection switch. In BRN mode,
it is internally connected to VBAT. VV3P3DisoatinginLCDandsleep
mode. A 0.1µF bypass capacitor to ground must be connected to this
pin.
40 60 VDD O —
Output of the 2.5V Regulator. This pin is powered in MSN and BRN
modes. A 0.1µF bypass capacitor to ground should be connected to this
pin.
57 89 VLCD O — Output of the LCD DAC. A 0.1µF bypass capacitor to ground should be
connected to this pin.
46 70 VBAT P 12
Battery Backup Pin to Support the Battery Modes (BRN, LCD). A battery
or super capacitor is to be connected between VBAT and GNDD. If no
battery is used, connect VBAT to VV3P3SYS.
47 71 VBAT_RTC P 12
RTC and Oscillator Power Supply. A battery or super capacitor is to be
connected between VBAT and GNDD. If no battery is used, connect
VBAT_RTC to VV3P3SYS.
ANALOG PINS
55,
54
87,
86 IAP-IAN
I 6
Differential or Single-Ended Line Current Sense Inputs. These pins
are voltage inputs to the internal A/D converter. Typically, they are
connected to the outputs of current sensors. Unused pins must be tied
to VV3P3A.PinsIBP-IBNmaybeconguredforcommunicationwiththe
remote sensor interface (71M6x01).
44,
43
68,
67 IBP-IBN
52 82, 83 VA, VB† I 6
Line Voltage Sense Inputs. These pins are voltage inputs to the internal
A/D converter. Typically, they are connected to the outputs of resistor-
dividers. Unused pins must be tied to VV3P3A.
56 88 VREF O 9 Voltage Reference for the ADC. This pin should be left unconnected
(oating).
48 75 XIN I
8
Crystal Inputs. A 32.768kHz crystal should be connected across these
pins. Typically, a 22pF capacitor is also connected from XIN to GNDA
and a 22pF capacitor is connected from XOUT to GNDA. It is important
to minimize the capacitance between these pins. See the crystal
manufacturer data sheet for details. If an external clock is used, a
150mVP-P clock signal should be applied to XIN, and XOUT should be
left unconnected.
49 76 XOUT O
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Pin Descriptions (continued)
PIN NAME TYPE CIRCUIT FUNCTION
64 100
DIGITAL PINS
4-7 12–15 COM0–COM3 O 5 LCD Common Outputs. These four pins provide the select signals for
the LCD display.
31 45 SEGDIO0/WPULSE
I/O 3, 4, 5
Multiple-UsePins.CongurableaseitherLCDsegmentdriverorDIO.
Alternative functions with proper selection of associated I/O RAM
registers are:
SEGDIO0=WPULSE
SEGDIO1=VPULSE
SEGDIO2=SDCK
SEGDIO3=SDATA
SEGDIO6=XPULSE
SEGDIO7=YPULSE
SEGDIO8=DI
SEGDIO16=RX3
SEGDIO17=TX3
UnusedpinsmustbeconguredasoutputsorterminatedtoV3P3/
GNDD.
30 44 SEGDIO1/VPULSE
29 43 SEGDIO2/SDCK
28 42 SEGDIO3/SDATA
27 41 SEGDIO4
26 39 SEGDIO5
25 38 SEGDIO6/XPULSE
24 37 SEGDIO7/YPULSE
23 36 SEGDIO8/DI
22-17 35–30 SEGDIO[9:14]
— 29–27 SEGDIO[15:17]
— 25 SEGDIO[18]
16-10 24–18 SEGDIO[19:25]
— 11–4 SEGDIO[28:35]
63-62 95–94 SEGDIO[44:45]
— 99–96 SEGDIO[40:43]
— 52 SEGDIO52
— 51 SEGDIO53
— 47 SEGDIO54
9 17 SEGDIO26/COM5 I/O 3, 4, 5 Multiple-UsePins.CongurableaseitherLCDsegmentdriverorDIO
with alternative function (LCD common drivers).
8 16 SEGDIO27/COM4
3 3 SPI_CSZ/SEGDIO36
I/O 3, 4, 5 Multiple-UsePins.CongurableaseitherLCDsegmentdriverorDIO
with alternative function (SPI interface).
2 2 SPI_DO/SEGDIO37
1 1 SPI_DI/SEGDIO38
64 100 SPI_CKI/SEGDIO39
33 53 OPT_TX/SEGDIO51 I/O 3, 4, 5 Multiple-UsePins,congurableaseitherLCDsegmentdriverorDIO
with alternative function (optical port/UART1)
32 46 OPT_RX/SEGDIO55
38 58 E_RXTX/SEG48 I/O 1, 4, 5 MultiusePins.Congurableaseitheremulatorportpins(whenICE_E
pulledhigh)orLCDsegmentdrivers(whenICE_EtiedtoGND).
36 56 E_RST/SEG50
37 57 E_TCLK/SEG49 O 4, 5
39 59 ICE_E I 2
ICEEnable.Whenzero,E_RST,E_TCLK,andE_RXTXbecome
SEG50, SEG49, and SEG48, respectively. For production units, this pin
should be pulled to GND to disable the emulator port.
60 92 TMUXOUT/SEG47 O 4, 5 Multiple-UsePins.Congurableaseithermultiplexer/clockoutputor
LCD segment driver using the I/O RAM registers.
61 93 TMUX2OUT/SEG46
59 91 RESET I 2
Chip Reset. This input pin is used to reset the chip into a known state.
For normal operation, this pin is pulled low. To reset the chip, this pin
should be pulled high. This pin has an internal 30FA (nominal) current
source pulldown. No external reset circuitry is necessary.
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Pin Descriptions (continued)
I = Input, O = Output, P = Power
PIN NAME TYPE CIRCUIT FUNCTION
64 100
35 55 RX I 3 UART0 Input. If this pin is unused it must be terminated to VV3P3D or
GNDD.
34 54 TX O 4 UART0 Output
51 81 TEST I 7 Enables Production Test. This pin must be grounded in normal
operation.
58 90 PB I 3
Pushbutton Input. This pin must be at GNDD when not active or
unused.ArisingedgesetstheWF_PBag.Italsocausesthepart
to wake up if it is in SLP or LCD mode. PB does not have an internal
pullup or pulldown resistor.
—
26, 40,
48, 49,
50, 63,
64, 65,
66, 73,
74, 77,
78, 79,
84
N.C. N.C. — No Connection. Do not connect these pins.
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Block Diagram
IAP
MUX
AND
PREAMP
XIN
XOUT
VREF
CKADC
CE
MPU
(80515)
OPT_RX/
SEGDIO55
OPT_TX/
SEGDIO51/
WPULSE/
VARPULSE
RESET
VBIAS
EMULATOR
PORT
3
CE_BUSY
OPTICAL
INTERFACE
UART0
TX
RX
XFER BUSY
6COM[0:5]
VLC2
LCD DRIVER
CEDATA
0x000...0x2FF
0x0000...0x13FF
PROG
0x000...0x3FF
DATA
0x0000...0xFFFF
PROGRAM
0x0000...0xFFFF
0x0000...
0xFFFF
DIGITAL I/O
0x2000...0x20FF
I/O RAM
MEMORY
SHARE
MEMORY
SHARE
16
8
RTCLK
RTCLK (32kHz)
MUX_SYNC
CKMPU
≤4.9MHz
CKCE
≤4.9MHz
CK32
32kHz
4.9MHz
4.9MHz
8
8
8
POWER FAULT
DETECTION
GNDD
V3P3D
VBAT
VOLTAGE
REGULATOR
2.5V TO LOGIC
VDD
MPU_RSTZ
FAULTZ
WAKE
CONFIGURATION
PARAMETERS
GNDAV3P3A
VBIAS
CROSS
CLOCK GEN
OSCILLATOR
32kHz
CK32
MCK
PLL
VREF
DIV
ADC
MUX CTRL
STRT
MUX
MUX
CKFIR
RTM
SEGDIO PINS
WPULSE
VARPULSE
WPULSE
VARPULSE
TEST TEST
MODE
VLC1
VLC0
CKMPU_2x
CKMPU_2x
SDCK
SDOUT
SDIN
E_RXTX/SEG48
E_TCLK/SEG49
E_RST/SEG50
FLASH
32/64/128KB
V3P3A
EEPROM
INTERFACE
CK_4X
LCD_GEN
PB
RTC
VBIAS
16
E_RXTX
E_TCLK
E_RST
ICE_E
∆∑
AD CONVERTER
VREF
V3P3SYS
TEST MUX
VLCD
VLCD
VOLTAGE
BOOST
MPU RAM
3/5KB
22
SPI
VSTAT
VBAT_RTC
IAN
IBP
IBN
VA
VB*
SEG PINS
2
TEST MUX
2
NON-VOLATILE
CONFIGURATION
RAM
CONFIGURATION
RAM
(I/O RAM)
BAT
TEST
TEMP
SENSOR
RTM
*71M6542FT/GT ONLY
FIR
32
CE CONTROL
32-BIT
COMPUTE
ENGINE
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Figure 1. I/O Equivalent Circuits
DIGITAL INPUT EQUIVALENT CIRCUIT
TYPE 1:
STANDARD DIGITAL INPUT OR
PIN CONFIGURED AS DIO INPUT
WITH INTERNAL PULL-UP
LCD OUTPUT EQUIVALENT CIRCUIT
TYPE 5:
LCD SEG OR
PIN CONFIGURED AS LCD SEG
V3P3D V3P3D
110kΩ
CMOS
INPUT
DIGITAL
INPUT
PIN
DIGITAL INPUT
TYPE 2:
PIN CONFIGURED AS DIO INPUT
WITH INTERNAL PULL-UP
V3P3D
110kΩ
CMOS
INPUT
DIGITAL
INPUT
PIN
LCD SEG
OUTPUT
PIN
LCD
DRIVER
GNDD
GNDD
GNDD ANALOG INPUT EQUIVALENT CIRCUIT
TYPE 6:
ADC INPUT
VREF EQUIVALENT CIRCUIT
TYPE 9:
VREF
V3P3D
VREF
PIN
FROM
INTERNAL
REFERENCE
GNDA
V2P5 EQUIVALENT CIRCUIT
TYPE 10:
V2P5
V3P3D
V2P5
PIN
FROM
INTERNAL
REFERENCE
GNDD
V3P3D
TO
MUX
ANALOG
INPUT
PIN
GNDA
DIGITAL INPUT
TYPE 3:
STANDARD DIGITAL INPUT OR
PIN CONFIGURED AS DIO INPUT
V3P3D
CMOS
INPUT
DIGITAL
INPUT
PIN
GNDD
DIGITAL OUTPUT EQUIVALENT CIRCUIT
TYPE 4:
STANDARD DIGITAL OUTPUT OR
PIN CONFIGURED AS DIO OUTPUT
V3P3D
V3P3D
CMOS
OUTPUT
DIGITAL
OUTPUT
PIN
GNDD
COMPARATOR INPUT EQUIVALENT CIRCUIT
TYPE 7:
COMPARATOR INPUT
VLCD EQUIVALENT CIRCUIT
TYPE 11:
VLCD POWER
V3P3D
TO
COMPARATOR
COMPARATOR
INPUT
PIN
GNDA
LCD
DRIVERS
VLCD
PIN
GNDD
OSCILLATOR EQUIVALENT CIRCUIT
TYPE 8:
OSCILLATOR I/O
V3P3D EQUIVALENT CIRCUIT
TYPE 13:
V3P3D
TO
OSCILLATOR
OSCILLATOR
PIN
GNDD
VBAT EQUIVALENT CIRCUIT
TYPE 12:
VBAT POWER
POWER
DOWN
CIRCUITS
VBAT
PIN
GNDD
10Ω
40Ω
V3P3D
PIN
FROM
V3P3SYS
FROM
VBAT
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Hardware Description
The 71M6541DT/FT/GT and 71M6542FT/GT single-chip
energy meter ICs integrate all primary functional blocks
requiredtoimplementasolid-stateresidentialelectricity
meter. Included on the chip are the following:
• An analog front-end (AFE) featuring a 22-bit second-
order sigma-delta ADC
• An independent 32-bit digital computation engine (CE)
to implement DSP functions
• An 8051-compatible microprocessor (MPU) which
executes one instruction per clock cycle (80515)
• A precision voltage reference (VREF)
• A temperature sensor for digital temperature compensation:
• Metrology digital temperature compensation (MPU)
• Automatic RTC digital temperature compensation
operational in all power states
• LCD drivers
• RAM and flash memory
• A real-time clock (RTC)
• A variety of I/O pins
• A power-failure interrupt
• A zero-crossing interrupt
• Selectable current sensor interfaces for locally-connect-
ed sensors as well as isolated sensors (i.e., using the
71M6x01 companion IC with a shunt resistor sensor)
• Resistive shunt and current transformers are supported
Resistive shunts and current transformer (CT) current
sensors are supported. Resistive shunt current sensors
may be connected directly to the 71M654xT device
or isolated using a companion 71M6x01 isolator IC
in order to implement a variety of single-phase/split-
phase (71M6541DT/FT/GT) or two-phase (71M6542FT/
GT) metering configurations. An inexpensive, small pulse
transformer is used to isolate the 71M6x01 isolated
sensor from the 71M654xT. The 71M654xT performs
digital communications bidirectionally with the 71M6x01
and also provides power to the 71M6x01 through the
isolating pulse transformer. Isolated (remote) shunt
current sensors are connected to the differential input
of the 71M6x01. Included on the 71M6x01 companion
isolator chip are:
• Digital isolation communications interface
• An analog front-end (AFE)
• A precision voltage reference (VREF)
• A temperature sensor (for digital temperature compen-
sation)
• A fully differential shunt resistor sensor input
• A preamplifier to optimize shunt current sensor perfor-
mance
• Isolated power circuitry obtains dc power from pulses
sent by the 71M654xT
In a typical application, the 32-bit compute engine (CE)
of the 71M654xT sequentially processes the samples
from the voltage inputs on analog input pins and from
the external 71M6x01 isolated sensors and performs
calculations to measure active energy (Wh) and reactive
energy (VARh), as well as A2h, and V2hforfour-quadrant
metering. These measurements are then accessed by the
MPU, processed further and output using the peripheral
devices available to the MPU.
In addition to advanced measurement functions, the clock
function allows the 71M6541DT/FT/GT and 71M6542FT/
GT to record time-of-use (TOU) metering information
for multi-rate applications and to time-stamp tamper or
other events. Measurements can be displayed on 3.3V
LCDs commonly used in low-temperature environments.
Flexible mapping of LCD display segments facilitate
integration of existing custom LCDs. Design trade-off
between the number of LCD segments and DIO pins can
be implemented in software to accommodate various
requirements.
In addition to the temperature-trimmed ultra-precision
voltage reference, the on-chip digital temperature
compensation mechanism includes a temperature sensor
and associated controls for correction of unwanted
temperature effects on measurement and RTC accuracy,
e.g.,tomeettherequirementsofANSIandIECstandards.
Temperature-dependent external components such as
crystal oscillator, resistive shunts, current transformers
(CTs) and their corresponding signal conditioning circuits
can be characterized and their correction factors can be
programmed to produce electricity meters with exceptional
accuracy over the industrial temperature range.
One of the two internal UARTs is adapted to support an
Infrared LED with internal drive and sense configuration
and can also function as a standard UART. The optical
output can be modulated at 38kHz. This flexibility makes
it possible to implement AMR meters with an IR interface.
See the Block Diagram.
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Figure 2. 71M6541DT/FT/GT Operating with Local Sensors
Figure 3. 71M6541DT/FT/GT Operating with Remote Sensor for Neutral Current
Analog Front-End (AFE)
TheAFEfunctionsasadataacquisitionsystem,controlled
by the MPU. When used with locally connected sensors,
as shown in Figure 2, the analog input signals (IAP-IAN,
VA and IBP-IBN) are multiplexed to the ADC input and
sampled by the ADC.
The ADC output is decimated by the FIR filter and stored
in CE RAM where it can be accessed and processed by
the CE.
When a remote isolated shunt sensor is connected via
the 71M6x01, the samples associated with this current
channel are not routed to the multiplexer, and are instead
transferred digitally to the 71M6541DT/FT/GT through the
digital isolation interface and are directly stored in CE RAM.
When local sensors are used, the analog input signals
(IAP-IAN, VA, IBP-IBN and VB) are multiplexed to the
ADC input and sampled by the ADC. The ADC output is
decimated by the FIR filter and stored in CE RAM where
it can be accessed and processed by the CE.
When a remote isolated shunt sensor is connected using
a 71M6x01 connected to the 71M6542FT/GT, the samples
associated with this current channel are not routed to the
multiplexer, and are instead transferred digitally to the
71M6542FT/GT through the digital isolation interface and
are directly stored in CE RAM.
∆∑ ADC
CONVERTER
VREF
MUX
VREF
VREF
VADC 22
FIR
IBP
IAP
VADC10 (VA)
IAN
IBN
71M6541DT/FT/GT
CE RAM
*IN = OPTIONAL NEUTRAL CURRENT
LOCAL
SHUNT
IN*
OR
CT
I
LINE
CT
I
LINE
∆∑ ADC
CONVERTER
VREF
MUX
VREF
VREF
VADC 22
22
FIR
IAP
VADC10 (VA)
IAN
CE RAM
LOCAL
SHUNT
ILINE
REMOTE
SHUNT
IN*
71M6541DT/FT/GT
71M6x01
* IN = OPTIONAL NEUTRAL CURRENT
IBP
IBN
SP
SN
INP
INN
DIGITAL
ISOLATION
INTERFACE
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Figure 4. 71M6542FT/GT Operating with Local Sensors
Figure 5. 71M6542FT/GT Operating with Remote Sensor for Neutral Current
∆∑ ADC
CONVERTER
VREF
MUX
VREF
VREF
VADC 22
FIR
IBP
IAP
VADC10 (VA)
IAN
IBN
71M6542FT/GT
CE RAM
LOCAL
SHUNT
IB
OR
CT
IA
CT
VADC9 (VB)
IA
∆∑ ADC
CONVERTER
VREF
MUX
VREF
VREF
VADC 22
22
FIR
IAP
VADC10 (VA)
IAN
CE RAM
LOCAL
SHUNT
IA
VADC9 (VB)
REMOTE
SHUNT
IB
71M6542FT/GT
71M6x01
* IN = OPTIONAL NEUTRAL CURRENT
IBP
IBN
SP
SN
INP
INN
DIGITAL
ISOLATION
INTERFACE
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Signal Input Pins
The 71M6541DT/FT/GT features five ADC inputs. The
71M6542FT/GT features six ADC inputs.
IAP-IAN and IBP-IBN are intended for use as current sen-
sor inputs. These four current sensor inputs can be con-
figuredastwosingle-endedinputs,or(morefrequently)
can be paired to form two differential inputs. For best
performance, it is recommended to configure the current
sensor inputs as differential inputs (i.e., IAP-IAN and IBP-
IBN). The first differential input (IAP-IAN) features a pre-
amplifier with a selectable gain of 1 or 8, and is intended
for direct connection to a shunt resistor sensor, and can
also be used with a current transformer (CT). The remain-
ing differential pair (i.e., IBP-IBN) may be used with CTs,
or may be enabled to interface to a remote 71M6x01 iso-
lated current sensor providing isolation for a shunt resistor
sensor using a low cost pulse transformer.
The remaining input in the 71M6541DT/FT/GT (VA) is
single-ended, and is senses line voltage in single-phase
meter applications. The 71M6542FT/GT features an
additional single-ended voltage sensing input (VB) to
support biphase applications. These single-ended inputs
are referenced to the VV3P3A pin.
All analog signal input pins measure voltage. In the
case of shunt current sensors, currents are sensed as
a voltage drop in the shunt resistor sensor. Referring
to Figure 2, shunt sensors can be connected directly to
the 71M654xT (referred to as a ‘local’ shunt sensor) or
connected through an isolated 71M6x01 (referred to as a
‘remote’ shunt sensor) (Figure 3). In the case of current
transformers, the current is measured as a voltage across
a burden resistor that is connected to the secondary
winding of the CT. Meanwhile, line voltages are sensed
through resistive voltage dividers. The VA and VB pins
(VB is available in the 71M6542FT/GT only) are single-
ended and their common return is the VV3P3A pin.
Pins IAP-IAN can be programmed individually to be differ-
ential or single-ended. For most applications IAP-IAN are
configured as a differential input to work with a shunt or
CT directly interfaced to the IAP-IAN differential input with
the appropriate external signal conditioning components.
The performance of the IAP-IAN pins can be enhanced by
enabling a preamplifier with a fixed gain of 8. When the
PRE_Ebit=1,IAP-IANbecometheinputstothe8xpre-
amplifier, and the output of this amplifier is supplied to the
multiplexer. The 8x amplification is useful when current
sensors with low sensitivity, such as shunt resistors, are
used.WithPRE_Eset,theIAP-IANinputsignalamplitude
is restricted to 31.25 mV peak.
For the 71M654xT application utilizing two shunt resistor
sensors the IAP-IAN pins are configured for differential
modetointerfacetoalocalshuntbysettingtheDIFFA_E
control bit. Meanwhile, the IBP-IBN pins are re-configured
as digital balanced pair to communicate with a 71M6x01
isolatedsensorinterfacebysettingtheRMT_Econtrolbit.
The 71M6x01 communicates with the 71M654xT using
a bidirectional digital data stream through an isolating
low-cost pulse transformer. The 71M654xT also supplies
power to the 71M6x01 through the isolating transformer.
When using current transformers the IBP-IBN pins are
configured as local analog inputs (RMT_E = 0). The
IAP-IAN pins cannot be configured as a remote sensor
interface.
Input Multiplexer
When operating with local sensors, the input multiplexer
sequentially applies the input signals from the analog
input pins to the input of the ADC. One complete sampling
sequenceis called a multiplexerframe.Themultiplexer
of the 71M6541DT/FT/GT can select up to three input
signals (IAP-IAN, VA, and IBP-IBN) per multiplexer frame.
The multiplexer of the 71M6542FT/GT adds the VB signal
for a total of four inputs. The multiplexer always starts at
state 1 and proceeds until as many states as determined
byMUX_DIV[3:0]havebeenconverted.
The 71M6541DT/FT/GT and 71M6542FT/GT each require
auniqueCEcodethatiswrittenforthespecificapplication.
Moreover,eachCEcoderequiresspecificAFEandMUXset-
tings in order to function properly. Contact Maxim Integrated
for specific information about alternative CE codes.
For a basic single-phase application, the IAP-IAN current
input is configured for differential mode and the VA pin is
single-ended and is typically connected to the phase volt-
age via a resistor divider. The IBP-IBN differential input
may be optionally used to sense the neutral current. This
configuration implies that the multiplexer applies a total of
three inputs to the ADC. In this configuration IAP-IAN (line
current), IBP-IBN (neutral current) and VA (line voltage)
aresampled.Iftheapplicationdoesn’trequiresampling
the neutral current, the IBP-IBN inputs can be connected
to VV3P3A and the current sensor for the neutral current
measurement can be omitted.
Ifatampersensorintheneutralpathisrequired,there
are two options: first, the two current inputs (the pin pairs
IAP-IAN and IBP-IBN) can be con figured for differential
mode. In this configuration, the multiplexer sequentially
applies each of the three inputs to the ADC. Alternately,
the IAP-IAN pin pair can be configured as a differential
input and connected to a local current shunt, and IBP-IBN
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Figure 6. Multiplexer Sequence with MUX_DIV = 3
Figure 7. Multiplexer Sequence with MUX_DIV = 4
configured to connect to an isolated 71M6x01 isolated
sensor. When the remote isolated sensor is used, time
slot 2 is unused and ignored by the CE, as the samples
corresponding to the remote sensor (IBP-IBN) do not
pass through the multiplexer and are stored directly in CE
RAM. The remote current sensor channel is sampled dur-
ing the second half of the multiplexer frame and its timing
relationship to the VA voltage is precisely known so that
delay compensation can be properly applied.
The 71M6542FT/GT adds the ability to sample a second
phase voltage (applied at the VB pin), which makes it
suitable for meters with two voltage and two current
sensors, such as meters implementing Equation 2 for
dual-phaseoperation(P=VAxIA+VBxIB).
Forbothmultiplexersequences(three-inputorfour-input),
the frame duration is 13 CK32 cycles (where CK32 =
32,768Hz) making the resulting sample rate 32,768Hz/13
=2520.6Hz.
Delay Compensation
When measuring the energy of a phase (i.e., Wh and
VARh) in a service, the voltage and current for that phase
must be sampled at the same instant. Otherwise, the
phasedifference,Ф,introduceserrors.
delay
delay
t
360 t f 360
T
ϕ= ⋅°= ⋅⋅°
Wherefisthefrequencyoftheinputsignal,T=1/fand
tdelay is the sampling delay between current and voltage.
Tradition ally, sampling is accomplished by using two A/D
converters per phase (one for voltage and the other one
for current) controlled to sample simultaneously. Our
Single Converter Technology, however, ex ploits the 32-bit
signal processing capability of its CE to implement “con-
stant delay” allpass filters. The allpass filter corrects for
the conversion time difference between the voltage and
CK32
MUX STATE 0
IA
IA
IA
1
VA
VA
VA
2
IB
NOT USED
VB
MUX_DIV[3:0] = 3 CONVERSIONS
MULTIPLEXER FRAME
S
CROSS
MUX_SYNC
0S
SETTLE
CK32
MUX_DIV = 4 CONVERSIONS
MULTIPLEXER FRAME
CROSS
MUX_SYNC
MUX STATE0
IA
1
VA
2
IB
3
VB
S0S
SETTLE
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the corresponding current samples that are obtained with
a single multiplexed A/D converter.
The “constant delay” allpass filter provides a broad-band
delay360°–θ,whichispreciselymatchedtothediffer-
ence in sample time between the voltage and the current
of a given phase. This digital filter does not affect the
amplitude of the signal, but provides a precisely controlled
phase response.
The recommendedADC multiplexer sequence samples
the current first, immediately followed by sampling of the
corresponding phase voltage, thus the voltage is delayed
by a phase angle Ф relative to the current. The delay
compensation implemented in the CE aligns the voltage
samples with their corresponding current samples by first
delaying the current samples by one full sample interval
(i.e., 360°), then routing the voltage samples through
the allpass filter, thus delaying the voltage samples by
360o - θ, resulting in the residual phase error between
thecurrentanditscorrespondingvoltageofB–Ф.The
residual phase error is negligible, and is typically less than
±1.5 milli-degrees at 100Hz, thus it does not contribute to
errors in the energy measurements.
When using remote sensors, the CE performs the same
delay compensation described above to align each volt-
age sample with its corresponding current sample. Even
though the remote current samples do not pass through
the 71M654xT multiplexer, their timing relationship to their
corresponding voltages is fixed and precisely known.
ADC Preamplier
The ADC preamplifier is a low-noise differential amplifier
with a fixed gain of 8 available only on the IAP-IAN sensor
inputpins.Againof8isenabledbysettingPRE_E=1.
When disabled, the supply current of the preamplifier
is < 10 nA and the gain is unity. With proper settings of
thePRE_EandDIFFA_E(I/ORAM0x210C[4])bits,the
preamplifier can be used whether or not differential mode
is selected. For best performance, the differential mode
is recommended. In order to save power, the bias current
of the preamplifier and ADC is adjusted according to the
ADC_DIVcontrolbit(I/ORAM0x2200[5]).
Analog-to-Digital Converter (ADC)
A single 2nd-order delta-sigma ADC digitizes the voltage
and current inputs to the device. The resolution of the
ADC,includingthesignbit,is21bits(FIR_LEN[1:0]=1),
or22bits(FIR_LEN[1:0]=2).
InitiationofeachADCconversioniscontrolledbyMUX_
CTRL internal circuit. At the end of each ADC conversion,
the FIR filter output data is stored into the CE RAM loca-
tion determined by the multiplexer selection. FIR data is
stored LSB justified, but shifted left 9 bits.
FIR Filter
The finite impulse response filter is an integral part of the
ADC and it is optimized for use with the multiplexer. The
purpose of the FIR filter is to decimate the ADC output to
the desired resolution. At the end of each ADC conver-
sion, the output data is stored into the fixed CE RAM
location determined by the multiplexer selection.
Voltage References
A bandgap circuit provides the reference voltage to the
ADC. The VREF band-gap amplifier is chopper-stabilized
to remove the dc offset voltage. This offset voltage is the
most significant long-term drift mechanism in voltage ref-
erence circuits.
Isolated Sensor Interface
Nonisolating sensors, such as shunt resistors, can be con-
nected to the inputs of the 71M654xT through a combina-
tion of a pulse transformer and a 71M6x01 isolated sen-
sor interface. The 71M6x01 receives power directly from
Table 1. ADC Input Configuration
PIN ADC
CHANNEL
REQUIRED
SETTING COMMENT
IAP ADC0 DIFFA_E = 1 Differential mode must be selected with DIFFA_E=1.TheADCresultsarestoredinADC0
and ADC1 is not disturbed.
IAN ADC1
IBP ADC2 DIFFB_E = 1
or
RMT_E = 1
For locally connected sensors the differential input must be enabled by setting DIFFB_E.
For the remote connected sensor with a remote shunt, RMT_E must be set.
In both cases, the ADC results are stored in RAM location ADC2 and ADC3 is not disturbed.
IBN ADC3
VA ADC10 — Single-ended mode only. The ADC result is stored in ADC10.
VB ADC9 — Single-ended mode only (71M6542FT/GT only). The ADC result is stored in RAM location
ADC9.
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the 71M654xT through a pulse transformer and does not
require a dedicated power supply circuit. The 71M6x01
establishes 2-way communication with the 71M654xT,
supplying current samples and auxiliary information such
as sensor temperature via a serial data stream.
One 71M6x01 isolated sensor can be supported by the
71M6541DT/FT/GT and 71M6542FT/GT. When remote
interface IBP-IBN is en abled, the two analog current
inputs pins IBP and IBN become a digital balanced dif-
ferential interface to the remote sensor. Each 71M6x01
isolated sensor consists of the following building blocks:
• Power supply for power pulses received from the
71M654xT
• Digital communications interface
• Shunt signal preamplifier
• Delta-sigma ADC converter with precision bandgap
reference (chopping amplifier)
• Temperature sensor
• Fuse system containing part-specific information
During an ordinary multiplexer cycle, the 71M654xT inter-
nally determines which other channels are enabled. At
the same time, it decimates the modulator output from the
71M6x01 isolated sensors. Each result is written to CE
RAM during one of its CE access time slots.
The ADC of the 71M6x01 derives its timing from the
power pulses generated by the 71M654xT and as a
result, operates itsADC slaved to the frequency of the
power pulses. The generation of power pulses, as well as
the communication protocol between the 71M654xT and
71M6x01 isolated sensor is au tomatic and transparent to
the user.
The 71M654xT can read data and status from, and can
write control information to the 71M6x01 isolated sen-
sor. With hardware and trim-related information on each
connected 71M6x01 isolated sensor available to the
71M6541DT/FT/GT, the MPU can implement temperature
compensation of the energy measurement based on the
individual temperature characteristics of the 71M6x01
isolated sensor.
Digital Computation Engine (CE)
The CE, a dedicated 32-bit signal processor, performs the
precision computations necessary to accurately measure
energy. The CE calculations and processes include:
• Multiplication of each current sample with its associ-
ated voltage sample to obtain the energy per sample
(when multiplied with the constant sample time).
• Frequency-insensitive delay cancellation on all four
channels (to compensate for the delay bet ween sam-
ples caused by the multiplexing scheme).
• 90° phase shifter (for VAR calculations).
• Pulse generation.
• Monitoringoftheinputsignalfrequency(forfrequency
and phase information).
• Monitoring of the input signal amplitude (for sag detec-
tion).
• Scaling of the processed samples based on calibration
coefficients.
• Scaling of samples based on temperature compensa-
tion information.
Meter Equations
The 71M6541DT/FT/GT and 71M6542FT/GT provide
hardware assistance to the CE in order to support vari-
ousmeterequations.Thecomputeenginefirmwarefor
industrial configurations can implement the equations
listed in Table 2.EQU[2:0]specifiestheequationtobe
used based on the meter configuration and on the num-
ber of phases used for metering.
Real-Time Monitor
The CE contains a real-time monitor (RTM), which can be
programmed to monitor four selectable XRAM locations at
full sample rate. The four monitored locations are serially
output to the TMUXOUT pin via the digital output multi-
plexer at the beginning of each CE code pass. The RTM
canbeenabledanddisabledwithcontrolbitRTM_E.The
RTM output is clocked by CKTEST. Each RTM word is
clockedoutin35CKCEcycles(1CKCEcycleisequiva-
lent to 203ns) and contains a leading flag bit.
Pulse Generators
The 71M6541DT/FT/GT and 71M6542FT/GT provide
four pulse generators, VPULSE, WPULSE, XPULSE and
YPULSE, as well as hardware support for the VPULSE
and WPULSE pulse generators. The pulse generators
can be used to output CE status indicators (for example,
voltage sag) to DIO pins. All pulses can be configured to
generate interrupts to the MPU.
The polarity of the pulses may be inverted with control bit
PLS_INV.Whenthisbitisset,thepulsesareactivehigh,
ratherthanthemoreusualactivelow.PLS_INVinvertsall
four pulse outputs.
The function of each pulse generator is determined by
the CE code and the MPU code must configure the cor-
responding pulse outputs in agreement with the CE code.
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Table 2. Inputs Selected in Multiplexer Cycles
Note: Optionally, IB can be used to measure neutral current.
†71M6542FT/GT only.
Table 3. CKMPU Clock Frequencies
For example, standard CE code produces a mains zero-
crossing pulse on XPULSE and a SAG pulse on YPULSE.
A common use of the zero-crossing pulses is to gener-
ate interrupt in order to drive real-time clock software in
placeswherethemainsfrequencyissufficientlyaccurate
to do so and also to adjust for crystal aging. A common
use for the SAG pulse is to generate an interrupt that
alerts the MPU when mains power is about to fail, so that
the MPU code can store accumulated energy and other
data to EEPROM before the VV3P3SYS supply voltage
actually drops.
XPULSE and YPULSE
Pulses generated by the CE may be exported to the
XPULSE and YPULSE pulse output pins. Pins SEGDIO6
and SEGDIO7 are used for these pulses, respectively.
Generally, the XPULSE and YPULSE outputs can be
updated once on each pass of the CE code.
VPULSE and WPULSE
By default, WPULSE emits a pulse proportional to real
energy consumed, and VPULSE emits a pulse propor-
tional to reactive energy. During each CE code pass the
hardware stores exported WPULSE and VPULSE sign
bits in an 8-bit FIFO and sends the buffered sign bits to
the output pin at a specified, known interval. This permits
the CE code to calculate the VPULSE and WPULSE
outputs at the beginning of its code pass and to rely on
hardware to spread them over the multiplexer frame.
80515 MPU Core
The 71M6541DT/FT/GT and 71M6542FT/GT include an
80515 MPU (8-bit, 8051-compatible) that processes most
instructions in one clock cycle: a 4.9MHz clock results in
a processing throughput of 4.9 MIPS. The 80515 architec-
ture eliminates redundant bus states and im plements par-
allel execution of fetch and execution phases. Normally, a
machine cycle is aligned with a memory fetch, there fore,
most of the 1-byte instructions are performed in a single
machine cycle (MPU clock cycle). This leads to an 8x
average performance im prove ment (in terms of MIPS)
overthe8051devicerunningatthesameclockfrequency.
The CKMPU frequency is a function of the MCK clock
(19.6608MHz) divided by the MPU clock divider which
issetintheI/ORAMcontrolfieldMPU_DIV[2:0].Actual
processor clocking speed can be adjusted to the total pro-
cessing demand of the application (metering calculations,
AMR management, memory management, LCD driver
managementandI/Omanagement)usingMPU_DIV[2:0],
as shown in Table 3.
Memory Organization and Addressing
The 80515 MPU core incorporates the Harvard archi-
tecture with separate code and data spaces. Memory
organization in the 80515 is similar to that of the industry
standard 8051. There are three memory areas: program
memory (flash, shared by MPU and CE), external RAM
(data RAM, shared by the CE and MPU, configuration or
I/O RAM), and internal data memory (internal RAM).
Program Memory
The 80515 can address up to 64KB of program memory
space (0x0000 to 0xFFFF). Program memory is read
when the MPU fetches instructions or performs a MOVC
operation.
After reset, the MPU starts program execution from pro-
gram memory location 0x0000. The lower part of the pro-
EQU Description Wh and VARh formula Recommended Multiplexer
Se quence
Element 0 Element 1 Element 2
01-element,2-W,1φwithneutral
current sense VA ∙ IA VA ∙ IB1N/A IA VA IB1
11-element,3-W,1φ VA(IA-IB)/2 N/A N/A IA VA IB
2 † 2-element,3-W,1φ VA ∙ IA VB ∙ IB N/A IA VA IB VB
MPU_DIV [2:0] CKMPU FREQUENCY
000 4.9152MHz
001 2.4576MHz
010 1.2288MHz
011 614.4kHz
100
307.2kHz
101
110
111
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Table 4. Memory Map
*Memory size depends on IC. See the On-Chip Resources section for details.
gram memory includes reset and interrupt vectors. The
interrupt vectors are spaced at 8-byte in tervals, starting
from code space location 0x0003.
MPU External Data Memory (XRAM)
Both internal and external memory is physically located
on the 71M654xT device. The ex ternal mem ory referred
in this documentation is only external to the 80515 MPU
core.
3KB of RAM starting at address 0x0000 is shared by the
CE and MPU. The CE normally uses the first 1KB, leav-
ing 2KB for the MPU. Different versions of the CE code
use varying amounts. Consult the documentation for the
specific code version being used for the exact limit.
MOVX Addressing
There are two types of instructions differing in whether
they provide an 8-bit or 16-bit indirect address to the
external data RAM:
• MOVX A,@Ri: The contents of R0 or R1 in the current
register bank provide the eight low-order address bits
with the eight high-order bits specified by the PDATA
SFR. This method allows the user paged access (256
pages of 256 bytes each) to all ranges of the external
data RAM.
• MOVX A,@DPTR: The data pointer generates a 16-bit
address. This form is faster and more efficient when
accessing very large data arrays (up to 64KB) since no
additional instructions are needed to set up the eight
high ordered bits of the address.
It is possible to mix the two MOVX types. This provides
the user with four separate data pointers, two with direct
access and two with paged access, to the entire external
memory range.
Dual Data Pointer
The Dual Data Pointer accelerates the block moves of
data. The standard DPTR is a 16-bit register that is used
to address external memory or peripherals. In the 80515
core, the standard data pointer is called DPTR, the sec-
ond data pointer is called DPTR1. The data pointer select
bit, located in the LSB of the DPS register, chooses the
active pointer. DPTR is selected when DPS[0] = 0 and
DPTR1isselectedwhenDPS[0]=1.
The user switches between pointers by toggling the LSB
of the DPS register. The values in the data pointers are
not affected by the LSB of the DPS register. All DPTR
related instructions use the currently selected DPTR for
any activity.
An alternative data pointer is available in the form of the
PDATA register (SFR 0xBF), sometimes referred to as
USR2). It defines the high byte of a 16-bit address when
reading or writing XDATA with the instruction MOVX A,@
Ri or MOVX @Ri,A.
ADDRESS
(hex)
MEMORY
TECHNOLOGY
MEMORY
TYPE NAME TYPICAL USAGE MEMORY SIZE
(BYTES)
0000-7FFF
(32K)
0000-FFFF
(64K)
0000-1FFFFF
(128K)
Flash Memory Nonvolatile Program memory for MPU and
CE
MPU program and
nonvolatile data 128/64/32K*
CE program (on 1KB
boundary) 3K max
0000-0BFF Static RAM Volatile External RAM (XRAM) Shared by CE and MPU 5/3K*
2000-27FF Static RAM Volatile CongurationRAM(I/ORAM) Hardware control 2K
2800-287F Static RAM Nonvolatile
(battery) CongurationRAM(I/ORAM) Battery-buffered memory 128
0000-00FF Static RAM Volatile Internal RAM Part of 80515 Core 256
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Table 5. Internal Data Memory Map
Internal Data Memory Map and Access
The Internal data memory provides 256 bytes (0x00 to
0xFF) of data memory. The internal data memory address
is always 1 byte wide.
The Special Function Registers (SFR) occupy the upper
128 bytes. The SFR area of internal data memory is
available only by direct addressing. Indirect address-
ing of this area accesses the upper 128 bytes of Internal
RAM. The lower 128 bytes contain working registers and
bit addressable memory. The lower 32 bytes form four
banks of eight registers (R0-R7). Two bits on the program
memory status word (PSW, SFR 0xD0) select which bank
is in use. The next 16 bytes form a block of bit address-
able memory space at addresses 0x00-0x7F. All of the
bytes in the lower 128 bytes are accessible through direct
or indirect addressing.
Special Function Registers
Only a few addresses in the SFR memory space are
occupied; other addresses are unimplemented. A read
access to unimplemented addresses returns undefined
data, while a write access has no effect. SFRs specific to
the 71M654xT are shown in bold print on a shaded field.
The registers at 0x80, 0x88, 0x90, etc., are bit address-
able, all others are byte addressable.
Timers and Counters
The 71M6541DT/FT/GT and 71M6542FT/GT contain
two 16-bit timer/counter registers: Timer 0 and Timer 1.
These registers can be configured for counter or timer
operations.
In timer mode, the register is incremented every machine
cycle, i.e., it counts up once for every 12 periods of the
MPU clock. In counter mode, the register is incremented
Table 6. Special Function Register Map
ADDRESS RANGE DIRECT ADDRESSING INDIRECT ADDRESSING
0x80 0xFF Special Function Registers (SFRs) RAM
0x30 0x7F Byte addressable area
0x20 0x2F Bit addressable area
0x00 0x1F Register banks R0…R7
Hex/
Bin
Bit
Addressable Byte Addressable Bin/
Hex
X000 X001 X010 X011 X100 X101 X110 X111
F8 INTBITS VSTAT RCMD SPI_CMD FF
F0 B F7
E8 IFLAGS EF
E0 A E7
D8 WDCON DF
D0 PSW D7
C8 T2CON CF
C0 IRCON C7
B8 IEN1 IP1 S0RELH S1RELH PDATA BF
B0 P3 (DIO12:15) FLSH_CTL FLSH_
BANK
FLSH_
PGADR B7
A8 IEN0 IP0 S0RELL AF
A0 P2 (DIO8:11) A7
98 S0CON S0BUF IEN2 S1CON S1BUF S1RELL EEDATA EECTRL 9F
90 P1(DIO4:7) DPS FLSH_
ERASE 97
88 TCON TMOD TL0 TL1 TH0 TH1 CKCON 8F
80 P0 (DIO0:3) SP DPL DPH DPL1 DPH1 PCON 87
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Table 7. Generic 80515 SFRs: Location and Reset Values
NAME ADDRESS RESET VALUE DESCRIPTION
P0 0x80 0xFF Port 0
SP 0x81 0x07 Stack Pointer
DPL 0x82 0x00 Data Pointer Low 0
DPH 0x83 0x00 Data Pointer High 0
DPL1 0x84 0x00 Data Pointer Low 1
DPH1 0x85 0x00 Data Pointer High 1
PCON 0x87 0x00 UART Speed Control
TCON 0x88 0x00 Timer/Counter Control
TMOD 0x89 0x00 Timer Mode Control
TL0 0x8A 0x00 Timer 0, low byte
TL1 0x8B 0x00 Timer 1, high byte
TH0 0x8C 0x00 Timer 0, low byte
TH1 0x8D 0x00 Timer 1, high byte
CKCON 0x8E 0x01 ClockControl(Stretch=1)
P1 0x90 0xFF Port 1
DPS 0x92 0x00 Data Pointer select Register
S0CON 0x98 0x00 Serial Port 0, Control Register
S0BUF 0x99 0x00 Serial Port 0, Data Buffer
IEN2 0x9A 0x00 Interrupt Enable Register 2
S1CON 0x9B 0x00 Serial Port 1, Control Register
S1BUF 0x9C 0x00 Serial Port 1, Data Buffer
S1RELL 0x9D 0x00 Serial Port 1, Reload Register, low byte
P2 0xA0 0xFF Port 2
IEN0 0xA8 0x00 Interrupt Enable Register 0
IP0 0xA9 0x00 Interrupt Priority Register 0
S0RELL 0xAA 0xD9 Serial Port 0, Reload Register, low byte
P3 0xB0 0xFF Port 3
IEN1 0xB8 0x00 Interrupt Enable Register 1
IP1 0xB9 0x00 Interrupt Priority Register 1
S0RELH 0xBA 0x03 Serial Port 0, Reload Register, high byte
S1RELH 0xBB 0x03 Serial Port 1, Reload Register, high byte
PDATA 0xBF 0x00 High address byte for MOVX@Ri - also called USR2
IRCON 0xC0 0x00 InterruptRequestControlRegister
T2CON 0xC8 0x00 Polarity for INT2 and INT3
PSW 0xD0 0x00 Program Status Word
WDCON 0xD8 0x00 Baud Rate Control Register (only WDCON[7] bit used)
A0xE0 0x00 Accumulator
B0xF0 0x00 B Register
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when the falling edge is observed at the corresponding
input signal T0 or T1 (T0 and T1 are the timer gating
inputs derived from certain DIO pins, see 2.5.8 Digital
I/O). Since it takes 2 machine cycles to recognize a
1-to-0 event, the maximum input count rate is 1/2 of the
clockfrequency(CKMPU).Therearenorestrictionson
the duty cycle, how ever to ensure proper recognition of
the 0 or 1 state, an input should be stable for at least 1
machine cycle.
Four operating modes can be selected for Timer 0 and
Timer 1. The TMOD register is used to select the appro-
priate mode. The timer/counter operation is controlled by
the TCON register. Bits TR1 and TR0 in the TCON regis-
ter start their associated timers when set.
Interrupts
The 80515 provides 11 interrupt sources with four priority
levels.Eachsourcehasitsowninterruptrequestflag(s)
located in a special function register (TCON, IRCON, and
SCON). Each interrupt requested by the corresponding
interrupt flag can be individually enabled or disabled by
the interrupt enable bits in the IEN0, IEN1, and IEN2.
Referring to Figure 14, interrupt sources can origi-
nate from within the 80515 MPU core (referred to as
Internal Sources) or can originate from other parts of the
71M654xT SoC (referred to as External Sources). There
are seven external interrupt sources, (EX0-EX6).
Interrupt Overview
When an interrupt occurs, the MPU vectors to the prede-
termined address. Once the interrupt service has begun,
it can be interrupted only by a higher priority interrupt. The
interrupt service is terminated by a return from interrupt
instruction (RETI). When a RETI instruction is executed,
the processor returns to the instruction that would have
been next when the interrupt occurred.
When the interrupt condition occurs, the processor also
indicates this by setting a flag bit. This bit is set regardless
of whether the interrupt is enabled or disabled. Each inter-
rupt flag is sampled once per machine cycle, and then
samples are polled by the hardware. If the sample indi-
cates a pending interrupt when the interrupt is enabled,
thentheinterruptrequestflagisset.Onthenextinstruc-
tion cycle, the interrupt is acknowledged by hardware
forcing an LCALL to the appropriate vector address, if the
following conditions are met:
• No interrupt of equal or higher priority is already in
progress.
• An instruction is currently being executed and is not
completed.
• The instruction in progress is not RETI or any write
access to the registers IEN0, IEN1, IEN2, IP0 or IP1.
The following SFR registers control the interrupt functions:
• The interrupt enable registers: IEN0, IEN1 and IEN2.
• The Timer/Counter control registers, TCON and
T2CON.
• Theinterruptrequestregister,IRCON.
• The interrupt priority registers: IP0 and IP1.
Table 8. Timers/Counters Mode Description
M1 M0 MODE FUNCTION
0 0 Mode 0
13-bit Counter/Timer mode with 5 lower bits in the TL0 or TL1 register and the remaining 8 bits
in the TH0 or TH1 register (for Timer 0 and Timer 1, respectively). The 3 high order bits of TL0
and TL1 are held at zero.
0 1 Mode 1 16-bit Counter/Timer mode.
1 0 Mode 2 8-bit auto-reload Counter/Timer. The reload value is kept in TH0 or TH1, while TL0 or TL1 is
incremented every machine cycle. When TLxoverows,avaluefromTHx is copied to TLx.
1 1 Mode 3 If Timer 1 M1 and M0 bits are set to 1, Timer 1 stops.
If Timer 0 M1 and M0 bits are set to 1, Timer 0 acts as two independent 8-bit Timer/Counters.
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Table 10. Flash Banks
enabling the CE, the MPU copies these images to their
respective locations.
Flash space allocated for the CE program is limited to
4096 16-bit words (8KB). The CE program must begin
on a 1KB boundary of the flash address space. The
CE_LCTN[6:0] (71M6541GT/42GT) or CE_LCTN[5:0]
(71M6541DT/41FT/42FT) field defines where in flash
the CE code resides. The address of the CE program is
0bXXXX XX00 0000 0000, where XXXX XX represents
one of the 64 1KB pages at which the CE program begins.
The program memory of the 71M6541GT/71M6542GT
consists of a fixed lower bank area of 32 kB addressable
at 0x0000 to 0x7FFF plus an upper bank area of 32 kB,
addressable at 0x8000 to 0xFFFF. The upper bank area
is banked using the I/O RAM FLSH_BANK register as
follows.NotethatwhenFLSH_BANK[1:0]=00,theupper
bank area is the same as the lower bank area (Table 10).
The flash memory page address register FLSH_
PGADR[6:0] (SFR B7[7:1]) points to an address in the
71M6541GT/71M6542GT program address space. This
address in the 71M6541GT/71M6542GT program address
space can refer to different flash memory addresses,
depending on the setting of the FLSH_BANK[1:0] bits.
The CE location register (CE_LCTN[6:0]), on the other
External MPU Interrupts
The seven external interrupts are the interrupts external
to the 80515 core, i.e., signals that originate in other
parts of the 71M654xT, for example the CE, DIO, RTC, or
EEPROM interface.
The polarity of interrupts 2 and 3 is programmable in
the MPU via the I3FR and I2FR bits in T2CON (SFR
0xC8). Interrupts 2 and 3 should be programmed for
fallingsensitivity(I3FR=I2FR=0).Thegeneric8051
MPU literature states that interrupts 4 through 6 are
defined as rising-edge sensitive. Thus, the hardware
signals attached to interrupts 5 and 6 are inverted to
achieve the edge polarity shown in Table 9.
External interrupt 0 and 1 can be mapped to pins on the
device using DIO resource maps.
On-Chip Resources
Flash Memory
The device includes 128KB (71M6541GT, 71M6542GT)
64KB (71M6541FT, 71M6542FT) or 32KB (71M6541DT)
of on-chip flash memory. The flash memory primarily con-
tains MPU and CE program code. It also contains images
of the CE RAM and I/O RAM. On power-up, be fore
Table 9. External MPU Interrupts
FLSH_BANK[1:0] ADDRESS RANGE FOR LOWER BANK
(0x0000–0x7FFF)
ADDRESS RANGE FOR UPPER BANK
(0x8000–0x7FFF)
00 0x0000–0x7FFF 0x0000–0x7FFF
01 0x0000–0x7FFF 0x8000–0x7FFF
10 0x0000–0x7FFF 0x10000–0x17FFFF
11 0x0000–0x7FFF 0x18000–0x1FFFF
EXTERNAL
INTERRUPT CONNECTION POLARITY FLAG
RESET
0 Digital I/O (IE0) Programmable Automatic
1 Digital I/O (IE1) Programmable Automatic
2CE_PULSE(IE_XPULSE,IE_YPULSE,IE_WPULSE,IE_VPULSE) Rising Manual
3CE_BUSY(IE3) Falling Automatic
4 VSTAT (VSTAT[2:0] changed) (IE4) Rising Automatic
5EEPROMbusy(falling),SPI(rising)(IE_EEX,IE_SPI) — Manual
6XFER_BUSY(falling),RTC_1SEC,RTC_1MIN,RTC_T,TC_TEMP
(IE_XFER,IE_RTC1S,IE_RTC1M,IE_RTCT) Falling Manual
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hand, points directly to an address in the flash memory
andisnotaffectedbytheFLSH_BANK[1:0]bits.
When the SECURE bit (SFR B2[6]) is set to a 1,
page erase of certain flash memory pages is blocked.
These pages are page 0 (flash memory address range
0x00000–0x003FF) and all pages between the start of the
CEprogram(CE_LCTN[6:0])andflashmemoryaddress
0x1FFFF.
While operating in SPI Flash Mode (SFM), SPI single-
bytetransactionsareusedtowritetoFLSH_BANK[1:0].
During an SPI single-byte transaction, SPI_CMD[1:0]
overwritesthecontentsofFLSH_BANK[1:0].Thisallows
for access of the entire 128KB Flash memory while oper-
ating in SFM on the 71M6541GT/71M6542GT.
Flash memory can be accessed by the MPU and the CE
for reading, and by the SPI interface for reading or writing.
MPU/CE RAM
The 71M6541DT includes 3KB of static RAM memory on-
chip (XRAM) plus 256 bytes of internal RAM in the MPU
core. The 71M6541FT/GT and the 71M6542FT/GT include
5KB of static RAM memory on-chip (XRAM) plus 256
bytes of internal RAM in the MPU core. The static RAM
is used for data storage for both MPU and CE operations.
I/O RAM
The I/O RAM can be seen as a series of hardware reg-
isters that control basic hardware functions. I/O RAM
address space starts at 0x2000.
The 71M6541DT/FT/GT and 71M6542FT/GT include 128
bytes NV RAM memory on-chip in the I/O RAM address
space (addresses 0x2800 to 0x287F). This memory sec-
tion is supported by the voltage applied at VBAT_RTC and
the data in it are preserved in BRN, LCD, and SLP modes
as long as the voltage at VBAT_RTC is within specification.
Crystal Oscillator
The oscillator drives a standard 32.768kHz tuning-fork
crystal. This type of crystal is accurate and does not
require a high-current oscillator circuit. The oscillator
power dissipation is very low to maximize the lifetime of
the VBAT_RTC battery.
Oscillator calibration can improve the accuracy of both the
RTC and metering.
PLL
Timing for the device is derived from the 32,768Hz crystal
oscillator. The oscillator output is routed to a phase-locked
loop (PLL). The PLL multiplies the crystal frequency by
600toproduceastable19.6608MHzclockfrequency.This
is the master clock (MCK), and all on-chip timing, except
for the RTC clock, is derived from MCK.
The master clock can operate at either 19.66MHz or
6.29MHz depending on the PLL_FAST bit. The MPU
clockfrequencyCKMPUisdeterminedbyanotherdivider
controlledbytheI/ORAMcontrolfieldMPU_DIV[2:0]and
can be set to MCK x 2-(MPU_DIV+2),whereMPU_DIV[2:0]
may vary from 0 to 4. The 71M654xT VV3P3SYS supply
currentisreducedbyreducingtheMPUclockfrequency.
WhentheICE_Epinishigh,thecircuitalsogeneratesthe
9.83MHz clock for use by the emulator.
The two general-purpose counter/timers contained in the
MPU are clocked by CKMPU.
The PLL is only turned off in SLP mode.
When the part is waking up from SLP or LCD modes,
the PLL is turned on in 6.29MHz mode, and the PLL fre-
quencyisnotbeaccurateuntilthePLL_OKflagbecomes
active. Due to potential overshoot, the MPU should not
changethevalueofPLL_FASTuntilPLL_OKistrue.
Real-Time Clock (RTC)
The real-time clock is driven directly by the crystal
oscillator and is powered by either the VV3P3SYS pin
or the VBAT_RTC pin, depending on the V3OK internal
bit. The RTC consists of a counter chain and a set of
output registers. The counter chain consists of registers
for seconds, minutes, hours, day of week, day of month,
month, and year. The chain registers are supported by a
shadow register that facilitates read and write operations.
RTC Trimming
The RTC accuracy can be trimmed by using either of two
trimming mechanisms. The first is an analog rate adjust-
ment, RTCA_ADJ[6:0]. This adjustment changes the
crystalfrequency(andthusthetimebasefortheentire
SOC) by slightly varying the crystal load capacitance.
The second adjustment is a digital trimming mechanism
that affects only the RTC. Either or both of these adjust-
ment mechanisms can be used to trim the RTC.
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The 71M6541DT/FT/GT and 71M6542FT/GT can also be
configured to regularly measure die temperature, includ-
ing in SLP and LCD modes and while the MPU is halted.
If enabled, the temperature information is automatically
used to correct for the temperature variation of the crystal.
Aquadraticequationisusedtocomputethetemperature
correction factors.
Thetemperatureispassedbothtothequadraticcalcula-
tion block and to a range check block. If the temperature
exceeds the limits established in the SMIN, SMAX and
SFILT registers a WAKE or an INTERRUPT event is
posted.
Thequadraticcalculationblockcomputesthepositionon
the inverse parabolic curve that is characteristic for tuning
forkcrystalsbasedontheknownαandT0 values for the
crystal (these are published by the crystal manufacturer
and are relatively consistent for a particular crystal type).
Finally,theabsolutefrequencyerrorisaddedorsubtract-
ed from the computed value, and the final result is used
tocompensatethefrequencyofthecrystal.
RTC Interrupts
The RTC generates interrupts each second and each
minute. These interrupts are called RTC_1SEC and
RTC_1MIN.Inaddition, the RTCfunctionsas an alarm
clock by generating an interrupt when the minutes and
hoursregistersbothequaltheirrespectivetargetcounts
as defined in the alarm registers. The alarm clock inter-
rupt is called RTC_T.All three interrupts appear in the
MPU’s external interrupt 6.
Temperature Sensor
The 71M654xT includes an on-chip temperature sensor
for determining the temperature of its bandgap re ference.
The primary use of the temperature data is to determine
themagnitudeofcompensationrequiredtooffsetthether-
mal drift in the system for the compensa tion of current,
voltage and energy measurement and the RTC. See the
Metrology Temperature Compensation.
The 71M654xT uses a dual-slope temperature measure-
menttechniquethatisoperationalinSLPandLCDmode,
as well as BRN and MSN modes. This means that the
temperature sensor can be used to compensate for the
frequencyvariationofthecrystal,eveninSLPmodewhile
the MPU is halted.
In MSN and BRN modes, the temperature sensor is
awakened on command from the MPU by setting the
TEMP_START control bit. The MPU must wait for the
TEMP_START bit to clear before reading STEMP[15:0]
andbeforesettingtheTEMP_STARTbitonceagain.In
SLP and LCD modes, it is awakened at a regular rate set
byTEMP_PER[2:0].
The result of the temperature measurement can be read
from STEMP[15:0]. Typically, only eleven bits are signifi-
cant, the remaining high-order bits reflecting the sign of
the temperature relative to 0C.
Battery Monitor
The 71M654xT temperature measurement circuit can
also monitor the batteries at the VBAT and VBAT_RTC
pins. The battery to be tested (i.e., VBAT or VBAT_RTC
pin)isselectedbyTEMP_BSEL.
Figure 8. Typical LCD Waveforms
STATIC (LCD_MODE=100)
COM0
COM1
COM2
COM3
COM4
COM5
SEG_ON
SEG_OFF
(1/2)
(1/2)
(1/2)
(1/2)
(1/2)
1/3 BIAS, 3 STATES (LCD_MODE = 011 )
COM0
COM1
COM2
COM3
COM4
COM5
SEG_ON
SEG_OFF
(2/3)
012
(1/3)
1/2 BIAS, 3 STATES (LCD_MODE = 011 )
COM0
COM1
COM2
COM3
COM4
COM5
SEG_ON
SEG_OFF
(1/2)
(1/2)
(1/2)
012
1/3 BIAS, 6 STATES (LCD_MODE = 110 )
COM0
COM1
COM2
COM3
COM4
COM5
SEG_ON
SEG_OFF
012345
1/2 BIAS, 2 STATES (LCD_MODE = 010 )
COM0
COM1
COM2
COM3
COM4
COM5
SEG_ON
SEG_OFF
(1/2)
(1/2)
(1/2)
(1/2)
01
1/3 BIAS, 4 STATES (LCD_MODE = 000 )
COM0
COM1
COM2
COM3
COM4
COM5
SEG_ON
SEG_OFF
0123
T
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When TEMP_BAT is set, a battery measurement is
performed as part of each temperature measurement.
The value of the battery reading is stored in register
BSENSE[7:0]. The battery voltage can be calculated by
computing BSENSE/42.7.
In MSN mode, a 100µA de-passivation load can be applied
totheselectedbattery(i.e.,selectedbytheTEMP_BSEL
bit) by setting the BCURR bit. Battery impedance can
be measured by taking a battery measurement with and
without BCURR. Regardless of the BCURR bit setting,
the battery load is never applied in BRN, LCD, and SLP
modes.
Digital I/O and LCD Segment Drivers
The 71M6541DT/FT/GT and 71M6542FT/GT combine
most DIO pins with LCD segment drivers. Each SEG/
DIO pin can be configured as a DIO pin or as a segment
(SEG) driver pin.
On reset or power-up, all DIO pins are DIO inputs until
they are configured as desired under MPU control. The
pin function can be configured by the I/O RAM registers
LCD_MAPn. Setting the bit corresponding to the pin
in LCD_MAPn to 1 configures the pin for LCD, setting
LCD_MAPnto0configuresitforDIO.
Once a pin is configured as DIO, it can be configured
independently as an input or output. The PB pin is a dedi-
cated digital input and is not part of the SEGDIO system.
Some pins (SEGDIO2 through SEGDIO11 and PB) can
be routed to internal logic such as the interrupt control-
ler or a timer channel. This routing is independent of the
direction of the pin, so that outputs can be configured to
cause an interrupt or start a timer.
A total of 32 combined SEG/DIO pins plus 5 SEG outputs
are available for the 71M6541DT/FT/GT. These pins can
be categorized as follows:
17 combined SEG/DIO segment pins:
• SEGDIO4…SEGDIO5 (2 pins)
• SEGDIO9…SEGDIO14 (6 pins)
• SEGDIO19…SEGDIO25 (7 pins)
• SEGDIO44…SEGDIO45 (2 pins)
15 combined SEG/DIO segment pins shared with other
functions:
• SEGDIO0/WPULSE, SEGDIO1/VPULSE (2 pins)
• SEGDIO2/SDCK, SEGDIO3/SDATA (2 pins)
• SEGDIO6/XPULSE, SEGDIO7/YPULSE (2 pins)
• SEGDIO8/DI (1 pin)
• SEGDIO26/COM5, SEGDIO27/COM4 (2 pins)
• SEGDIO36/SPI_CSZ…SEGDIO39/SPI_CKI(4pins)
• SEGDIO51/OPT_TX,SEGDIO55/OPT_RX(2pins)
5 dedicated SEG segment pins are available:
• ICEIntefacepins:SEG48/E_RXTX,SEG49/E_TCLK,
SEG50/E_RST(3pins)
• Test Port pins: SEG46/TMUX2OUT, SEG47/TMUXOUT
(2 pins)
There are four dedicated common segment outputs
(COM0…COM3) plus the two additional shared common
segment outputs that are listed under combined SEG/DIO
shared pins (SEGDIO26/COM5, SEGDIO27/COM4).
Thus, in a configuration where none of these pins are
used as DIOs, there can be up to 37 LCD segment pins
with 4 commons, or 35 LCD segment pins with 6 com-
mons. And in a configuration where LCD segment pins
are not used, there can be up to 32 DIO pins.
LCD Drivers
The LCD drivers are grouped into up to six commons
(COM0 – COM5) and up to 56 segment drivers. The
LCD interface is flexible and can drive 7-segment digits,
14-segments digits or annunciator symbols.
LCD voltage can be taken from the VLCD pin or the
VV3P3SYS pin. A contrast DAC regulates VLCD from
either VBAT or VV3P3SYS.
The LCD system has the ability to drive up to six seg-
ments per SEG driver. If the display is configured with six
back planes, the 6-way multiplexing minimizes the num-
ber of SEG pins required to drive a display. This maxi-
mizes the number of DIO pins available to the application.
If 5-state multiplexing is selected, SEGDIO27 is converted
to COM4. If 6-state multiplexing is selected, SEGDIO26 is
converted to COM5.
TheLCD_ONandLCD_BLANKbitsareaneasywayto
either blank the LCD display or to turn all segments on.
Neither bit affects the contents of the LCD data stored in
theLCDSEG_DIO[]registers.Incomparison,LCD_RST
(I/ORAM0x240C[2])clearsallLCDdatatozero.LCD_
RST affects only pins that are configured as LCD.
The LCD can be driven in static, ½ bias, and ⅓ bias
modes. Note that COM pins that are not required in a
specific mode maintain a ‘segment off’ state rather than
GND, VCC, or high impedance.
The segment drivers SEGDIO22 and SEGDIO23 can be
configured to blink at either 0.5 Hz or 1 Hz. The blink rate
iscontrolledbyLCD_Y.Therecanbeuptosixsegments
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connected to each of these driver pins. The I/O RAM fields
LCD_BLKMAP22[5:0]andLCD_BLKMAP23[5:0]identify
which pixels, if any, are to blink. LCD_BLKMAP22[5:0]
andLCD_BLKMAP23[5:0]arenonvolatile.
The LCD bias may be compensated for temperature
usingtheLCD_DAC[4:0]field.Thebiasmaybeadjusted
from 1.4 V below the 3.3 V supply (VV3P3SYS in MSN
mode and VBAT in BRN and LCD modes). When the
LCD_DAC[4:0]fieldissetto000,theDACisbypassed
and powered down. This can be used to reduce current
in LCD mode.
The 71M6541DT/FT/GT has 35 LCD driver pins available,
and can drive up to 210 segments. The 71M6542FT/GT
has 56 LCD driver pins available, and can drive up to 336
segments.
Square Wave Output
The 71M654xT includes a square wave generator that
can be configured to present a square wave on the
SEGDIO15pin.Thissquarewavecanbeusedasaclock
to drive other devices and peripherals.
TheoutputisenabledbysettingtheOUT_SQEbit.The
output frequency can then be selected by setting the
OUT_SQ[1:0]bits.
EEPROM Interface
The 71M654xT provides hardware support for both two-
pin (I2C) and three-wire (MICROWIRE) EEPROMs.
Two-Pin EEPROM Interface
The two-pin serial interface is multiplexed onto the
SEGDIO2 (SDCK) and SEGDIO3 (SDATA) pins. Configure
theinterfacefortwo-pinmodebysettingDIO_EEX[1:0]=
01. The MPU communicates with the interface through
the SFR registers EEDATA and EECTRL. To write a
byte of data to the EEPROM the MPU places the data in
EEDATA and then writes the Transmit code to EECTRL.
This initiates the transmit operation which is finished
when the BUSY bit falls. INT5 is also asserted when
BUSYfalls.TheMPUcanthenchecktheRX_ACKbitto
see if the EEPROM acknowledged the trans mission.
A byte is read by writing the Receive command to EECTRL
and waiting for the BUSY bit to fall. Upon completion,
the received data is in EEDATA. The serial transmit and
receive clock is 78kHz during each transmission, and then
holds in a high state until the next transmission.
The two-pin interface handles protocol details. The MPU
can command the interface to issue a start, a repeated
start and a stop condition, and it can manage the transmit-
ted ACK status as well.
Three-Wire EEPROM Interface
The three-wire interface supports standard MICROWIRE
(single data pin with clock and select pins) or a subset of
SPI (separate DI and DO pins with clock and select pins).
MICROWIREisselectedbysettingDIO_EEX[1:0]=10.
In this mode, EECTRL selects whether the interface is
sending or receiving, and eight bits of data are transferred
in each transaction. In this configuration, SEGDIO2 is
configured for clock, and SEGDIO3 is configured for data.
WhenseparateDI/DOpinsareselected(DIO_EEX[1:0]
= 11) the interface operates as a subset of SPI. Only
SPI modes 0 or 3 are supported. In this configuration,
SEGDIO3 is DO and SEGDIO8 is DI.
UART
The 71M6541DT/FT/GT and 71M6542FT/GT include a
UART (UART0) that can be programmed to communicate
with a variety of AMR modules and other external devices.
A second UART (UART1) is connected to the optical port.
The 80515 only supports two UARTs, but meters occa-
sionally need three. The 71M654xT tries to help in two
ways.
First, as shown in Figure 9, the 71M654xT can be config-
ured to switch the optical UART to DIOs 5 and 17 by set-
tingUMUX_SEL(I/ORAM0x2456[4])to1.Thisisuseful
when a conventional UART can appear by command at
different pins. The DIOs must not be configured as LCD
outputs.
Also, as shown in Figure 9, the 71M654xT can also be
configured to drive the optical UART with DIO signal in a
bitbangedconfiguration.WhencontrolbitOPT_BB(I/O
RAM 0x2022[0]) is set, the optical port is driven by DIO5
andtheSEGDIO5pinisdrivenbyUART1_TX.Thiscon-
figuration is typically used when the two dedicated UARTs
must be connected to high speed clients and a slower
optical UART is permissible.
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Figure 9. Optical Interface (UART1)
SPI Slave Port
The SPI slave port communicates directly with the MPU
data bus and is able to read and write Data RAM and
I/O RAM locations. It is also able to send commands to
the MPU. The interface to the slave port consists of the
SPI_CSZ, SPI_CKI, SPI_DI and SPI_DO pins. These
pins are multi plexed with the combined DIO/LCD segment
driver pins SEGDIO36 to SEGDIO39.
Additionally, the SPI interface allows flash memory to
be read and to be programmed. To facilitate flash pro-
gramming, cycling power or asserting RESET causes
the SPI port pins to default to SPI mode. The SPI port is
disabledbyclearingtheSPI_Ebit.
Possible applications for the SPI interface are:
• An external host reads data from CE locations to
obtain metering information. This can be used in
applications where the 71M654xT function as a smart
front-end with preprocessing capability. Since the
addresses are in 16-bit format, any type of XRAM data
can be accessed: CE, MPU, I/O RAM, but not SFRs or
the 80515-internal register bank.
• A communication link can be established through the
SPI interface: By writing into MPU memory locations,
the external host can initiate and control processes in
the 71M654xT MPU. Writing to a CE or MPU location
normally generates an interrupt, a function that can be
used to signal to the MPU that the byte that had just
been written by the external host must be read and
processed. Data can also be inserted by the external
host without generating an interrupt.
• An external DSP can access front-end data gener-
ated by the ADC. This mode of operation uses the
71M654xT as an analog front-end (AFE).
• Flash programming by the external host (SPI Flash
Mode).
SPI Safe Mode
Sometimes it is desirable to prevent the SPI interface
from writing to arbitrary RAM locations and thus disturb-
ing MPU and CE operation. This is especially true in AFE
applications. For this reason, the SPI SAFE mode was
created. In SPI SAFE mode, SPI write operations are
disabled except for a 16 byte transfer region at address
1
SEG17 INTERNAL
LCD_SEGDIO17 = 2
LCD_MAP[17]
SEGDIO17
0
1
SEG16
LCD_SEGDIO16 = 0
LCD_MAP[16]
SEGDIO16
0
0
0
1
1
UART1_TX
DIO17
0
0
1
1
0
1
1
UART1_RX
1
SEG55
LCD_MAP[55]
SEGDIO55/
OPT_RX
V3P3
0
1
DIO55
OPT_RXINV
OPT_RXDIS
VARPULSE 3
0
1
SEG51
LCD_MAP[51]
WPULSE 2
DIO51 0
OPT_TXE[1:0]
BA
EN
OPT_TXMOD
OPT_FDC
2
OPT_TXINV
DUTY
MOD 1
OPT_TX
0
1
SEG5
LCD_MAP[5]
OPT_TXMOD = 1
OPT_FDC = 2 (25%)OPT_TXMOD = 0
1/38kHz
A
B
UMUX_SEL
UART1_TX
1
0
1
UART1_TX
DIO5
OPT_BB
SEGDIO5/TX2
0
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0x400 to 0x40F. If the SPI host needs to write to other
addresses,itmustusetheSPI_CMDregistertorequest
the write operation from the MPU. SPI SAFE mode is
enabledbytheSPI_SAFEbit.
SPI Flash Mode (SFM)
In normal operation, the SPI slave interface cannot read
or write the flash memory. However, the 71M6541DT/
FT/GT and 71M6542FT/GT support an SPI Flash Mode
(SFM) which facilitates initial programming of the flash
memory. When in SFM mode, the SPI can erase, read,
and write the flash memory. Other memory elements such
as XRAM and I/O RAM are not accessible in this mode. In
order to protect the flash contents, several operations are
requiredbeforetheSFMmodeissuccessfullyinvoked.
In SFM mode, n byte reads and dual-byte writes to flash
memory are supported. Since the flash write operation is
always based on a two-byte word, the initial address must
always be even. Data is written to the 16-bit flash memory
bus after the odd word is written.
While operating in SPI flash mode (SFM), SPI single-
bytetransactionsareusedtowritetoFLSH_BANK[1:0].
During an SPI single-byte transaction, SPI_CDMI[1:0]
overwritesthecontentsofFLSH_BANK[1:0].Thisallows
access to the entire 128KB flash memory while operating
in SFM on the 71M6541GT/71M6542GT.
In SFM mode, the MPU is completely halted. The
71M6541DT/FT/GT and 71M6542FT/GT must be reset
by the WD timer or by the RESET pin in order to exit SFM
mode. If the SPI port is used for code updates (in lieu of
a programmer that uses the ICE port), then a code that
disables the flash access through SPI can potentially lock
out flash program updates.
Hardware Watchdog Timer
An independent, robust, fixed-duration, watchdog
timer (WDT) is included in the 71M6541DT/FT/GT and
71M6542FT/GT. It uses the RTC crystal oscillator as its
time base and must be refreshed by the MPU firmware at
least every 1.5 seconds. When not re freshed on time, the
WDT overflows and the part is reset as if the RESET pin
were pulled high, except that the I/O RAM bits are in the
same state as after a wake-up from SLP or LCD modes.
After 4100 CK32 cycles (or 125 ms) following the WDT
overflow, the MPU is launched from program address
0x0000.
The watchdog timer is also reset when the internal signal
WAKE=0.
Test Ports
Two independent multiplexers allow the selection of
internal analog and digital signals for the TMUXOUT and
TMUX2OUT pins. These pins are multiplexed with the
SEG47 and SEG46 function. In order to function as test
pins,LCD_MAP[46]andLCD_MAP[47]mustbe0.(See
Table 11)
The TMUXOUT and TMUX2OUT pins may be used for
diagnostics purposes during the product development
cycle or in the production test. The RTC 1-second output
may be used to calibrate the crystal oscillator. The RTC
4-second output provides higher precision for RTC cali-
bration. RTCLK may also be used to calibrate the RTC.
Table 11. Test Ports
TMUX[5:0] SIGNAL NAME DESCRIPTION
1 RTCLK 32.768 kHz clock waveform
9WD_RST Indicates when the MPU has reset the watchdog timer. Can be monitored to determine
spare time in the watchdog timer.
A CKMPU MPU clock
D V3AOK bit
IndicatesthattheV3P3Apinvoltageis≥3.0V.TheV3P3AandV3P3SYSpinsare
expected to be tied together at the PCB level. The 71M6543 monitors the V3P3A pin
voltage only.
E V3OK bit
IndicatesthattheV3P3Apinvoltageis≥2.8V.TheV3P3AandV3P3SYSpinsare
expected to be tied together at the PCB level. The 71M654 monitors the V3P3A pin
voltage only.
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Table 11. Test Ports (continued)
TMUX[5:0] SIGNAL NAME DESCRIPTION
1 RTCLK 32.768 kHz clock waveform
1B MUX_SYNC Internal multiplexer frame SYNC signal.
1C CE_BUSYinterrupt
1D CE_XFERinterrupt
1F RTM output from
CE
Note: All TMUX[5:0] values that are not shown are reserved.
TMUX2[4:0] SIGNAL NAME DESCRIPTION
0WD_OVF Indicateswhenthewatchdogtimerhasexpired(overowed).
1PULSE_1S
One-second pulse with 25% duty cycle. This signal can be used to measure the deviation
of the RTC from an ideal 1-second interval. Multiple cycles should be averaged together
tolteroutjitter.
2PULSE_4S
Four-second pulse with 25% duty cycle. This signal can be used to measure the deviation
of the RTC from an ideal 4-second interval. Multiple cycles should be averaged together
tolteroutjitter.Thispulseprovidesamoreprecisemeasurementthanthe1-second
pulse.
3 RTCLK 32.768 kHz clock waveform
8SPARE[1] bit – I/O
RAM 0x2704[1] Copies the value of the bit stored in 0x2704[1]. For general purpose use.
9SPARE[2] bit – I/O
RAM 0x2704[2] Copies the value of the bit stored in 0x2704[2]. For general purpose use.
A WAKE Indicates when a WAKE event has occurred.
BMUX_SYNC Internal multiplexer frame SYNC signal.
C MCK
E GNDD Digital GND. Use this signal to make the TMUX2OUT pin static.
12 INT0 – DIG I/O
Interrupts
13 INT1 – DIG I/O
14 INT2–CE_PULSE
15 INT3–CE_BUSY
16 INT4 – VSTAT
17 INT5 – EEPROM/
SPI
18 INT6 – XFER, RTC
1F RTM_CK(ash)
Note: All TMUX2[4:0] values which are not shown are reserved.
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Figure 10. Waveforms Comparing Voltage, Current, Energy per Interval, and Accumulated Energy
Functional Description
Theory of Operation
The energy delivered by a power source into a load can
be expressed as:
t
0
E V(t)I(t)dt=∫
Assuming phase angles are constant, the following for-
mulae apply:
• P=RealEnergy[Wh]=VxAxcos(φ)xt
• Q=ReactiveEnergy[VARh]=VxAxsin(φ)xt
• S=ApparentEnergy[VAh]=
22
PQ
+
For a practical meter, not only voltage and current ampli-
tudes, but also phase angles and harmonic content may
change constantly. Thus, simple RMS measurements are
inherently inaccurate. The 71M654xT, however, functions
by emulating the integral operation above by processing
current and voltage samples at a constant rate. As long
as the ADC resolution is high enough and the sample fre-
quencyisbeyondtheharmonicrangeofinterest,thecur-
rent and voltage samples, multiplied by the sample period
yield an accurate value for the instantaneous energy.
Summingtheinstantaneousenergyquantitiesovertime
provides accurate results for accumulated energy.
The application of 240V AC and 100A results in an accu-
mulationof480Ws(=0.133Wh)overthe20msperiod,as
indicated by the accumulated power curve. The described
sampling method works reliably, even in the presence of
dynamic phase shift and harmonic distortion.
Battery Modes
The 71M654xT can operate in one of four power modes:
mission (MSN), brownout (BRN), sleep (SLP), or LCD-
only (LCD) mode.
Shortly after system power (VV3P3SYS) is applied, the
part is in mission mode. MSN mode means that the part
is operating with system power and that the internal PLL
is stable. This mode is the normal operating mode where
the part is capable of measuring energy.
When system power is not available, the 71M654xT is in
one of three battery modes: BRN, SLP or LCD.
An internal comparator monitors the voltage at the
VV3P3SYS pin (note that VV3P3SYS and VV3P3A are
-500
-400
-300
-200
-100
0
100
200
300
400
500
0510 15 20
TIME (ms)
V(V), I(A), P(Ws)
VOLTAGE (V)
CURRENT (A)
ENERGY PER INTERVAL (Ws)
ACCUMULATED ENERGY (Ws)
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typically connected together at the PCB level). When
the VV3P3SYS dc voltage drops below 3.0 VDC, the
comparator resets an internal power status bit called
V3OK. As soon as system power is removed and V3OK
=0,the71M654xTswitchestobatterypower(VBAT pin),
notifies the MPU by issuing an interrupt and updates the
VSTAT[2:0] register. The MPU continues to execute code
when the system transitions from MSN to BRN mode.
Depending on the MPU code, the MPU can choose
to stay in BRN mode, or transition to LCD or to SLP
mode. BRN mode is similar to MSN mode except that
resources powered by VV3P3A power, such as the ADC
are inaccurate. In BRN mode the CE continues to run
and should be turned off to conserve VBAT power. Also,
thePLLcontinuestofunctionatthesamefrequencyasin
MSNmodeanditsfrequencyshouldbereducedtosave
power.
When system power is restored, the 71M654xT
automatically transitions from any of the battery modes
(BRN, LCD, SLP) back to MSN mode, switches back
to using system power (VV3P3SYS, VV3P3A), issues an
interrupt and updates VSTAT[1:0]. The MPU software
should restore MSN mode operation by issuing a soft
reset to restore system settings to values appropriate for
MSN mode.
Transitions from both LCD and SLP mode to BRN mode
can be initiated by the following events:
1) Wake-up timer timeout.
2) Pushbutton (PB) is activated.
3) A rising edge on SEGDIO4, SEGDIO52 (71M6542FT/
GT only) or SEGDIO55.
4) ActivityontheRXorOPT_RXpins.
Brownout Mode
In BRN mode, most nonmetering digital functions are
active including ICE, UART, EEPROM, LCD and RTC. In
BRN mode, the PLL continues to function at the same fre-
quencyasMSNmode.ItisuptotheMPUtoreducethe
PLLfrequencyortheMPUfrequencyinordertominimize
power consumption.
From BRN mode, the MPU can choose to enter LCD or
SLP modes. When system power is re stored while the
71M654xT is in BRN mode, the part automatically transi-
tions to MSN mode.
LCD Only Mode
LCD mode may be commanded by the MPU at any time
bysettingtheLCD_ONLYcontrolbit.However,itisrec-
ommendedthattheLCD_ONLYcontrolbitbesetbythe
MPU only after the 71M654xT has entered BRN mode.
For example, if the 71M654xT is in MSN mode when
LCD_ONLYisset,thedurationofLCDmodeisverybrief
and the 71M654xT immediately ‘wakes’.
In LCD mode, VV3P3D is disabled, thus removing all
current leakage from the VBAT pin. Before asserting
LCD_ONLY mode, it is recommended that the MPU
minimizePLLcurrentbyreducingtheoutputfrequencyof
thePLLto6.2MHz(i.e.,writePLL_FAST=0).
InLCDmode,thedatacontainedintheLCD_SEGregistersis
displayed using the segment driver pins. Up to two LCD seg-
ments connected to the pins SEGDIO22 and SEGDIO23 can
be made to blink without the involvement of the MPU, which
is disabled in LCD mode. To minimize battery power con-
sumption, only segments that are used should be enabled.
After the transition from LCD mode to MSN or BRN mode,
the PC (Program Counter) is at 0x0000, the XRAM is in
an undefined state, and configuration I/O RAM bits are
reset (see Table 13 for I/O RAM state upon wake). The
data stored in nonvolatile I/O RAM locations is preserved
in LCD mode (the shaded locations in Table 12 are non-
volatile).
Sleep Mode
When the VV3P3SYS pin voltage drops below 2.8 VDC,
the 71M654xT enters BRN mode and the VV3P3D pin
obtains power from the VBAT pin instead of the VV3P3SYS
pin. Once in BRN mode, the MPU may invoke SLP mode
by setting the SLEEP bit. The purpose of SLP mode is to
consume the least amount power while still maintaining
the real time clock, temperature compensation of the
RTC, and the nonvolatile portions of the I/O RAM.
In SLP mode, the VV3P3D pin is disconnected, removing
all sources of current leakage from the VBAT pin. The
nonvolatile I/O RAM locations and the SLP mode functions,
such as the temperature sensor, oscillator, RTC, and the
RTC temperature compensation are powered by the
VBAT_RTC pin. SLP mode can be exited only by a system
power-up event or one of the wake methods.
If the SLEEP bit is asserted when VV3P3SYS pin power is
present (i.e., while in MSN mode), the 71M654xT enters
SLP mode, resetting the internal WAKE signal, at which
point the 71M654xT begins the standard wake from sleep
procedures.
When power is restored to the VV3P3SYS pin, the
71M654xT transitions from SLP mode to MSN mode and
the MPU PC (Program Counter) is initialized to 0x0000.
At this point, the XRAM is in an undefined state, but
nonvolatile I/O RAM locations are preserved.
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Applications Information
Connecting 5V Devices
All digital input pins of the 71M654xT are compatible with
external 5V devices. I/O pins configured as inputs do not
requirecurrent-limitingresistorswhentheyareconnected
to external 5V devices.
Direct Connection of Sensors
The 71M654xT supports direct connection of current
transformer and shunt-fed sensors.
Using the 71M6541DT/FT/GT with Local Sensors
The 71M6541DT/FT/GT can be configured to operate
with locally connected current sensors (Figure 15). The
IAP-IAN current channel may be directly connected to
either a shunt resistor or a CT, while the IBP-IBN channel
is connected to a CT and is therefore isolated. This con-
figuration implements a single-phase measurement with
tamper-detection using one current sensor to measure
the neutral current. This configuration can also be used to
create a split phase meter (ANSI Form 2S). For best per-
formance, both the IAP-IAN and IBP-IBN current sensor
inputs are configured for differential mode. The IBP-IBN
input must be configured as an analog differential input
disablingtheremotesensorinterface(RMT_E=0).
Using the 71M6541DT/FT/GT with Remote Sensors
The 71M6541DT/FT/GT can be configured to operate with
71M6x01 remote sensor interfaces and current shunts
(Figure 16). This configuration implements a single-phase
measurement with tamper-detection using the second
current sensor. This configuration can also be used to
create a split phase meter (ANSI Form 2S). For best per-
formance, the IAP-IAN current sensor input is configured
for differential mode (DIFFA_E = 1). The outputs of the
71M6x01 isolated sensor interface are routed through a
pulse transformer, which is connected to the pins IBP-IBN.
The IBP-IBN pins must be configured for remote sensor
communication(i.e.,RMT_E=1).
Using the 71M6542FT/GT with Local Sensors
The 71M6542FT/GT can be configured to operate with
locally connected current sensors (Figure 17). The IAP-
IAN current channel may be directly connected to either a
shunt resistor or a CT, while the IBP-IBN channel is con-
nected to a CT and is therefore isolated. This configuration
implementsadual-phasemeasurementutilizingEquation
2. For best performance, both the IAP-IAN and IBP-IBN
current sensor inputs are configured for differential mode.
The IBP-IBN input must be configured as an analog
differential input disabling the remote sensor interface
(RMT_E=0).
Using the 71M6542FT/GT with Remote Sensors
The 71M6541FT/GT can be configured to operate with
71M6x01 remote sensor interfaces and current shunts for
two-phase operation (Figure 18). For best performance,
the IAP-IAN current sensor input is configured for differ-
entialmode(DIFFA_E=1).Theisolatedsensorinterface
isolates phase B. The outputs of the 71M6x01 isolated
sensor interface are routed through a pulse transformer,
which is connected to the pins IBP-IBN. The IBP-IBN pins
must be configured for remote sensor communication
(i.e.,RMT_E=1).
Metrology Temperature Compensation
Since the VREF bandgap amplifier is chopper-stabilized
the DC offset voltage (the most significant long-term
drift mechanism in bandgap voltage references) is
automatically removed by the chopper circuit. Both the
71M654xT and the 71M6x01 feature chopper circuits
for their respective VREF voltage reference. VREF is
trimmed to a target value of 1.195V during the device
manufacturing process and the result of the trim stored in
nonvolatile fuses.
For the 71M654xT device (±0.5% energy accuracy),
the TRIMT[7:0] value can be read by the MPU during
initialization in order to calculate parabolic temperature
compensation coefficients suitable for each individual
71M654xT device. The resulting temperature coefficient
for VREF in the 71M654xT is ±40 ppm/°C.
By using the trim information in the TRIMT register and
the sensed temperature, a gain adjustment for the sensor
can be computed. See the 71M6541DT/FT/GT and
71M6542FT/GT User’s Guide for more information about
compensating sensors for temperature variations.
Connecting I2C EEPROMs
I2C EEPROMs or other I2C compatible devices should
be connected to the DIO pins SEGDIO2 and SEGDIO3.
Pullup resistors of roughly 10kΩ to VV3P3D (to ensure
operation in BRN mode) should be used for both SDCK
and SDATA signals. The DIO_EEX[1:0] field in I/O
RAM must be set to 01 in order to convert the DIO pins
SEGDIO2 and SEGDIO3 to I2C pins SDCK and SDATA.
Connecting Three-Wire EEPROMs
MICROWIRE EEPROMs and other compatible devices
should be connected to the DIO pins SEGDIO2/SDCK
and SEGDIO3/SDATA.
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Figure 12. Typical Current-Sense Circuit Using Current Transformer in a Single-Ended Configuration
Figure 13. Typical Current-Sense Circuit Using Current Transformer in a Differential Configuration
Figure 14. Typical Current-Sense Circuit Using Shunt in a Differential Configuration
Figure 11. Typical Voltage Sense Circuit Using Resistive Divider
R
IN
VIN
VA
V3P3
A
ROUT
VOUT
IOUT
IAP
V3P3
A
CT
1:N
IIN
RBURDEN
NOISE FILTER
IOUT
IAP
IAN
V3P3A
CT
1:N
IIN
VOUT
RBURDEN
BIAS NETWORK AND NOISE FILTER
IIN
IAP
IAN
V3P3A
VOUT
RSHUNT
BIAS NETWORK AND NOISE FILTER
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Figure 15. 71M6541DT/FT/GT Typical Operating Circuit Using Locally Connected Sensors
MPU
RTC
TIMERS
IAP
VA
IBP
XIN
XOUT
RX
TX
TX
RX
COM0...5
V3P3A V3P3SYS
VBAT
VBAT_RTC
SEG
GNDA GNDD
SEG/DIO
DIO
ICE
LINE
NEUTRAL
LOAD
PULSES,
DIO
IR
AMR
POWER FAULT
COMPARATOR
MODULATOR
SERIAL PORTS
OSCILLATOR/PLL
MUX AND ADC
LCD DRIVER
DIO, PULSES
COMPUTE
ENGINE
FLASH MEMORY
RAM
32 kHz
REGULATOR
SHUNT
CT OR
POWER SUPPLY
71M6541DT
71M6541FT
71M6541GT
TEMPERATURE
SENSOR
VREF
BATTERY
RTC
BATTERY
PWR MODE
CONTROL
WAKE-UP
NEUTRAL
I2C OR µWire
EEPROM
IAN
IBN
V3P3D
BATTERY
MONITOR
SPI INTERFACE
HOST
LCD DISPLAY
RESISTOR DIVIDER
LINE
LINE
NOTE: THIS SYSTEM IS REFERENCED TO LINE.
CT OR
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Figure 16. 71M6541DT/FT/GT Typical Operating Circuit Using Remote Neutral Current Sensor
MPU
RTC
TIMERS
IAP
VA
IBP
XIN
XOUT
RX
TX
TX
RX
COM0...5
V3P3A V3P3SYS
VBAT
VBAT_RTC
SEG
GNDA GNDD
SEG/DIO
DIO
ICE
LINE
NEUTRAL
LOAD
PULSES,
DIO
IR
AMR
POWER FAULT
COMPARATOR
MODULATOR
SERIAL PORTS
OSCILLATOR/PLL
MUX AND ADC
LCD DRIVER
DIO, PULSES
COMPUTE
ENGINE
FLASH MEMORY
RAM
32 kHz
REGULATOR
SHUNT
SHUNT
POWER SUPPLY
71M6541DT
71M6541FT
71M6541GT
TEMPERATURE
SENSOR
VREF
BATTERY
RTC
BATTERY
PWR MODE
CONTROL
WAKE-UP
NEUTRAL
I2C OR µWire
EEPROM
IAN
IBN
V3P3D
BATTERY
MONITOR
SPI INTERFACE
HOST
LCD DISPLAY
RESISTOR DIVIDER
PULSE
TRANSFORMER
LINE
LINE
NOTE: THIS SYSTEM IS REFERENCED TO LINE.
71M6xx1
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Figure 17. 71M6542FT/GT Typical Operating Circuit Using Local Sensors
MPU
RTC
TIMERS
IAP
VA
IBP
XIN
XOUT
RX
TX
TX
RX
COM0...5
V3P3A V3P3SYS
VBAT
VBAT_RTC
SEG
GNDA GNDD
SEG/DIO
DIO
ICE
PHASE B
PHASE A
NEUTRAL
LOAD
PULSES,
DIO
IR
AMR
POWER FAULT
COMPARATOR
MODULATOR
SERIAL PORTS
OSCILLATOR/PLL
MUX AND ADC
LCD DRIVER
DIO, PULSES
COMPUTE
ENGINE
FLASH MEMORY
RAM
32 kHz
REGULATOR
SHUNT
CT OR
POWER SUPPLY
71M6542FT
71M6542GT
TEMPERATURE
SENSOR
VREF
BATTERY
RTC
BATTERY
PWR MODE
CONTROL
WAKE-UP
NEUTRAL
I2C OR µWire
EEPROM
IAN
IBN
V3P3D
BATTERY
MONITOR
SPI INTERFACE
HOST
LCD DISPLAY
PHASE A
PHASE A
NOTE: THIS SYSTEM IS REFERENCED TO PHASE A.
VB
LOAD
SHUNT
RESISTOR DIVIDER
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Figure 18. 71M6542FT/GT Typical Operating Circuit Using Remote Neutral Current Sensor
MPU
RTC
TIMERS
IAP
VA
IBP
XIN
XOUT
RX
TX
TX
RX
COM0...5
V3P3A V3P3SYS
VBAT
VBAT_RTC
SEG
GNDA GNDD
SEG/DIO
DIO
ICE
PHASE B
PHASE A
NEUTRAL
LOAD
PULSES,
DIO
IR
AMR
POWER FAULT
COMPARATOR
MODULATOR
SERIAL PORTS
OSCILLATOR/PLL
MUX AND ADC
LCD DRIVER
DIO, PULSES
COMPUTE
ENGINE
FLASH MEMORY
RAM
32 kHz
REGULATOR
SHUNT
POWER SUPPLY
71M6542FT
71M6542GT
TEMPERATURE
SENSOR
VREF
BATTERY
RTC
BATTERY
PWR MODE
CONTROL
WAKE-UP
NEUTRAL
I2C OR µWire
EEPROM
IAN
IBN
V3P3D
BATTERY
MONITOR
SPI INTERFACE
HOST
LCD DISPLAY
PHASE A
PHASE A
NOTE: THIS SYSTEM IS REFERENCED TO PHASE A.
VB
LOAD
SHUNT
RESISTOR DIVIDER
PULSE
TRANSFORMER
71M6xx1
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UART0
The UART0 RX pin should be pulled down by a 10kΩ
resistor and additionally protected by a 100pF ceramic
capacitor.
Optical Interface
TheOPT_TXandOPT_RXpinscanbeusedforaregular
serialinterface(byconnectingaRS_232transceiverfor
example), or they can be used to directly operate optical
components (for example, an infrared diode and pho-
totransistor implementing a FLAG interface). Figure 21
shows the basic connections for UART1.The OPT_TX
pinbecomesactivewhentheI/ORAMcontrolfieldOPT_
TXE (I/O RAM 0x2456[3:2]) is set to 00.
The polarity of the OPT_TX and OPT_RX pins can be
inverted with the configuration bits, OPT_TXINV and
OPT_RXINV,respectively.
TheOPT_TXoutputmaybemodulatedat38kHzwhen
system power is present. Modulation is not available in
BRN mode. The OPT_TXMOD bit enables modulation.
ThedutycycleiscontrolledbyOPT_FDC[1:0],whichcan
select 50%, 25%, 12.5%, and 6.25% duty cycle. A 6.25%
dutycyclemeansOPT_TXislowfor6.25%oftheperiod.
The OPT_RX pin uses digital signal thresholds. It may
need an analog filter when receiving modulated optical
signals.
With modulation, an optical emitter can be operated at
higher current than nominal, enabling it to increase the
distance along the optical path.
If operation in BRN mode is desired, the external
components should be connected to VV3P3D. However, it
is recommended to limit the current to a few mA.
Figure 19. Typical I2C Operating Circuit
Figure 20. Typical UART Operating Circuit
Figure 21. Optical Interface Typical Operating Circuit
10kΩ
V3P3D
SDCK
EEPROM
71M654xT
SEGDIO2/SDCK
10kΩ
SDATASEGDIO3/SDATA
10kΩ
R1
R2
71M654xT
OPT_RX
100pF
V3P3SYS
V3P3SYS
PHOTOTRANSISTOR
LED
OPT_TX
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Figure 22. Typical Reset Circuits
Figure 23. Typical Emulator Connections
Reset
Even though a functional meter does not necessarily
need a reset switch, it is useful to have a reset push-
button for prototyping. The RESET signal may be sourced
from VV3P3SYS (functional in MSN mode only), VV3P3D
(MSN and BRN modes), or VBAT (all modes, if a battery
is present), or from a combination of these sources,
depending on the application.
For a production meter, the RESET pin should be pro-
tected by the external components. R1 should be in the
rangeof100Ωandmountedascloselyaspossibletothe
IC.Emulator Port Pins
Even when the emulator is not used, small shunt capaci-
tors to ground (22pF) should be used for protection from
EMI.ProductionboardsshouldhavetheICE_Epincon-
nected to ground.
MPU Firmware Library
All application-specific MPU functions are featured in the
demonstration C source code supplied by Maxim Integrated.
The code is available as part of the Demonstration Kit for the
71M6541DT/FT/GT and 71M6542FT/GT. The Demonstration
Kits come with pre programmed with demo firmware and
mounted on a functional sample meter Demo Board. The
DemoBoardsallowforquickandefficientevaluationofthe
IC without having to write firmware or having to supply an in-
circuit emulator (ICE). Contact Maxim Integrated for informa-
tion on price and availability of demonstration boards.
R1
10kΩ
R2
1kΩ
71M654xT
V3P3D
VBAT/
V3P3D
RESET
SWITCH
0.1µF
RESET
GNDD
R1
100Ω
RESET
GNDD
62Ω
71M654xT
E_RST
22pF 22pF 22pF
62Ω
E_RXT
62Ω
E_TCLK
ICE_E
V3P3D
LCD SEGMENTS
(OPTIONAL)
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Energy Meter ICs
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Table 12. I/O RAM Locations in Numerical Order
NAME ADDR BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
CE6 2000 EQU[2:0] U CHOP_E[1:0] RTM_E CE_E
CE5 2001 U SUM_SAMPS[12:8]
CE4 2002 SUM_SAMPS[7:0]
CE3 2003 U CE_LCTN[6:0] for 71M6541GT/42GT, CE_LCTN[5:0] for 71M6541DT/41FT/42FT
CE2 2004 PLS_MAXWIDTH[7:0]
CE1 2005 PLS_INTERVAL[7:0]
CE0 2006 R R DIFFB_E DIFFA_E RFLY_DIS FIR_LEN[1:0] PLS_INV
RCE0 2007 CHOPR[1:0] R R RMT_E R R R
RTMUX 2008 U TMUXRB[2:0] U TMUXRA[2:0]
Reserved 2009 U U R U U U U U
MUX5 200A MUX_DIV[3:0] MUX10_SEL
MUX4 200B MUX9_SEL MUX8_SEL
MUX3 200C MUX7_SEL MUX6_SEL
MUX2 200D MUX5_SEL MUX4_SEL
MUX1 200E MUX3_SEL MUX2_SEL
MUX0 200F MUX1_SEL MUX0_SEL
TEMP 2010 TEMP_BSEL TEMP_PWR OSC_COMP TEMP_BAT U TEMP_PER[2:0]
LCD0 2011 LCD_E LCD_MODE[2:0] LCD_ALLCOM LCD_Y LCD_CLK[1:0]
LCD1 2012 LCD_VMODE[1:0] LCD_BLNKMAP23[5:0]
LCD2 2013 LCD_BAT R LCD_BLNKMAP22[5:0]
LCD_MAP6 2014 LCD_MAP[55:48]
LCD_MAP5 2015 LCD_MAP[47:40]
LCD_MAP4 2016 LCD_MAP[39:32]
LCD_MAP3 2017 LCD_MAP[31:24]
LCD_MAP2 2018 LCD_MAP[23:16]
LCD_MAP1 2019 LCD_MAP[15:8]
LCD_MAP0 201A LCD_MAP[7:0]
DIO_R5 201B U U U U U DIO_RPB[2:0]
DIO_R4 201C U DIO_R11[2:0] U DIO_R10[2:0]
DIO_R3 201D U DIO_R9[2:0] U DIO_R8[2:0]
DIO_R2 201E U DIO_R7[2:0] U DIO_R6[2:0]
DIO_R1 201F U DIO_R5[2:0] U DIO_R4[2:0]
DIO_R0 2020 U DIO_R3[2:0] U DIO_R2[2:0]
DIO0 2021 DIO_EEX[1:0] U U OPT_TXE[1:0] OPT_TXMOD OPT_TXINV
DIO1 2022 DIO_PW DIO_PV OPT_FDC[1:0] U OPT_RXDIS OPT_RXINV OPT_BB
DIO2 2023 DIO_PX DIO_PY U U U U U U
INT1_E 2024 EX_EEX EX_XPULSE EX_YPULSE EX_RTCT EX_TCTEMP EX_RTC1M EX_RTC1S EX_XFER
INT2_E 2025 EX_SPI EX_WPULSE EX_VPULSE
WAKE_E 2026 U EW_TEMP U EW_RX EW_PB EW_DIO4 EW_DIO52†EW_DIO55
SFMM 2080 SFMM[7:0] (via SPI slave port only)
SFMS 2081 SFMS[7:0] (via SPI slave port only)
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Table 12. I/O RAM Locations in Numerical Order (continued)
NAME ADDR BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
CE AND ADC
MUX5 2100 MUX_DIV[3:0] MUX10_SEL[3:0]
MUX4 2101 MUX9_SEL[3:0] MUX8_SEL[3:0]
MUX3 2102 MUX7_SEL[3:0] MUX6_SEL[3:0]
MUX2 2103 MUX5_SEL[3:0] MUX4_SEL[3:0]
MUX1 2104 MUX3_SEL[3:0] MUX2_SEL[3:0]
MUX0 2105 MUX1_SEL[3:0] MUX0_SEL[3:0]
CE6 2106 EQU[2:0] U CHOP_E[1:0] RTM_E CE_E
CE5 2107 U U U SUM_SAMPS[12:8]
CE4 2108 SUM_SAMPS[7:0]
CE3 2109 U CE_LCTN[6:0] for 71M6541GT/42GT, CE_LCTN[5:0] for 71M6541DT/41FT/42FT
CE2 210A PLS_MAXWIDTH[7:0]
CE1 210B PLS_INTERVAL[7:0]
CE0 210C R R DIFFB_E DIFFA_E RFLY_DIS FIR_LEN[1:0] PLS_INV CE0
RTM0 210D U U U U U U RTM0[9:8]
RTM0 210E RTM0[7:0]
RTM1 210F RTM1[7:0]
RTM2 2110 RTM2[7:0]
RTM3 2111 RTM3[7:0]
FIR_EXT 2112 U U U U SLOT_EXT[3:0]
CLOCK GENERATION
CKGN 2200 OUT_SQ[1:0] ADC_DIV PLL_FAST RESET MPU_DIV[2:0]
VREF TRIM FUSES
TRIMT 2309 TRIMT[7:0]
LCD/DIO
LCD0 2400 LCD_E LCD_MODE[2:0] LCD_ALLCOM LCD_Y LCD_CLK[1:0]
LCD1 2401 LCD_VMODE[1:0] LCD_BLNKMAP23[5:0]
LCD2 2402 LCD_BAT R LCD_BLNKMAP22[5:0]
LCD_MAP6 2405 LCD_MAP[55:48]
LCD_MAP5 2406 LCD_MAP[47:40]
LCD_MAP4 2407 LCD_MAP[39:32]
LCD_MAP3 2408 LCD_MAP[31:24]
LCD_MAP2 2409 LCD_MAP[23:16]
LCD_MAP1 240A LCD_MAP[15:8]
LCD_MAP0 240B LCD_MAP[7:0]
LCD4 240C U U U U U LCD_RST LCD_BLANK LCD_ON
LCD_DAC 240D U U U LCD_DAC[4:0]
SEGDIO0 2410 U U LCD_SEG0[5:0]
SEGDIO1 2411 U U LCD_SEG1[5:0]
SEGDIO2 2412 U U LCD_SEG2[5:0]
SEGDIO3 2413 U U LCD_SEG3[5:0]
SEGDIO4 2414 U U LCD_SEG4[5:0]
SEGDIO5 2415 U U LCD_SEG5[5:0]
SEGDIO6 2416 U U LCD_SEG6[5:0]
SEGDIO7 2417 U U LCD_SEG7[5:0]
SEGDIO8 2418 U U LCD_SEG8[5:0]
SEGDIO9 2419 U U LCD_SEG9[5:0]
SEGDIO10 241A U U LCD_SEG10[5:0]
SEGDIO11 241B U U LCD_SEG11[5:0]
SEGDIO12 241C U U LCD_SEG12[5:0]
SEGDIO13 241D U U LCD_SEG13[5:0]
SEGDIO14 241E U U LCD_SEG14[5:0]
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Energy Meter ICs
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Table 12. I/O RAM Locations in Numerical Order (continued)
NAME ADDR BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
SEGDIO15 241F U U LCD_SEG15[5:0]
SEGDIO16 2420 U U LCD_SEG16[5:0]
SEGDIO17 2421 U U LCD_SEG17[5:0]
SEGDIO18 2422 U U LCD_SEG18[5:0]
SEGDIO19 2423 U U LCD_SEG19[5:0]
SEGDIO20 2424 U U LCD_SEG20[5:0]
SEGDIO21 2425 U U LCD_SEG21[5:0]
SEGDIO22 2426 U U LCD_SEG22[5:0]
SEGDIO23 2427 U U LCD_SEG23[5:0]
SEGDIO24 2428 U U LCD_SEG24[5:0]
SEGDIO25 2429 U U LCD_SEG25[5:0]
SEGDIO26 242A U U LCD_SEG26[5:0]
SEGDIO27 242B U U LCD_SEG27[5:0]
SEGDIO28 242C U U LCD_SEG28[5:0]
SEGDIO29 242D U U LCD_SEG29[5:0]
SEGDIO30 242E U U LCD_SEG30[5:0]
SEGDIO31 242F U U LCD_SEG31[5:0]
SEGDIO32 2430 U U LCD_SEG32[5:0]
SEGDIO33 2431 U U LCD_SEG33[5:0]
SEGDIO34 2432 U U LCD_SEG34[5:0]
SEGDIO35 2433 U U LCD_SEG35[5:0]
SEGDIO36 2434 U U LCD_SEG36[5:0]
SEGDIO37 2435 U U LCD_SEG37[5:0]
SEGDIO38 2436 U U LCD_SEG38[5:0]
SEGDIO39 2437 U U LCD_SEG39[5:0]
SEGDIO40 2438 U U LCD_SEG40[5:0]
SEGDIO41 2439 U U LCD_SEG41[5:0]
SEGDIO42 243A U U LCD_SEG42[5:0]
SEGDIO43 243B U U LCD_SEG43[5:0]
SEGDIO44 243C U U LCD_SEG44[5:0]
SEGDIO45 243D U U LCD_SEG45[5:0]
SEGDIO46 243E U U LCD_SEG46[5:0]
SEGDIO47 243F U U LCD_SEG47[5:0]
SEGDIO48 2440 U U LCD_SEG48[5:0]
SEGDIO49 2441 U U LCD_SEG49[5:0]
SEGDIO50 2442 U U LCD_SEG50[5:0]
SEGDIO51 2443 U U LCD_SEG51[5:0]
SEGDIO52 2444 U U LCD_SEG52[5:0]
SEGDIO53 2445 U U LCD_SEG53[5:0]
SEGDIO54 2446 U U LCD_SEG54[5:0]
SEGDIO55 2447 U U LCD_SEG55[5:0]
DIO_R5 2450 U U U U U DIO_RPB[2:0]
DIO_R4 2451 U DIO_R11[2:0] U DIO_R10[2:0]
DIO_R3 2452 U DIO_R9[2:0] U DIO_R8[2:0]
DIO_R2 2453 U DIO_R7[2:0] U DIO_R6[2:0]
DIO_R1 2454 U DIO_R5[2:0] U DIO_R4[2:0]
DIO_R0 2455 U DIO_R3[2:0] U DIO_R2[2:0]
DIO0 2456 DIO_EEX[1:0] U UMUX_SEL OPT_TXE[1:0] OPT_TXMOD OPT_TXINV
DIO1 2457 DIO_PW DIO_PV OPT_FDC[1:0] U OPT_RXDIS OPT_RXINV OPT_TXINV
DIO2 2458 DIO_PX DIO_PY U OUT_SQE U U U U
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Energy Meter ICs
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Table 12. I/O RAM Locations in Numerical Order (continued)
NAME ADDR BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
NONVOLATILE BITS
TMUX 2502 U U TMUX[5:0]
TMUX2 2503 U U U TMUX2[4:0]
RTC1 2504 U RTCA_ADJ[6:0]
TC_A1 2508 U U U U U U TC_A[9:8]
TC_A2 2509 TC_A[7:0]
TC_B1 250A U U U U TC_B[11:8]
TC_B2 250B TC_B[7:0]
PQMASK 2511 U U U U U PQMASK[2:0]
TSEL 2518 U U U TEMP_SELE TEMP_SEL[3:0]
TSBASE1 2519 U U U U U SBASE[10:8]
TSBASE2 251A SBASE[7:0]
TSMAX 251B U SMAX[6:0]
TSMIN 251C U SMIN[6:0]
TSFILT 251D U U U U SFILT[3:0]
71M6x01 REMOTE INTERFACE
REMOTE2 2602 RMT_RD[15:8]
REMOTE1 2603 RMT_RD[7:0]
RBITS
INT1_E 2700 EX_EEX EX_XPULSE EX_YPULSE EX_RTCT EX_TCTEMP EX_RTC1M EX_RTC1S EX_XFER
INT2_E 2701 EX_SPI EX_WPULSE EX_VPULSE U U U U U
SECURE 2702 FLSH_UNLOCK[3:0] R FLSH_RDE FLSH_WRE R
Analog0 2704 VREF_CAL VREF_DIS PRE_E ADC_E BCURR SPARE[2:0]
INTBITS 2707 U INT6 INT5 INT4 INT3 INT2 INT1 INT0
FLAG0 SFR E8 IE_EEX IE_XPULSE IE_YPULSE IE_RTCT IE_TCTEMP IE_RTC1M IE_RTC1S IE_XFER
FLAG1 SFR F8 IE_SPI IE_WPULSE IE_VPULSE U U U U PB_STATE
STAT SFR F9 U U U PLL_OK U VSTAT[2:0]
REMOTE0 SFR FC U PERR_RD PERR_WR RCMD[4:0]
SPI1 SFR FD SPI_CMD[7:0]
SPI0 2708 SPI_STAT[7:0]
RCE0 2709 CHOPR[1:0] R R RMT_E R R R
RTMUX 270A U R R R U TMUXRA[2:0]
INFO_PG 270B U U U U U U U INFO_PG
DIO3 270C U U PORT_E SPI_E SPI_SAFE U U U
TNM1 2710 U TEMP_NMAX[14:8]
TNM2 2711 TEMP_NMAX[7:0]
TM1 2712 U U U U TEMP_M[11:8]
TM2 2713 TEMP_M[7:0]
TNB1 2714 TEMP_NBAT[15:8]
TNB2 2715 TEMP_NBAT[7:0]
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Energy Meter ICs
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Table 12. I/O RAM Locations in Numerical Order (continued)
NAME ADDR BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
NV RAM AND RTC
NVRAMxx 2800 NVRAM[0] to NVRAM[7F] - 128 bytes, direct access, 0x2800 to 0x287F
WAKE 2880 WAKE_TMR[7:0]
STEMP1 2881 STEMP[15:8]
STEMP0 2882 STEMP[7:0]
BSENSE 2885 BSENSE[7:0]
PQ2 2886 U U U PQ[20:16]
PQ1 2887 PQ[15:8]
PQ0 2888 PQ[7:0]
RTC0 2890 RTC_WR RTC_RD U RTC_FAIL U U U U
RTC2 2892 RTC_SBSC[7:0]
RTC3 2893 U U RTC_SEC[5:0]
RTC4 2894 U U RTC_MIN[5:0]
RTC5 2895 U U U RTC_HR[4:0]
RTC6 2896 U U U U U RTC_DAY[2:0]
RTC7 2897 U U U RTC_DATE[4:0]
RTC8 2898 U U U U RTC_MO[3:0]
RTC9 2899 RTC_YR[7:0]
RTC11 289C U U U U TC_C[11:8]
RTC12 289D TC_C[7:0]
RTC13 289E U U RTC_TMIN[5:0]
RTC14 289F U U U RTC_THR[4:0]
TEMP 28A0 TEMP_BSEL TEMP_PWR OSC_COMP TEMP_BAT TBYTE_BUSY TEMP_PER[2:0]
WF1 28B0 WF_CSTART WF_RST WF_RSTBIT WF_OVF WF_ERST WF_BADVDD U U
WF2 28B1 U WF_TEMP WF_TMR WF_RX WF_PB WF_DIO4 WF_DIO52 WF_DIO55
MISC 28B2 SLEEP LCD_ONLY WAKE_ARM U U U U U
WAKE_E 28B3 U EW_TEMP U EW_RX EW_PB EW_DIO4 EW_DIO52 † EW_DIO55
WDRST 28B4 WD_RST TEMP_START U U U U U U
MPU PORTS
P3 SFR B0 DIO_DIR[15:12] DIO[15:12]
P2 SFR A0 DIO_DIR[11:8] DIO[11:8]
P1 SFR 90 DIO_DIR[7:4] DIO[7:4]
P0 SFR 80 DIO_DIR[3:0] DIO[3:0]
FLASH
FLSH_ERASE SFR 94 FLSH_ERASE[7:0]
FLSH_CTL SFR B2 PREBOOT SECURE U U FLSH_PEND FLSH_PSTWR FLSH_MEEN FLSH_PWE
FLSH_BANK SFR B6 U U U U U U FLSH_BANK[1:0]
FLSH_PGADR SFR B7 FLSH_PGADR[6:0] U
I2C
EEDATA SFR 9E EEDATA[7:0]
EECTRL SFR 9F EECTRL[7:0]
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Table 13. I/O RAM Locations in Alphabetical Order
NAME LOCATION RST WK DIR DESCRIPTION
ADC_E 2704[4] 0 0 R/W Enables ADC and VREF. When disabled, reduces bias current.
ADC_DIV 2200[5] 0 0 R/W
ADC_DIVcontrolstherateoftheADCandFIRclocks.
TheADC_DIVsettingdetermineswhetherMCKisdividedby4or8:
0=MCK/4
1=MCK/8
The resulting ADC and FIR clock is as shown below.
PLL_FAST = 0 PLL_FAST = 1
MCK 6.291456MHz 19.660800MHz
ADC_DIV=0 1.572864MHz 4.9152MHz
ADC_DIV=1 0.786432MHz 2.4576MHz
BCURR 2704[3] 0 0 R/W Connectsa100µAloadtothebatteryselectedbyTEMP_BSEL.
BSENSE[7:0] 2885[7:0] – – R The result of the battery measurement.
CE_E 2106[0] 0 0 R/W CE enable.
CE_LCTN[6:0]
CE_LCTN[5:0]
2109[6:0]
2109[5:0] 31 31 R/W
CEprogramlocation.ThestartingaddressfortheCEprogramis1024xCE_LCTN.
CE_LCTN[6:0],2109[6:0]for71M6541GT/42GT
CE_LCTN[5:0],2109[5:0]for71M6541DT/41FT/42FT
CHIP_ID[15:0] 2300[7:0]
2301[7:0]
0
0
0
0
R
R
Thesebytescontainthechipidentication.
CHIP[15:0]:
71M6541DT (118Ch)
71M6541FT (1194h)
71M6542FT (0808h)
71M6541GT (2009h)
71M6542GT (2011h)
CHOP_E[1:0] 2106[3:2] 0 0 R/W
Chop enable for the reference bandgap circuit. The value of CHOP changes on the rising edge of MUXSYNC
accordingtothevalueinCHOP_E:
00=toggle101=positive10=reversed11=toggle
1except at the mux sync edge at the end of an accumulation interval.
Note:CHOP_E=11isthepreferredmodeforlow-noiseapplications.
CHOPR[1:0] 2709[7:6] 00 00 R/W
The CHOP settings for the remote sensor.
00=Autochop.ChangeeveryMUXframe.
01=Positive
10=Negative
11=Autochop.Sameas00.
DIFFA_E 210C[4] 0 0 R/W EnablesdifferentialcongurationfortheIAcurrentinput(IAP-IAN).
DIFFB_E 210C[5] 0 0 R/W EnablesdifferentialcongurationfortheIBcurrentinput(IBP-IBN).
DIO_R2[2:0]
DIO_R3[2:0]
DIO_R4[2:0]
DIO_R5[2:0]
DIO_R6[2:0]
DIO_R7[2:0]
DIO_R8[2:0]
DIO_R9[2:0]
DIO_R10[2:0]
DIO_R11[2:0]
DIO_RPB[2:0]
2455[2:0]
2455[6:4]
2454[2:0]
2454[6:4]
2453[2:0]
2453[6:4]
2452[2:0]
2452[6:4]
2451[2:0]
2451[6:4]
2450[2:0]
0
0
0
0
0
0
0
0
0
0
0
- R/W
Connects PB and dedicated I/O pins DIO2 through DIO11 to internal resources. If more than one input is
connectedtothesameresource,theMULTIPLEcolumnbelowspecieshowtheyarecombined.
DIO_Rx RESOURCE MULTIPLE
0 NONE –
1 Reserved OR
2 T0 (Timer0 clock or gate) OR
3 T1 (Timer1 clock or gate) OR
4 IO interrupt (int0) OR
5 IO interrupt (int1) OR
DIO_DIR[15:12]
DIO_DIR[11:8]
DIO_DIR[7:4]
DIO_DIR[3:0]
SFR B0[7:4]
SFR A0[7:4]
SFR 90[7:4]
SFR 80[7:4]
F F R/W
Programsthedirectionoftherst16DIOpins.1indicatesoutput.Ignoredifthepinisnotconguredas
I/O.SeeDIO_PVandDIO_PWforspecialoptionfortheSEGDIO0andSEGDIO1outputs.SeeDIO_EEX
for special option for SEGDIO2 and SEGDIO3. Note that the direction of DIO pins above 15 is set by
SEGDIOx[1].SeePORT_Etoavoidpower-upspikes.
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Table 13. I/O RAM Locations in Alphabetical Order (continued)
NAME LOCATION RST WK DIR DESCRIPTION
DIO[15:12]
DIO[11:8]
DIO[7:4]
DIO[3:0]
SFR B0[3:0]
SFR A0[3:0]
SFR 90[3:0]
SFR 80[3:0]
F F R/W
Thevalueontherst16DIOpins.PinsconguredasLCDreadszero.Whenwritten,changesdataonpins
conguredasoutputs.PinsconguredasLCDorinputignorewrites.NotethatthedataforDIOpinsabove
15 is set by SEGDIOx[0].
DIO_EEX[1:0] 2456[7:6] 0 - R/W
When set, converts pins SEGDIO3/SEGDIO2 to interface with external EEPROM. SEGDIO2 becomes SDCK
andSEGDIO3becomesbidirectionalSDATA,butonlyifLCD_MAP[2]andLCD_MAP[3]arecleared.
DIO_EEX[1:0] FUNCTION
00 Disable EEPROM interface
01 2-Wire EEPROM interface
10 3-Wire EEPROM interface
11 3-Wire EEPROM interface with separate DO (DIO3) and DI (DIO8) pins.
DIO_PV 2457[6] 0 – R/W CausesVARPULSEtobeoutputonpinSEGDIO1,ifLCD_MAP[1]=0.
DIO_PW 2457[7] 0 – R/W CausesWPULSEtobeoutputonpinSEGDIO0,ifLCD_MAP[0]=0.
DIO_PX 2458[7] 0 – R/W CausesXPULSEtobeoutputonpinSEGDIO6,ifLCD_MAP[6]=0.
DIO_PY 2458[6] 0 – R/W CausesYPULSEtobeoutputonpinSEGDIO7,ifLCD_MAP[7]=0.
EEDATA[7:0] SFR 9E 0 0 R/W Serial EEPROM interface data.
EECTRL[7:0] SFR 9F 0 0 R/W
Serial EEPROM interface control.
STATUS
BIT NAME READ/
WRITE
RESET
STATE POLARITY DESCRIPTION
7 ERROR R 0 Positive 1 when an illegal
command is received.
6 BUSY R 0 Positive 1 when serial data bus
is busy.
5RX_ACK R 1 Positive
1 indicates that the
EEPROM sent an ACK
bit.
EQU[2:0] 2106[7:5] 0 0 R/W
Speciesthepowerequation.
EQU Watt & VAR Formula
(WSUM/VARSUM)
Inputs Used for Energy/Current Calculation
W0SUM/
VAR0SUM
W1SUM/
VAR1SUM
I0SQ
SUM
I1SQ
SUM
0VA x IA
1 element, 2W 1fVA x IA VA x IB1 IA IB1
1VA x (IA-IB)/2
1 element, 3W 1fVA x (IA-IB)/2 – IA-IB IB
2† VA x IA + VB x IB
2 element, 3W 3f Delta VA x IA VB x IB IA IB
Note: Optionally, IB may be used to measure neutral current.
† 71M6542FT/GT only
EX_XFER
EX_RTC1S
EX_RTC1M
EX_TCTEMP
EX_RTCT
EX_SPI
EX_EEX
EX_XPULSE
EX_YPULSE
EX_WPULSE
EX_VPULSE
2700[0]
2700[1]
2700[2]
2700[3]
2700[4]
2701[7]
2700[7]
2700[6]
2700[5]
2701[6]
2701[5]
0 0 R/W
Interruptenablebits.ThesebitsenabletheXFER_BUSY,theRTC_1SEC,etc.Thebitsaresetbyhardware
and cannot be set by writing a 1. The bits are reset by writing 0. Note that if one of these interrupts is to
enabled, its corresponding 8051 EX enable bit must also be set.
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Table 13. I/O RAM Locations in Alphabetical Order (continued)
NAME LOCATION RST WK DIR DESCRIPTION
EW_DIO4 28B3[2] 0 – R/W Connects SEGDIO4 to the WAKE logic and permits SEGDIO4 rising to wake the part. This bit has no effect
unlessDIO4isconguredasadigitalinput.
EW_DIO52 28B3[1] 0 – R/W
Connects SEGDIO52 to the WAKE logic and permits SEGDIO52 rising to wake the part. This bit has no
effectunlessSEGDIO52isconguredasadigitalinput.
The SEGDIO52 pin is only available in the 71M6542FT.
EW_DIO55 28B3[0] 0 – R/W Connects SEGDIO55 to the WAKE logic and permits SEGDIO55 rising to wake the part. This bit has no
effectunlessSEGDIO55isconguredasadigitalinput.
EW_PB 28B3[3] 0 – R/W ConnectsPBtotheWAKElogicandpermitsPBrisingtowakethepart.PBisalwaysconguredasaninput.
EW_RX 28B3[4] 0 – R/W Connects RX to the WAKE logic and permits RX rising to wake the part. See the WAKE description on page
84 for de-bounce issues.
EW_TEMP 28B3[5] 0 – R/W Connects the temperature range check hardware to the WAKE logic and permits the range check hardware
to wake the part.
FIR_LEN[1:0] 210C[2:1] 0 0 R/W
DeterminesthenumberofADCcyclesintheADCdecimationFIRlter.
PLL_FAST=1:
FIR_LEN[1:0] ADC Cycles
00 141
01 288
10 384
PLL_FAST=0:
FIR_LEN[1:0] ADC Cycles
00 135
01 276
10 Not Allowed
TheADCLSBsizeandfull-scalevaluesdependontheFIR_LEN[1:0]setting.
FLSH_BANK[7:0] SFR B6[1:0] 01 01 R/W
Flash Bank Selection
FLSH_BANK[1:0] ADDRESS RANGE FOR LOWER
BANK (0x0000–0x7FFF)
ADDRESS RANGE FOR UPPER BANK
(0x8000–0x7FFF)
00 0x0000–0x7FFF 0x0000–0x7FFF
01 0x0000–0x7FFF 0x8000–0x7FFF
10 0x0000–0x7FFF 0x10000–0x17FFFF
11 0x0000–0x7FFF 0x18000–0x1FFFF
FLSH_ERASE[7:0] SFR 94[7:0] 0 0 W
Flash Erase Initiate
FLSH_ERASEisusedtoinitiateeithertheFlashMassErasecycleortheFlashPageErasecycle.Specic
patternsareexpectedforFLSH_ERASEinordertoinitiatetheappropriateErasecycle.
(default=0x00).
0x55=InitiateFlashPageErasecycle.MustbeproceededbyawritetoFLSH_PGADR[6:0](SFR
0xB7[7:1]).
0xAA=InitiateFlashMassErasecycle.MustbeproceededbyawritetoFLSH_MEENandtheICEportmust
be enabled.
AnyotherpatternwrittentoFLSH_ERASEhasnoeffect.
FLSH_MEEN SFR B2[1] 0 0 W
Mass Erase Enable
0=MassErasedisabled(default).
1=MassEraseenabled.
Must be re-written for each new Mass Erase cycle.
FLSH_PEND SFR B2[3] 0 0 R Indicatesthatatimedashwriteispending.Ifanotherashwriteisattempted,itisignored.
FLSH_PGADR[6:0] SFR B7[7:1] 0 0 W
Flash Page Erase Address
FlashPageAddress(page0thru63)thatiserasedduringthePageErasecycle.(default=0x00).
Must be re-written for each new Page Erase cycle.
FLSH_PSTWR SFR B2[2] 0 0 R/W
Enablestimedashwrites.When1,andifCE_E=1,ashwriterequestsarestoredinaone-elementdeep
FIFOandareexecutedwhenCE_BUSYfalls.FLSH_PENDcanbereadtodeterminethestatusoftheFIFO.
IfFLSH_PSTWR=0orifCE_E=0,ashwritesareimmediate.
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Table 13. I/O RAM Locations in Alphabetical Order (continued)
NAME LOCATION RST WK DIR DESCRIPTION
FLSH_PWE SFR B2[0] 0 0 R/W
Program Write Enable
0=MOVXcommandsrefertoExternalRAMSpace,normaloperation(default).
1=MOVX@DPTR,AmovesAtoExternalProgramSpace(Flash)@DPTR.
Thisbitisautomaticallyresetaftereachbytewrittentoash.Writestothisbitareinhibitedwheninterrupts
are enabled.
FLSH_RDE 2702[2] – – R IndicatesthattheashmaybereadbyICEorSPIslave.FLSH_RDE=(!SECURE)
FLSH_UNLOCK[3:0] 2702[7:4] 0 0 R/W Mustbea‘2’toenableanyashmodication.SeethedescriptionofFlashsecurityformoredetails.
FLSH_WRE 2702[1] – – R IndicatesthattheashmaybewrittenthroughICEorSPIslaveports.
IE_XFER
IE_RTC1S
IE_RTC1M
IE_TCTEMP
IE_RTCT
IE_SPI
IE_EEX
IE_XPULSE
IE_YPULSE
IE_WPULSE
IE_VPULSE
SFR E8[0]
SFR E8[1]
SFR E8[2]
SFR E8[3]
SFR E8[4]
SFR F8[7]
SFR E8[7]
SFR E8[6]
SFR E8[5]
SFR F8[4]
SFR F8[3]
0 0 R/W
Interruptagsforexternalinterrupts2,5,and6.Theseagsmonitorthesourceoftheint2,int5,andint6
interrupts(externalinterruptstotheMPUcore).Theseagsaresetbyhardwareandmustbeclearedbythe
softwareinterrupthandler.TheIEX2(SFR0xC0[1])andIEX6(SFR0xC0[5])interruptagsareautomatically
cleared by the MPU core when it vectors to the interrupt handler. IEX2 and IEX6 must be cleared by writing
zero to their corresponding bit positions in SFR 0xC0, while writing ones to the other bit positions that are not
being cleared.
INTBITS 2707[6:0] – – R Interrupt inputs. The MPU may read these bits to see the input to external interrupts INT0, INT1, up to INT6.
These bits do not have any memory and are primarily intended for debug use.
LCD_ALLCOM 2400[3] 0 – R/W ConguresSEG/COMbitsasCOM.HasnoeffectonpinswhoseLCD_MAPbitiszero.
LCD_BAT 2402[7] 0 – R/W Connects the LCD power supply to VBAT in all modes.
LCD_BLNKMAP23[5:0]
LCD_BLNKMAP22[5:0]
2401[5:0]
2402[5:0] 0 – R/W IdentieswhichsegmentsconnectedtoSEG23andSEG22shouldblink.1means‘blink.’Themost
signicantbitcorrespondstoCOM5,theleastsignicant,toCOM0.
LCD_CLK[1:0] 2400[1:0] 0 – R/W
SetstheLCDclockfrequency.Note:fw=32,768Hz
LCD_CLK LCD Clock Frequency
00 64 Hz
01 128 Hz
10 256 Hz
11 512 Hz
LCD_DAC[4:0] 240D[4:0] 0 – R/W
The LCD contrast DAC. This DAC controls the VLCD voltage and has an output range of 2.5V to 5V. The
VLCD voltage is
VLCD=2.5+2.5xLCD_DAC[4:0]/31
Thus, the LSB of the DAC is 80.6mV. The maximum DAC output voltage is limited by VV3P3SYS, VBAT, and
whetherLCD_BSTE=1.
LCD_E 2400[7] 0 – R/W Enables the LCD display. When disabled, VLC2, VLC1, and VLC0 are ground as are the COM and SEG
outputsiftheirLCD_MAPbitis1.
LCD_MAP[55:48]
LCD_MAP[47:40]
LCD_MAP[39:32]
LCD_MAP[31:24]
LCD_MAP[23:16]
LCD_MAP[15:8]
LCD_MAP[7:0]
2405[7:0]
2406[7:0]
2407[7:0]
2408[7:0]
2409[7:0]
240A[7:0]
240B[7:0]
0
0
0
0
0
0
0
–
–
–
–
–
–
–
R/W
R/W
R/W
R/W
R/W
R/W
R/W
EnablesLCDsegmentdrivermodeofcombinedSEGDIOpins.Pinsthatcannotbeconguredasoutputs
(SEG48throughSEG50)becomeinputswithinternalpullupswhentheirLCD_MAPbitiszero.Also,note
thatSEG48throughSEG50aremultiplexedwiththein-circuitemulatorsignals.WhentheICE_Epinis
high,theICEinterfaceisenabled,andSEG48throughSEG50becomeE_RXTX,E_TCLKandE_RST,
respectively.
LCD_MODE[2:0] 2400[6:4] 0 – R/W
Selects the LCD bias and multiplex mode.
LCD_MODE Output
000 4states,⅓bias
001 3states,⅓bias
010 2 states, ½ bias
011 3 states, ½ bias
100 Static display
101 5states,⅓bias
110 6states,⅓bias
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Table 13. I/O RAM Locations in Alphabetical Order (continued)
NAME LOCATION RST WK DIR DESCRIPTION
LCD_ON
LCD_BLANK
240C[0]
240C[1]
0
0
–
–
R/W
R/W
Turns on or off all LCD segments without changing LCD data. If both bits are set, the LCD display is
turned on.
LCD_ONLY 28B2[6] 0 0 W Puts the IC to sleep, but with LCD display still active. Ignored if system power is present. It awakens when
Wake Timer times out, when certain DIO pins are raised, or when system power returns.
LCD_RST 240C[2] 0 – R/W ClearallbitsofLCDdata.ThesebitsaffectSEGDIOpinsthatareconguredasLCDdrivers.Thisbitdoes
not auto clear.
LCD_SEG0[5:0] 2410[5:0] 0 – R/W SEG Data for SEG0
LCD_SEG1[5:0] 2411[5:0] 0 – R/W SEG Data for SEG1
LCD_SEG2[5:0] 2412[5:0] 0 – R/W SEG Data for SEG2
LCD_SEG3[5:0] 2413[5:0] 0 – R/W SEG Data for SEG3
LCD_SEG4[5:0] 2414[5:0] 0 – R/W SEG Data for SEG4
LCD_SEG5[5:0] 2415[5:0] 0 – R/W SEG Data for SEG5
LCD_SEG6[5:0] 2416[5:0] 0 – R/W SEG Data for SEG6
LCD_SEG7[5:0] 2417[5:0] 0 – R/W SEG Data for SEG7
LCD_SEG8[5:0] 2418[5:0] 0 – R/W SEG Data for SEG8
LCD_SEG9[5:0] 2419[5:0] 0 – R/W SEG Data for SEG9
LCD_SEG10[5:0] 241A[5:0] 0 – R/W SEG Data for SEG10
LCD_SEG11[5:0] 241B[5:0] 0 – R/W SEG Data for SEG11
LCD_SEG12[5:0] 241C[5:0] 0 – R/W SEG Data for SEG12
LCD_SEG13[5:0] 241D[5:0] 0 – R/W SEG Data for SEG13
LCD_SEG14[5:0] 241E[5:0] 0 – R/W SEG Data for SEG14
LCD_SEG15[5:0] 241F[5:0] 0 – R/W SEG Data for SEG15
LCD_SEG16[5:0] 2420[5:0] 0 – R/W SEG Data for SEG16
LCD_SEG17[5:0] 2421[5:0] 0 – R/W SEG Data for SEG17
LCD_SEG18[5:0] 2422[5:0] 0 – R/W SEG Data for SEG18
LCD_SEG19[5:0] 2423[5:0] 0 – R/W SEG Data for SEG19
LCD_SEG20[5:0] 2424[5:0] 0 – R/W SEG Data for SEG20
LCD_SEG21[5:0] 2425[5:0] 0 – R/W SEG Data for SEG21
LCD_SEG22[5:0] 2426[5:0] 0 – R/W SEG Data for SEG22
LCD_SEG23[5:0] 2427[5:0] 0 – R/W SEG Data for SEG23
LCD_SEG24[5:0] 2428[5:0] 0 – R/W SEG Data for SEG24
LCD_SEG25[5:0] 2429[5:0] 0 – R/W SEG Data for SEG25
LCD_SEG26[5:0] 242A[5:0] 0 – R/W SEG Data for SEG26
LCD_SEG27[5:0] 242B[5:0] 0 – R/W SEG Data for SEG27
LCD_SEG28[5:0] 242C[5:0] 0 – R/W SEG Data for SEG28
LCD_SEG29[5:0] 242D[5:0] 0 – R/W SEG Data for SEG29
LCD_SEG30[5:0] 242E[5:0] 0 – R/W SEG Data for SEG30
LCD_SEG31[5:0] 242F[5:0] 0 – R/W SEG Data for SEG31
LCD_SEG32[5:0] 2430[5:0] 0 – R/W SEG Data for SEG32
LCD_SEG33[5:0] 2431[5:0] 0 – R/W SEG Data for SEG33
LCD_SEG34[5:0] 2432[5:0] 0 – R/W SEG Data for SEG34
LCD_SEG35[5:0] 2433[5:0] 0 – R/W SEG Data for SEG35
LCD_SEG36[5:0] 2434[5:0] 0 – R/W SEG Data for SEG36
LCD_SEG37[5:0] 2435[5:0] 0 – R/W SEG Data for SEG37
LCD_SEG38[5:0] 2436[5:0] 0 – R/W SEG Data for SEG38
LCD_SEG39[5:0] 2437[5:0] 0 – R/W SEG Data for SEG39
LCD_SEG40[5:0] 2438[5:0] 0 – R/W SEG Data for SEG40
LCD_SEG41[5:0] 2439[5:0] 0 – R/W SEG Data for SEG41
LCD_SEG42[5:0] 243A[5:0] 0 – R/W SEG Data for SEG42
LCD_SEG43[5:0] 243B[5:0] 0 – R/W SEG Data for SEG43
LCD_SEG44[5:0] 243C[5:0] 0 – R/W SEG Data for SEG44
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Table 13. I/O RAM Locations in Alphabetical Order (continued)
NAME LOCATION RST WK DIR DESCRIPTION
LCD_SEG45[5:0] 243D[5:0] 0 – R/W SEG Data for SEG45
LCD_SEG46[5:0] 243E[5:0] 0 – R/W SEG Data for SEG46
LCD_SEG47[5:0] 243F[5:0] 0 – R/W SEG Data for SEG47
LCD_SEG48[5:0] 2440[5:0] 0 – R/W SEG Data for SEG48
LCD_SEG49[5:0] 2441[5:0] 0 – R/W SEG Data for SEG49
LCD_SEG50[5:0] 2442[5:0] 0 – R/W SEG Data for SEG50
LCD_SEG51[5:0] 2443[5:0] 0 – R/W SEG Data for SEG51
LCD_SEG52[5:0] 2444[5:0] 0 – R/W SEG Data for SEG52
LCD_SEG53[5:0] 2445[5:0] 0 – R/W SEG Data for SEG53
LCD_SEG54[5:0] 2446[5:0] 0 – R/W SEG Data for SEG54
LCD_SEG55[5:0] 2447[5:0] 0 – R/W SEG Data for SEG55
LCD_VMODE[1:0] 2401[7:6] 00 00 R/W
SpecieshowVLCD is generated.
LCD_VMODE Description
11 External VLCD
10 LCD DAC enabled
01 LCD DAC enabled
00 No DAC. VLCD=V3P3L.
LCD_Y 2400[2] 0 – R/W LCDBlinkFrequency(ignoredifblinkisdisabled).
1=1Hz,0=0.5Hz
MPU_DIV[2:0] 2200[2:0] 0 0 R/W
MPU clock rate is:
MPURate=MCKRatex2-(2+MPU_DIV[2:0]).
ThemaximumvalueforMPU_DIV[2:0]is4.BasedonthedefaultvaluesofthePLL_FASTbitandMPU_
DIV[2:0],thepowerupMPUrateis6.29MHz/4=1.5725MHz.TheminimumMPUclockrateis38.4kHzwhen
PLL_FAST=1.
MUX2_SEL[3:0] 2104[3:0] 0 0 R/W Selects which ADC input is to be converted during time slot 2.
MUX3_SEL[3:0] 2104[7:4] 0 0 R/W Selects which ADC input is to be converted during time slot 3.
MUX4_SEL[3:0] 2103[3:0] 0 0 R/W Selects which ADC input is to be converted during time slot 4.
MUX5_SEL[3:0] 2103[7:4] 0 0 R/W Selects which ADC input is to be converted during time slot 5.
MUX6_SEL[3:0] 2102[3:0] 0 0 R/W Selects which ADC input is to be converted during time slot 6.
MUX7_SEL[3:0] 2102[7:4] 0 0 R/W Selects which ADC input is to be converted during time slot 7.
MUX8_SEL[3:0] 2101[3:0] 0 0 R/W Selects which ADC input is to be converted during time slot 8.
MUX9_SEL[3:0] 2101[7:4] 0 0 R/W Selects which ADC input is to be converted during time slot 9.
MUX10_SEL[3:0] 2100[3:0] 0 0 R/W Selects which ADC input is to be converted during time slot 10.
MUX_DIV[3:0] 2100[7:4] 0 0 R/W MUX_DIV[3:0]isthenumberofADCtimeslotsineachMUXframe.Themaximumnumberoftime
slots is 11.
OPT_BB 2457[0] 0 – R/W CongurestheinputoftheopticalporttobeaDIOpintoallowittobebit-banged.Inthiscase,DIO5
becomes a third high speed UART.
OPT_FDC[1:0] 2457[5:4] 0 – R/W
SelectsOPT_TXmodulationdutycycle.
OPT_FDC Function
00 50% Low
01 25% Low
10 12.5% Low
11 6.25% Low
OPT_RXDIS 2457[2] 0 – R/W
OPT_RXcanbeconguredasaninputtotheopticalUARTorasSEGDIO55.
OPT_RXDIS=0andLCD_MAP[55]=0:OPT_RX
OPT_RXDIS=1andLCD_MAP[55]=0:DIO55
OPT_RXDIS=0andLCD_MAP[55]=1:SEG55
OPT_RXDIS=1andLCD_MAP[55]=1:SEG55
OPT_RXINV 2457[1] 0 – R/W InvertsresultfromOPT_RXcomparatorwhen1.AffectsonlytheUARTinput.HasnoeffectwhenOPT_RXis
used as a DIO input.
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Table 13. I/O RAM Locations in Alphabetical Order (continued)
NAME LOCATION RST WK DIR DESCRIPTION
OPT_TXE[1:0] 2456[3:2] 00 – R/W
CongurestheOPT_TXoutputpin.
IfLCD_MAP[51]=0:
00=DIO51,01=OPT_TX,10=WPULSE,11=VARPULSE
IfLCD_MAP[51]=1:
xx=SEG51
OPT_TXINV 2456[0] 0 – R/W InvertOPT_TXwhen1.Thisinversionoccursbeforemodulation.
OPT_TXMOD 2456[1] 0 – R/W EnablesmodulationofOPT_TX.WhenOPT_TXMODisset,OPT_TXismodulatedwhenitwouldotherwise
havebeenzero.ThemodulationisappliedafteranyinversioncausedbyOPT_TXINV.
OSC_COMP 28A0[5] 0 – R/W Enables the automatic update of the PQ RTC compensation value every time the temperature is measured.
OUT_SQ[1:0] 2200[7:6] 0 0 R/W
DenesthesquarewaveoutputonSEGDIO15(ifOUT_SQE=1)
00 – Off
01 – 3.2768MHz
10 – 4.9152MHz
11 – 9.83MHz
OUT_SQE 2458[4] 0 0 R/W EnablesthesquarewaveoutputonSEGDIO15.
PB_STATE SFR F8[0] 0 0 R The de-bounced state of the PB pin.
PERR_RD
PERR_WR
SFR FC[6]
SFR FC[5] 0 0 R/W The IC sets these bits to indicate that a parity error on the remote sensor has been detected. Once set, the
bits are remembered until they are cleared by the MPU.
PLL_OK SFR F9[4] 0 0 R Indicates that the clock generation PLL is settled.
PLL_FAST 2200[4] 0 0 R/W
Controls the speed of the PLL and MCK.
1=19.66MHz(XTALx600)
0=6.29MHz(XTALx192)
PLS_MAXWIDTH[7:0] 210A[7:0] FF FF R/W
PLS_MAXWIDTH[7:0]determinesthemaximumwidthofthepulse(low-goingpulseifPLS_INV=0orhigh-
goingpulseifPLS_INV=1).Themaximumpulsewidthis(2xPLS_MAXWIDTH[7:0]+1)xTI.WhereTIis
PLS_INTERVAL[7:0]inunitsofCK_FIRclockcycles.IfPLS_INTERVAL[7:0]=0orPLS_MAXWIDTH[7:0]=
255, no pulse width checking is performed and the output pulses have 50% duty cycle.
PLS_INTERVAL[7:0] 210B[7:0] 0 0 R/W
PLS_INTERVAL[7:0]determinestheintervaltimebetweenpulses.ThetimebetweenoutputpulsesisPLS_
INTERVAL[7:0]x4inunitsofCK_FIRclockcycles.IfPLS_INTERVAL[7:0]=0,theFIFOisnotusedand
pulsesareoutputassoonastheCEissuesthem.PLS_INTERVAL[7:0]iscalculatedasfollows:
PLS_INTERVAL[7:0]=Floor(MuxframedurationinCK_FIRcycles/
CE pulse updates per Mux frame/4 )
For example, since the 71M654xT CE code is written to generate 6 pulses in one integration interval, when the
FIFOisenabled(i.e.,PLS_INTERVAL[7:0]≠0)andthattheframedurationis1950CK_FIRclockcycles,PLS_
INTERVAL[7:0]shouldbewrittenwithFloor(1950/6/4)=81sothatthevepulsesareevenlyspacedintimeover
the integration interval and the last pulse is issued just prior to the end of the interval.
PLS_INV 210C[0] 0 0 R/W Inverts the polarity of WPULSE, VARPULSE, XPULSE and YPULSE. Normally, these pulses are active low.
When inverted, they become active high.
PORT_E 270C[5] 0 0 R/W EnablesoutputsfromthepinsSEGDIO0-SEGDIO15.PORT_E=0afterresetandpower-upblocksthe
momentary output pulse that would occur on SEGDIO0 to SEGDIO15.
PQ[20:0]
2886[4:0]
2887[7:0]
2888[7:0]
0 0 R Temperaturecompensationvaluecomputedbythequadraticcompensationformula.
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Table 13. I/O RAM Locations in Alphabetical Order (continued)
NAME LOCATION RST WK DIR DESCRIPTION
PQMASK 2511[2:0] 0 0 R/W
Sets the length of the PQ mask. The mask is ANDed with the last four bits of PQ according to the table
below.PQMASKalsodeterminesthelengthofPULSE_AUTOinTMUX.
PQMASK Mask PULSE_AUTO width
000 0000 1s
001 1000 2s
010 1100 4s
011 1110 8s
100 1111 16s
PRE_E 2704[5] 0 0 R/W Enablesthe8xpreamplier.
PREBOOT SFRB2[7] – – R Indicatesthatprebootsequenceisactive.
RCMD[4:0] SFR FC[4:0] 0 0 R/W When the MPU writes a non-zero value to RCMD[4:0], the IC issues a command to the appropriate remote
sensor. When the command is complete, the IC clears RCMD[4:0].
RESET 2200[3] 0 0 W Whenset,writesaonetoWF_RSTBITandthencausesareset.
RFLY_DIS 210C[3] 0 0 R/W Controls how the IC drives the power pulse for the 71M6x01. When set, the power pulse is driven high and
low.Whencleared,itisdrivenhighfollowedbyanopencircuity-backinterval.
RMT_E 2709[3] 0 0 R/W Enables the remote digital isolation interface, which transforms the IBP-IBN pins into a digital balanced
differential pair. Thus, enabling these pins to interface to the 71M6x01 isolated sensor.
RMT_RD[15:8]
RMT_RD[7:0]
2602[7:0]
2603[7:0] 0 0 R Responsefromremotereadrequest.
RTC_FAIL 2890[4] 0 0 R/W Indicates that a count error has occurred in the RTC and that the time is not trustworthy. This bit can be
cleared by writing a 0.
RTC_RD 2890[6] 0 0 R/W FreezestheRTCshadowregistersoitissuitableforMPUreads.WhenRTC_RDisread,itreturnsthestatus
oftheshadowregister:0=uptodate,1=frozen.
RTC_SBSC[7:0] 2892[7:0] – – R Timeremaininguntilthenext1secondboundary.LSB=1/256second.
RTC_TMIN[5:0] 289E[5:0] 0 – R/W Thetargetminutesregister.SeeRTC_THRbelow.
RTC_THR[4:0] 289F[4:0] 0 – R/W Thetargethoursregister.TheRTC_TinterruptoccurswhenRTC_MINbecomesequaltoRTC_TMINand
RTC_HRbecomesequaltoRTC_THR.
RTC_WR 2890[7] 0 0 R/W
FreezestheRTCshadowregistersoitissuitableforMPUwrites.WhenRTC_WRiscleared,the
contents of the shadow register are written to the RTC counter on the next RTC clock (~500 Hz).
WhenRTC_WRisread,itreturns1aslongasRTC_WRisset.ItcontinuestoreturnoneuntiltheRTC
counter actually updates.
RTC_SEC[5:0]
RTC_MIN[5:0]
RTC_HR[4:0]
RTC_DAY[2:0]
RTC_DATE[4:0]
RTC_MO[3:0]
RTC_YR[7:0]
2893[5:0]
2894[5:0]
2895[4:0]
2896[2:0]
2897[4:0]
2898[3:0]
2899[7:0]
–
–
–
–
–
–
–
–
–
–
–
–
–
–
R/W
The RTC interface registers. These are the year, month, day, hour, minute and second parameters for the
RTC.TheRTCissetbywritingtotheseregisters.Year00andallothersdivisibleby4aredenedasaleap
year.
SEC 00 to 59
MIN 00 to 59
HR 00to23 (00=Midnight)
DAY 01to07 (01=Sunday)
DATE 01 to 31
MO 01 to 12
YR 00 to 99
Each write operation to one of these registers must be preceded by a write to 0x20A0.
RTCA_ADJ[6:0] 2504[7:0] 40 – R/W AnalogRTCfrequencyadjustregister.
RTM_E 2106[1] 0 0 R/W Real Time Monitor enable. When 0, the RTM output is low.
RTM0[9:8]
RTM0[7:0]
RTM1[7:0]
RTM2[7:0]
RTM3[7:0]
210D[1:0]
210E[7:0]
210F[7:0]
2110[7:0]
2111[7:0]
0
0
0
0
0
0
0
0
0
0
R/W
Four RTM probes. Before each CE code pass, the values of these registers are serially output on the RTM
pin.TheRTMregistersareignoredwhenRTM_E=0.NotethatRTM0is10bitswide.Theothersassume
the upper two bits are 00.
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Table 13. I/O RAM Locations in Alphabetical Order (continued)
NAME LOCATION RST WK DIR DESCRIPTION
SBASE:[10:0] 2519[2:0]
251A[7:0] 0 0 R/W Base temperature for limit checking
SECURE SFR B2[6] 0 0 R/W
Inhibitserasureofpage0andashaddressesabovethebeginningofCEcodeasdenedbyCE_LCTN[6:0]
(71M6541GT/42GT)orCE_LCTN[5:0](71M6541DT/41FT/42FT).AlsoinhibitsthereadofashviatheSPI
and ICE port.
SFILT 251D[3:0] 0 0 R/W Filter variable for wake on temperature extremes.
SLEEP 28B2[7] 0 0 W Puts the part to SLP mode. Ignored if system power is present. The part wakes when the Wake timer expires,
when push button is pushed, or when system power returns.
SLOT_EXT[3:0] 2112[3:0] 0 0 R/S If non-zero, will extend the duration of time slot zero by up to 15 extra crystal cycles. The ADC result for time
slotzerowillbeleft-shiftedninebitsifSLOT_EXT=0andfourbitsifSLOT_EXT≠0.
SMAX[6:0] 251B[6:0] 0 0 R/W Maximum temperature for limit checking
SMIN[6:0] 251C[6:0] 0 0 R/W Minimum temperature for limit checking
SPI_CMD[7:0] SFR FD[7:0] – – R SPI command register for the 8-bit command from the bus master.
SPI_E 270C[4] 1 1 R/W SPI port enable. Enables SPI interface on pins SEGDIO36 – SEGDIO39.
RequiresthatLCD_MAP[36-39]=0.
SPI_SAFE 270C[3] 0 0 R/W LimitsSPIwritestoSPI_CMDanda16-byteregioninDRAM.Nootherwritesarepermitted.
SPI_STAT[7:0] 2708[7:0] 0 0 R
SPI_STATcontainsthestatusresultsfromthepreviousSPItransaction.
Bit 7: Ready error: The 71M654xT was not ready to read or write as directed by the previous command.
Bit 6: Read data parity: This bit is the parity of all bytes read from the 71M654xT in the previous command.
DoesnotincludetheSPI_STATbyte.
Bit 5: Write data parity: This bit is the overall parity of the bytes written to the 71M654xT in the previous
command. It includes CMD and ADDR bytes.
Bit 4-2: Bottom 3 bits of the byte count. Does not include ADDR and CMD bytes. One, two, and three byte
instructions return 111.
Bit 1: SPI FLASH mode: This bit is zero when the TEST pin is zero.
Bit0:SPIFLASHmodeready:UsedinSPIFLASHmode.Indicatesthattheashisreadytoreceiveanother
write instruction.
STEMP[15:0] 2881[7:0]
2882[7:0] – – R The result of the temperature measurement.
SUM_SAMPS[12:8]
SUM_SAMPS[7:0]
2107[4:0]
2108[7:0] 0 0 R/W ThenumberofmultiplexercyclesperXFER_BUSYinterrupt.Maximumvalueis8191cycles.
TC_A[9:0] 2508[1:0]
2509[7:0] 0 0 R/W Temperaturecompensationfactorforquadraticcompensation.
TC_B[11:0] 250A[3:0]
205B[7:0] 0 0 R/W Temperaturecompensationfactorforquadraticcompensation.
TC_C[11:0] 289C[3:0]
289D[7:0] 0 0 R/W Temperaturecompensationfactorforquadraticcompensation.
TEMP_22[12:8]
TEMP_22[7:0]
230A[4:0]
230B[7:0] 0 – R Storage location for STEMP at 22NC. STEMP is an 11-bit word.
TEMP_BAT 28A0[4] 0 – R/W Causes VBAT to be measured whenever a temperature measurement is performed.
TEMP_BSEL 28A0[7] 0 – R/W Selectswhichbatteryismonitoredbythetemperaturesensor:1=VBAT,0=VBAT_RTC
TBYTE_BUSY 28A0[3] 0 0 R Indicates that hardware is still writing the 0x28A0 byte. Additional writes to this byte will be locked out while it
is one. Write duration could be as long as 6ms.
TEMP_PER[2:0] 28A0[2:0] 0 – R/W
Sets the period between temperature measurements. Automatic measurements can be enabled in any mode
(MSN,BRN,LCD,orSLP).TEMP_PER=0disablesautomatictemperatureupdates,inwhichcaseTEMP_
START may be used by the MPU to initiate a one-shot temperature measurement.
TEMP_PER Time (seconds)
0 No temperature updates
1-6 2(3+TEMP_PER)
7 Continuous updates
Inautomaticmode,TEMP_STARTistheindicatorforthetemperaturesensorstatus:
TEMP_START=1(temperaturesensorisbusy,cannotmeasuretemperature)
TEMP_START=0(temperaturesensorisidle,canmeasuretemperature)
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Table 13. I/O RAM Locations in Alphabetical Order (continued)
NAME LOCATION RST WK DIR DESCRIPTION
TEMP_PWR 28A0[6] 0 – R/W
Selects the power source for the temp sensor:
1=VV3P3D,0=VBAT_RTC. This bit is ignored in SLP and LCD modes, where the temp sensor is always
powered by VBAT_RTC.
TEMP_START 28B4[6] 0 0 R/W
WhenTEMP_PER=0automatictemperaturemeasurementsaredisabled,andTEMP_STARTmaybesetby
theMPUtoinitiateaone-shottemperaturemeasurement.Inautomaticmode,TEMP_STARTistheindicator
for the temperature sensor status:
TEMP_START=1(temperaturesensorisbusy,cannotmeasuretemperature)
TEMP_START=0(temperaturesensorisidle,canmeasuretemperature)
TEMP_STARTisignoredinSLPandLCDmodes.HardwareclearsTEMP_STARTwhenthetemperature
measurement is complete.
TMUX[5:0] 2502[5:0] – – R/W Selects one of 32 signals for TMUXOUT.
TMUX2[4:0] 2503[4:0] – – R/W Selects one of 32 signals for TMUX2OUT.
TMUXRA[2:0] 270A[2:0] 000 000 R/W The TMUX setting for the remote isolated sensor (71M6x01).
UMUX_SEL 2456[4] 0 0 R/W
SelectsUART1IOpins.SelectsOPT_TXandOPT_RXwhen0.SelectsSEGDIO17andSEGDIO16
when1.IfUMUX_SEL=0,SEGDIO17andSEGDIO16arestandardDIOpins,reectingthevalueLCD_
SEGDIO16[5:0]andLCD_SEGDIO17[5:0].
VREF_CAL 2704[7] 0 0 R/W Brings the ADC reference voltage out to the VREFpin.ThisfeatureisdisabledwhenVREF_DIS=1.
VREF_DIS 2704[6] 0 1 R/W Disables the internal ADC voltage reference.
VSTAT[2:0] SFR F9[2:0] – – R
This word describes the source of power and the status of VDD.
000 System Power OK. VV3P3A>3.0v. Analog modules are functional and accurate.
[V3AOK,V3OK]=11
001 System Power Low. 2.8v<VV3P3A<3.0v. Analog modules not accurate. Switchover to
batterypowerisimminent.[V3AOK,V3OK]=01
VSTAT[2:0]
010 Battery power and VDD OK. VDD>2.25v. Full digital functionality.
[V3AOK,V3OK]=00,[VDDOK,VDDgt2]=11
011
Battery power and VDD>2.0. Flash writes are inhibited. If the TRIMVDD[5] fuse is blown,
PLL_FAST(I/ORAM0x2200[4])iscleared.
[V3AOK,V3OK]=00,[VDDOK,VDDgt2]=01
101
Battery power and VDD<2.0.WhenVSTAT=101,processorisnearlyoutofvoltage.
Processor failure is imminent.
[V3AOK,V3OK]=00,[VDDOK,VDDgt2]=00
WAKE_ARM 28B2[5] 0 – R/W ArmstheWAKEtimerandloadsitwithWAKE_TMR[7:0].WhenSLEEPorLCD_ONLYisassertedbythe
MPU, the WAKE timer becomes active.
WAKE_TMR[7:0] 2880[7:0] 0 – R/W TimerdurationisWAKE_TMR+1seconds.
WD_RST 28B4[7] 0 0 W Reset the WD timer. The WD is reset when a 1 is written to this bit. Writing a one clears and restarts the
watch dog timer.
WF_DIO4 28B1[2] 0 – R DIO4wakeagbit.IfDIO4isconguredtowakethepart,thisbitissetwheneverthede-bouncedversionof
DIO4rises.ItisheldinresetifDI04isnotconguredforwakeup.
WF_DIO52 28B1[1] 0 – R DIO52wakeagbit.IfDIO52isconguredtowakethepart,thisbitissetwheneverthede-bouncedversion
ofDIO52rises.ItisheldinresetifDI052isnotconguredforwakeup.
WF_DIO55 28B1[0] 0 – R DIO55wakeagbit.IfDIO55isconguredtowakethepart,thisbitissetwheneverthede-bouncedversion
ofDIO55rises.ItisheldinresetifDI055isnotconguredforwakeup.
WF_TEMP 28B1[6] 0 – R Indicates that the temperature range check hardware caused the part to wake up.
WAKE_ARM 28B2[5] 0 – R/W ArmstheWAKEtimerandloadsitwithWAKE_TMR[7:0].WhenSLEEPorLCD_ONLYisassertedbythe
MPU, the WAKE timer becomes active.
WF_PB 28B1[3] 0 – R Indicates that the PB caused the part to wake.
WF_RX 28B1[4] 0 – R Indicates that RX caused the part to wake.
WF_CSTART
WF_RST
WF_RSTBIT
WF_OVF
WF_ERST
WF_BADVDD
28B0[7]
28B0[6]
28B0[5]
28B0[4]
28B0[3]
28B0[2]
0
1
0
0
0
0
– R Indicates that the Reset pin, Reset bit, ERST pin, Watchdog timer, the cold start detector, or
bad VBAT caused the part to reset.
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Reading the Info Page
Information useful for calibrating the temperature sensor
and other functions is available in trim fuses. The trim
fuse values provided in the 71M654xT devices cannot
be directly accessed through the I/O RAM space. They
reside in a special area termed the Info Page. The MPU
gains access to the Info Page by setting the INFO_PG
(I/O RAM 0x270B[0]) control bit. Once this bit is set, Info
Page contents are accessible in program memory space
startingattheaddressspecifiedbythecontentsofCE_
LCTN[6:0](71M654xGT)orCE_LCTN[5:0](71M654xFT)
(I/O RAM 0x2109[6:0] for 71M654xGT or 0x2109[5:0] for
71M654xFT). These pointers specify a base address at a
1KBaddressboundarywhichisat1024xCE_LCTN[6:0]
(71M654xGT)orCE_LCTN[5:0](71M654xFT).Table 14
provides a list of the available trim fuses and their corre-
sponding offsets relative to the Info Page base address.
After reading the desired Info Page information, the MPU
must reset the INFO_PG bit. The code below provides
an example for reading Info Page fuse trims. In this
code example, the address, px is a pointer to the MPU’s
code space. In assembly language, the Info Page data
objects, which are read-only, must be accessed with the
MOVC 8051 instruction. In the C language, Info Page trim
fuses must be fetched with a pointer of the correct width,
depending on the format of the trim fuse (8-bit or a 16-bit
data object). The case statements in the code example
below perform casts to obtain a pointer of the correct size
for each object, as needed.
In assembly language, the MPU has to form 11-bit or
16-bit values from two separate 8-bit fetches, depending
on the object being fetched. The byte values containing
less than 8 valid bits are LSB justified. For example Info
Page offset 0x90 is an 8-bit object, whose three LSBs are
bits[10:8]ofthecompleteTEMP_85[10:0]11-bitobject.
The Info Page data objects are 2’s complement format
and should be sign extended when read into a 16-bit data
type(seecase_TEMP85inthecodeexample).
#if HIGH_PRECISION_METER
int16_t read_trim (enum eTRIMSEL
select) {
uint8r_t *px;
int16_t x;
px = ((uint16_t)select) +
((uint8r_t *)(CE3 << 10));
switch (select)
{
default:
case _TRIMBGD:
INFO_PG = 1;
x = *px;
INFO_PG = 0;
break;
case _TRIMBGB:
INFO_PG = 1;
x = *(uint16r_t*)px;
INFO_PG = 0;
break;
case _TEMP85:
INFO_PG = 1;
x = *(uint16r_t*)px;
INFO_PG = 0;
if (x & 0x800) x |= 0xF800;
break;
}
return (x); }
#endif //#if HIGH_PRECISION_METER
Table 14. Info Page Trim Fuses
REGISTER NAME DEFINITION LOCATION ADDRESS FORMAT TYPICAL VALUE
STEMP_T85_P STEMP at +85C Info Block 0xAA, 0xAB 16 bits, signed 4400
STEMP_T22_P STEMP at +22C Info Block 0x8A, 0x8B 13 bits, unsigned 3600
T85_P Probe temperature at +85C Info Block 0xA6, 0xA7 16 bits signed 605
T22_P Probe temperature at +22C Info Block 0x9A 8 bits signed 35
STEMP Temperature sensor I/O RAM 0x2882,
0x2882 11 bits, sign extended
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Meter Calibration
Once the 71M654xT energy meter device has been
installed in a meter system, it must be calibrated. A com-
plete calibration includes:
• Establishment of the reference temperature (typically
22°C).
• Calibration of the metrology section: calibration for toler-
ances of the current sensors, voltage dividers and sig-
nal conditioning components as well as of the internal
reference voltage (VREF) at the reference temperature.
• Calibration of the oscillator frequency using RTCA_
ADJ[7:0].
The metrology section can be calibrated using the gain
and phase adjustment factors accessible to the CE. The
gain adjust ment is used to compensate for tolerances of
components used for signal conditioning, especially the
resistive components. Phase adjustment is provided to
compensate for phase shifts introduced by the current
sensors or by the effects of reactive power supplies.
Due to the flexibility of the MPU firmware, any calibration
method, such as calibration based on energy, or current
and voltage can be implemented. It is also possible to
implement segment-wise calibration (depending on cur-
rent range).
The 71M6541DT/FT/GT and 71M6542FT/GT support
common industry standard calibration techniques, such
as single-point (energy-only), multipoint (energy, VRMS,
IRMS), and autocalibration.
Contact Maxim Integrated to obtain a copy of the latest
calibration spreadsheet file for the 71M654xT.
Firmware Interface
Overview: Functional Order
The I/O RAM locations at addresses 0x2000 to 0x20FF
have sequential addresses to facilitate reading by the
MPU. These I/O RAM locations are usually modified only
atpower-up.Theseaddressesareanalternativesequen-
tial address to subsequent addresses (above 0x2100).
For instance, EQU[2:0] can be accessed at I/O RAM
0x2000[7:5] or at I/O RAM 0x2106[7:5].
Unimplemented (U) and reserved (R) bits are shaded in
light gray. Unimplemented bits are identified with a ‘U’.
Unimplemented bits have no memory storage, writing
them has no effect, and reading them always returns zero.
Reserved bits are identified with an ‘R’, and must always
be written with a zero. Writing values other than zero to
reserved bits may have undesirable side effects and must
be avoided.
Nonvolatile bits are shaded in dark gray. Nonvolatile bits
are backed up during power failures if the system includes
a battery connected to the VBAT pin.
I/O RAM Map: Details
Writable bits are written by the MPU into configuration
RAM. Typically, they are initially stored in flash memory
and copied to the configuration RAM by the MPU. Some
ofthe more frequently programmedbits are mapped to
the MPU SFR memory space. The remaining bits are
mapped to the address space 0x2XXX. The RST and WK
columns describe the bit values upon reset and wake,
respectively. No entry in one of these columns means the
bit is either read-only or is powered by the NV supply and
is not initialized. Write-only bits return zero when they are
read.
Locations that are shaded in grey are nonvolatile (i.e.,
battery-backed).
CE Interface Description
CE Program
The CE performs the precision computations necessary to
accurately measure energy. These computa tions include
offset cancellation, phase compensation, product smooth-
ing,productsummation,frequencydetection,VARcalcula-
tion, sag detection and voltage phase measurement.
The CE program is supplied by Maxim Integrated as a
data image that can be merged with the MPU operational
code for meter applications. Typically, the CE program
provided with the demonstration code covers most appli-
cations and does not need to be modified. Other varia-
tions of CE code are available. Contact your local Maxim
Integrated representative to obtain the appropriate CE
coderequiredforaspecificapplication.
CE Data Format
All CE words are 4 bytes. Unless specified otherwise,
they are in 32-bit two’s complement format
(-1=0xFFFFFFFF).Calibrationparametersaredefinedin
flash memory (or external EEPROM) and must be copied
to CE data memory by the MPU before enabling the CE.
Internal variables are used in internal CE calculations.
Input variables allow the MPU to control the behavior of
the CE code. Output variables are outputs of the CE cal-
culations. The corresponding MPU address for the most
significantbyteisgivenby0x0000+4xCE_addressand
by0x0003+4xCE_addressfortheleastsignificantbyte.
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Constants
• SamplingFrequency:2520.62Hz.
• F0:Frequencyofthemainsphases(typically50Hzor
60Hz).
• IMAX: RMS current corresponding to 250mV peak
(176.8 mVRMS) at the inputs IA and IB. IMAX needs
to be adjusted if the preamplifier is activated for the
IAP-IAN inputs. For a 250μΩ shunt resistor, IMAX
becomes707A(176.8mVRMS/250FI=707.2ARMS).
• VMAX: RMS voltage corresponding to 250mV peak at
the VA and VB inputs.
• NACC: Accumulation count for energy measurements
is SUM_SAMPS[12:0]. The duration of the accumu-
lation interval for energy measurements is SUM_
SAMPS[12:0]/FS.
• X: Gain constant of the pulse generators. Its value is
determinedbyPULSE_FASTandPULSE_SLOW.
• Voltage LSB (for sag threshold) = VMAX x 7.8798
x10-9 V.
The system constants IMAX and VMAX are used by the
MPUtoconvertinternaldigitalquantities(asusedbythe
CE)toexternal,i.e.,meteringquantities.Theirvaluesare
determined by the scaling of the voltage and current sen-
sors used in an actual meter.
Environment
Before starting the CE using the CE_E bit (I/O RAM
0x2106[0]), the MPU has to establish the proper environ-
ment for the CE by implementing the following steps:
• Locate the CE code in flash memory using
CE_LCTN[5:0] (71M6541DT/41FT/42FT) or CE_
LCTN[6:0] (71M6541GT/42GT).
• Load the CE data into RAM.
• EstablishtheequationtobeappliedinEQU[2:0].
• Establish the number of samples per accumulation
periodinSUM_SAMPS[12:0].
• Establish the number of cycles per ADC multiplexer
frame(MUX_DIV[3:0]).
• ApplypropervaluestoMUXn_SEL,aswellasproper
selectionsforDIFFn_EandRMT_Einordertoconfig-
ure the analog inputs.
• Initialize any MPU interrupts, such as CE_BUSY,
XFER_BUSY,orthepowerfailuredetectioninterrupt.
• VMAX=600V,IMAX=707A,andkH=1Wh/pulseare
assumed as default settings
When different CE codes are used, a different set of envi-
ronment parameters need to be established. The exact
values for these parameters are listed in the Application
Notes and other documentation which accompanies the
CE code.
The CE details described in this data sheet should
be considered typical and may not, in aggregate, be
indicative of any particular CE code. Contact your Maxim
Integrated representative for details about available stan-
dard CE codes.
CE Calculations
The MPU selects the basic configuration for the CE by
setting the EQU variable.
CE Input Data
Data from the AFE is placed into CE memory by hard-
ware at ADC0-ADC3 and ADC9 and ADC10. Table 16
describes the process.
CE Status and Control
The CESTATUS register (0x80) contains bits that reflect
the status of the signals that are applied to the CE.
CECONFIG (0x20) contains bits that control basic opera-
tion of the compute engine.
The CE code supports registers to establish the sag
threshold and gain for each of the input channels. When
the input RMS voltage level falls below an established
level, a warning is posted to the MPU. This level is called
thesagthreshold,anditissetintheSAG_THRregister.
Gain for each channel is adjusted in the GAIN_ADJ0
(voltage), GAIN_ADJ1 (current channel A) and GAIN_
ADJ2 (current channel B).
Transfer Variables
After each pass through CE program code, the CE
assertsa XFER_BUSYinterrupt.This informs theMPU
that new data is available. It is the responsibility of MPU
code to retrieve the data from the CE in a timely manner.
Pulse Generation
WRATE (CE RAM 0x21) along with the PULSE_SLOW
andPULSE_FASTbitscontrolthenumberofpulsesthat
are generated per measured Wh and VARh quantities.
The pulse rate is proportional to the WRATE value for
a given energy. The meter constant Kh is derived from
WRATE as the amount of energy measured for each
pulse.Thatis,ifKh=1Wh/pulse,apowerappliedtothe
meterof120Vand30Aresultsinonepulsepersecond;
if the load is 240 V at 150 A, ten pulses per second are
generated.
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Table 15. Power Equations
†71M6542FT/GT only.
Table 16. CE Raw Data Access Locations
*Remote interface data.
†71M6542FT/GT only.
Normally, the CE takes the values from W0SUM_X
and VAR0SUM_X and moves them to APULSEW and
APULSER, respectively. Then, pulse generation logic in
the CE creates the actual pulses. However, the MPU can
take direct control of the pulse generation process by
settingEXT_PULSE=1.Inthiscase,theMPUsetsthe
pulse rate by directly loading APULSEW and APULSER.
Note that since creep management is an MPU function,
whentheCEmanages pulse output (EXT_PULSE=0)
creep management is disabled.
The maximum pulse rate is 3 x FS=7.56kHz.
The maximum time jitter is 1/6 of the multiplexer cycle
period(nominally67μs)andisindependentofthenum-
ber of pulses measured. Thus, if the pulse generator is
monitored for one second, the peak jitter is 67ppm. After
10 seconds, the peak jitter is 6.7ppm. The average jit-
ter is always zero. If it is attempted to drive either pulse
generator faster than its maximum rate, it simply outputs
at its maximum rate without exhibiting any rollover char-
acteristics. The actual pulse rate, using WSUM as an
example, is:
S
46
WRATE WSUM F X
RATE Hz
2
⋅ ⋅⋅
=
where FS=samplingfrequency(2520.6Hz),X=Pulse
speed factor derived from the CE variables PULSE_
SLOWandPULSE_FAST.
CE Flow Diagrams
Figure 24, Figure 25, and Figure 26 show the data flow
through the CE in simplified form. Functions not shown
include delay compensation, sag detection, scaling, and
theprocessingofmeterequations.
EQU Watt & VAR Formula
(WSUM/VARSUM)
Inputs Used for Energy/Current Calculation
W0SUM/
VAR0SUM
W1SUM/
VAR1SUM
I0SQ
SUM
I1SQ
SUM
0 VA IA - 1 element, 2W 1fVA x IA VA x IB IA –
1 VA x (IA-IB)/2 - 1 element, 3W 1fVA x (IA-IB)/2 – IA-IB IB
2†VA x IA + VB x IB - 2 element, 3W 3f Delta VA x IA VB x IB IA IB
ADC LO CATION PIN MUX_SEL HANDLE CE RAM LOCATION
DIFFA_E DIFFA_E
0 1 0 1
ADC0 IAP 0 000
ADC1 IAP 1 1
RMT_E, DIFFB_E RMT_E, DIFFB_E
0,0 0,1 1,0 1,1 0,0 0,1 1,0 1,1
ADC2 IBP 2 2––22 2* 2*
ADC3 IBN 3 3
TherearenocongurationbitsforADC9,10
ADC9 VB† 9 9
ADC10 VA 10 10
CE Flow Diagrams
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Table 17. CE Status Register
Table 18. CE Configuration Register
CESTATUS bit Name Description
31:4 Not Used These unused bits are always zero.
3F0 F0isasquarewaveattheexactfundamentalinputfrequency.
2 Not Used This unused bit is always zero.
1SAG_B Normally zero. Becomes one when VB remains below SAG_THR for SAG_CNT samples.
Does not return to zero until VB rises above SAG_THR.
0SAG_A Normally zero. Becomes one when VA remains below SAG_THR for SAG_CNT samples.
Does not return to zero until VA rises above SAG_THR.
CECONFIG BIT NAME DEFAULT DESCRIPTION
22 EXT_TEMP 0When1,theMPUcontrolstemperaturecompensationviatheGAIN_ADJn
registers (CE RAM 0x40-0x42), when 0, the CE is in control.
21 EDGE_INT 1When 1, XPULSE produces a pulse for each zero-crossing of the mains phase
selected by FREQSEL[1:0] , which can be used to interrupt the MPU.
20 SAG_INT 1 When 1, activates YPULSE output when a sag condition is detected.
19:8 SAG_CNT 252
(0xFC)
The number of consecutive voltage samples below SAG_THR (CE RAM 0x24)
beforeasagalarmisdeclared.Thedefaultvalueisequivalentto100ms.
7:6 FREQSEL[1:0] 0
FREQSEL[1:0]selectsthephasetobeusedforthefrequencymonitor,sag
detection, and for the zero crossing counter (MAINEDGE_X).
FREQ SEL[1:0] Phase Se lected
0 0 A
0 1 B*
1 X Not allowed
*71M6542FT/GT only
5EXT_PULSE 1
Whenzero,causesthepulsegeneratorstorespondtointernaldata(WPULSE=
WSUM_X,VPULSE=VARSUM_X). Otherwise, the generators respond to values
the MPU places in APULSEW and APULSER.
4:2 Reserved 0 Reserved.
1PULSE_FAST 0
When PULSE_FAST=1,thepulsegeneratorinputisincreased16x.When
PULSE_SLOW=1,thepulsegeneratorinputisreducedbyafactorof64.These
two parameters control the pulse gain factor X (see table below). Allowed values
areeither1or0.Defaultis0forboth(X=6).
0PULSE_SLOW 0
PULSE_FAST PULSE_SLOW X
00 1.5 x 22=6
10 1.5 x 26=96
01 1.5 x 2-4=0.09375
11 Do not use
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Table 19. Sag Threshold and Gain Adjustment Registers
†71M6542FT/GT only.
Table 20. CE Transfer Registers
CE ADDRESS NAME DEFAULT DESCRIPTION
0x24 SAG_THR 2.39 x 107
Thevoltagethresholdforsagwarnings.Thedefaultvalueisequivalentto113V
peakor80VRMSifVMAX=600VRMS.
RMS
9
V2
SAG_THR
VMAX 7.8798 10
−
⋅
=
⋅⋅
0x40 GAIN_ADJ0 16384
This register scales the voltage measurement channels VA and VB*. The default
valueof16384isequivalenttounitygain(1.000).
*71M6542FT/GT only
0x41 GAIN_ADJ1 16384 This register scales the IA current channel for Phase A. The default value of 16384
isequivalenttounitygain(1.000).
0x42 GAIN_ADJ2 16384 This register scales the IB current channel for Phase B. The default value of
16384isequivalenttounitygain(1.000).
CE ADDRESS NAME DESCRIPTION
0x84† WSUM_X Thesignedsum:W0SUM_X+W1SUM_X.NotusedforEQU[2:0]=0andEQU[2:0]=1.
0x85 W0SUM_X The sum of Wh samples from each wattmeter element.
LSB=9.4045x10-13 x VMAX x IMAX Wh (local)
LSB=1.55124x10-12 x VMAX x IMAX Wh (remote)
0x86 W1SUM_X
0x88† VARSUM_X Thesignedsum:VAR0SUM_X+VAR1SUM_X.NotusedforEQU[2:0]=0andEQU[2:0]=1.
0x89 VAR0SUM_X The sum of VARh samples from each wattmeter element.
LSB=9.4045x10-13 x VMAX x IMAX VARh (local)
LSB=1.55124x10-12 x VMAX x IMAX VARh (remote)
0x8A VAR1SUM_X
0x8C I0SQSUM_X Thesumofsquaredcurrentsamplesfromeachelement.
LSB=9.9045x10-13 IMAX2 A2h (local)
LSB=2.55872x10-12 x IMAX2 A2h (remote)
WhenEQU=1,I0SQSUM_XisbasedonIAandIB.
0x8D I1SQSUM_X
0x90 V0SQSUM_X Thesumofsquaredvoltagesamplesfromeachelement.
LSB=9.4045x10-13 VMAX2 V2h (local)
LSB=9.40448x10-13 x VMAX2 V2h (remote)
0x91† V1SQSUM_X
0x82 FREQ_X
Fundamentalfrequency:
6
32
6
32
2520.6Hz
LSB 0.509 10 Hz (for Local)
2
2520.6Hz
LSB 0.587 10 Hz (for Remote)
2
−
−
≡ ≈⋅
≡ ≈⋅
0x83 MAINEDGE_X The number of edge crossings of the selected voltage in the previous ac cumulation interval.
Edge crossings are either direction and are debounced.
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Table 21. CE Pulse Generation Parameters
CE ADDRESS NAME DEFAULT DESCRIPTION
0x21 WRATE 547
ACC
VMAX IMAX K
Kh Wh / pulse
WRATE N X
⋅⋅
= ⋅
⋅⋅
where:
K=66.1782(LocalSensors)
K=109.1587(RemoteSensor)
NACC=SUM_SAMPS[12:0] (CE RAM 0x23)
XisafactordeterminedbyPULSE_FASTandPULSE_SLOW.See
CECONFIGdenitionformoreinformation
Thedefaultvalueyields1.0Wh/pulseforVMAX=600VandIMAX=208
A. The maximum value for WRATE is 32,768 (215).
0x22 KVAR 6444 Scale factor for VAR measurement.
0x23 SUM_SAMPS 2520 SUM_SAMPS (NACC).
0x45 APULSEW 0
Wh pulse (WPULSE) generator input to be updated by the MPU when
using external pulse generation. The output pulse rate is:
APULSEW * FS * 2-32 * WRATE * X * 2-14.
This input is buffered and can be updated by the MPU during a conversion
interval. The change takes effect at the beginning of the next interval.
0x46 WPULSE_CTR 0 WPULSE counter.
0x47 WPULSE_FRAC 0Unsigned numerator, containing a fraction of a pulse. The value in this
register always counts up towards the next pulse.
0x48 WSUM_ACCUM 0 Roll-over accumulator for WPULSE.
0x49 APULSER 0 VARh (VPULSE) pulse generator input.
0x4A VPULSE_CTR 0 VPULSE counter.
0x4B VPULSE_FRAC 0Unsigned numerator, containing a fraction of a pulse. The value in this
register always counts up towards the next pulse.
0x4C VSUM_ACCUM 0 Roll-over accumulator for VPULSE.
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Table 22. Other CE Parameters
CE ADDRESS NAME DEFAULT DESCRIPTION
0x25 QUANT_VA 0
Compensation factors for truncation and noise in voltage, current, real energy
and reactive energy for phase A.
0x26 QUANT_IA 0
0x27 QUANT_A 0
0x28 QUANT_VARA 0
0x29 † QUANT_VB 0
Compensation factors for truncation and noise in voltage, current, real energy
and reactive energy for phase B.
† 71M6542FT/GT only.
0x2A QUANT_IB 0
0x2B QUANT_B 0
0x2C QUANT_VARB 0
0x38 0x43453431 CElenameidentierinASCIIformat(CE41a01f).Thesevaluesare
overwritten as soon as the CE starts
0x39 0x6130316B
0x3A 0x00000000
LSB weights for use with Local Sensors:
QUANT_Ix_LSB=5.08656·10-13 ∙ IMAX2 (Amps2)
QUANT_Wx_LSB=1.04173·10-9 ∙ VMAX ∙ IMAX (Watts)
QUANT_VARx_LSB=1.04173·10-9 ∙ VMAX ∙ IMAX (Vars)
LSB weights for use with the 71M6x01 isolated sensors:
QUANT_Ix_LSB=1.38392·10-12 ∙ IMAX2 (Amps2)
QUANT_Wx_LSB=1.71829·10-9 ∙ VMAX ∙ IMAX (Watts)
QUANT_VARx_LSB=1.71829·10-9 ∙ VMAX ∙ IMAX (Vars)
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Table 23. CE Calibration Parameters
Figure 24. CE Data Flow—Multiplexer and ADC
CE ADDRESS NAME DEFAULT DESCRIPTION
0x10 CAL_IA 16384 These constants control the gain of their respective channels. The nominal
value for each parameter is 214 =16384.Thegainofeachchannelisdirectly
proportional to its CAL parameter. Thus, if the gain of a channel is 1% slow, CAL
should be increased by 1%. Refer to the 71M6541 Demo Board User’s Manual for
theequationstocalculatethesecalibrationparameters.
† 71M6542FT/GT only.
0x11 CAL_VA 16384
0x13 CAL_IB 16384
0x14†CAL_VB 16384
0x12 PHADJ_A 0
These constants control the CT phase compensation. Com pensation does not
occur when PHADJ_X=0.AsPHADJ_X is increased, more compensation (lag) is
introduced. The range is P 215 – 1. If it is desired to delay the current by the angle
F,theequationsare:
20 0.02229 tan(
PHADJ_X 2 0.1487 0.0131 tan(
⋅ F)
=− ⋅ F)
at 60Hz
20
0.0155 tan(
PHADJ_X 2
0.1241 0.009695 tan(
⋅ F)
=− ⋅ F)
at 50Hz
0x15 PHADJ_B 0
0x12 L_COMP2_A 16384
Theshuntdelaycompensationisobtainedusingtheequationprovidedbelow:
where:
( )
( )
( )
( )
( )
( )
SS
SS
sin 2 f f tan 1-cos 2 f f
L_COMP2_X=16384× sin 2 f f tan cos 2 f f

π + θ× π

π + θ× π
fS=samplingfrequency
f=mainfrequency
0x15 L_COMP2_B 16384
DECIMATOR
I0_RAW
DE-MULTIPLEXER
∆∑
MOD
VREF
F
CLK
= 4.9152MHz
F
S
= 2520Hz
(ON EACH CHANNEL)
V0_RAW
I1_RAW
I0
MULTIPLEXER
V0
I1
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Figure 25. CE Data Flow—Offset, Gain, and Phase Compensation
Figure 26. CE Data Flow—Squaring and Summation
OFFSET
NULL
CAL_I0
PHASE
COMP LPF W0
LPF VAR0
LPF VAR1
90°
I0
PHADJ_0
F0
I0_RAW
OFFSET
NULL
CAL_V0
V0
CAL_I1 GAIN_ADJ
F0
V0_RAW
OFFSET
NULL
PHASE
COMP LPF W1
I1
F0
F0
GENERATOR
PHADJ_1
F0
I1_RAW
∑W0 W0SUM_X
∑W1 W1SUM_X
∑VAR0 VAR0SUM_X
∑
SUM
∑I0SQSUM_X
∑V0SQSUM_X
∑I1SQSUM_X
I0SQ
V0SQ
I1SQ
SUM
I
2
V
2
I
2
I0
V0
I1
F0
SQUARE
MPU
VAR1 VAR1SUM_X
SUM_SAMS = 2520
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Ordering Information
F = Lead(Pb)-free/RoHS-compliant package.
R = Tape and reel.
Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
PART TEMP RANGE ACCURACY (typ, %) FLASH (KB) PIN-PACKAGE
71M6541DT-IGT/F -40°C to +85°C 0.1 32 64 LQFP
71M6541DT-IGTR/F -40°C to +85°C 0.1 32 64 LQFP
71M6541FT-IGT/F -40°C to +85°C 0.1 64 64 LQFP
71M6541FT-IGTR/F -40°C to +85°C 0.1 64 64 LQFP
71M6541GT-IGT/F -40°C to +85°C 0.1 128 64 LQFP
71M6541GT-IGTR/F -40°C to +85°C 0.1 128 64 LQFP
71M6542FT-IGT/F -40°C to +85°C 0.1 64 100 LQFP
71M6542FT-IGTR/F -40°C to +85°C 0.1 64 100 LQFP
71M6542GT-IGT/F -40°C to +85°C 0.1 128 100 LQFP
71M6542GT-IGTR/F -40°C to +85°C 0.1 128 100 LQFP
PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.
64 LQFP C64L+7 21-0665 90-0411
100 LQFP C100L+8 21-0684 90-0416
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Typical Operating Circuit
MPU
RTC
TIMERS
IAP
VA
IBP
XIN
XOUT
RX
TX
TX
RX
COM0...5
V3P3A V3P3SYS
VBAT
VBAT_RTC
SEG
GNDA GNDD
SEG/DIO
DIO
ICE
LINE
NEUTRAL
LOAD
PULSES,
DIO
IR
AMR
POWER FAULT
COMPARATOR
MODULATOR
SERIAL PORTS
OSCILLATOR/PLL
MUX AND ADC
LCD DRIVER
DIO, PULSES
COMPUTE
ENGINE
FLASH MEMORY
RAM
32 kHz
REGULATOR
SHUNT
SHUNT
POWER SUPPLY
71M6541DT
71M6541FT
71M6541GT
TEMPERATURE
SENSOR
VREF
BATTERY
RTC
BATTERY
PWR MODE
CONTROL
WAKE-UP
NEUTRAL
I2C OR µWire
EEPROM
IAN
IBN
V3P3D
BATTERY
MONITOR
SPI INTERFACE
HOST
LCD DISPLAY
RESISTOR DIVIDER
PULSE
TRANSFORMER
LINE
LINE
NOTE: THIS SYSTEM IS REFERENCED TO LINE.
71M6xx1
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
71M6541DT/71M6541FT/71M6541GT/
71M6542FT/71M6542GT
Energy Meter ICs
© 2015 Maxim Integrated Products, Inc.
│
78
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 12/12 Initial release —
1 8/13
Addednoteaboutlimits,updatedtheVBAT_RTCcurrentandashwritecurrent
specication,replacedtemperaturemeasurementequationformula,corrected
parameter name in the Internal Power Fault Comparator section, added Notes 1 and
2totheElectricalCharacteristicstable,updatedTable12withdenitionsforSTEMP_
T22_P,STEMP_T85_P,T22_P,andT85_PandUMUX_SELdescription,added
descriptionandspecicationsfor71M6541GTand71M6542GT,addednoteintheSPI
Flash Modesectionaboutcodeupdates,correctedpartnumberingures,updated
Table 12 for the external interrupts, changed the single-ended inputs from four to two,
updatedthedescriptionofTEMP_STARTandTEMP_PERinTable12,updatedthe
descriptionofCHIP_IDinTable12,andaddeddescriptionfortheUARTs section
1–74
2 10/13 Removed future product status on 71M6541DT and 71M6541FT in the Ordering
Information table 72
3 12/13 Updated the CXL and CXS capacitor values from 10pF and 15pF to 22pF 12, 15
4 2/14
Updated the VREFcoefcientsintheElectrical Characteristicstable;removedNote
2fromtheECnotes;changedCXSandCXLnotesintheRecommended External
Components table;removedfutureproductstatuson71M6541GTintheOrdering
Information table
8, 10, 12, 72
5 1/15 Updated the Benets and Features section 1
6 12/15
InsertedTable11(TMUXtable);updatedMetrology Temperature Compensation
section;updatedI/ORAMLocationsinAlphabeticalOrderTable;insertednew
Reading the Info Page sectionandTable;updatedtablenumbersasneeded;
corrected land pattern numbers
41, 49, 55
63, 64, 78