71M6513/71M6513H
3-Phase Energy Meter IC
A Maxim Integrated Products Brand
DATA SHEET
SEPTEMBER 2011
CE Program and Environment
CE Program
The CE program is supplied by Teridian as a data image that can be merged with the MPU operational code for meter
applications. Typically, the CE program covers most applications and does not need to be modified.
Formats
All CE words are 4 bytes. Unless specified otherwise, they are in 32-bit two’s complement (-1 = 0xFFFFFFFF). ‘Calibration’
parameters are defined in flash memory (or external EEPROM) and must be copied to CE 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 calculations. The corresponding MPU address for the most
significant byte is given by 0x1000 + 4 x CE_address and 0x1003 + 4 x CE_address for the least significant byte.
Constants
Constants used in the CE Data Memory tables are:
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Sampling frequency: FS = 32768Hz/13 = 2520.62Hz.
F0 is the fundamental signal frequency, typically 50 or 60Hz.
IMAX is the external rms current corresponding to 250mV peak at the inputs IA, IB, IC.
VMAX is the external rms voltage corresponding to 250mV peak at the inputs VA, VB, VC.
NACC, the accumulation count for energy measurements is PRE_SAMPS*SUM_CYCLES. This value resides in
SUM_PRE (CE address 36).
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Accumulation count time for energy measurements is PRE_SAMPS*SUM_CYCLES/FS.
In_8 is a gain constant of current channel n. Its value is 8 or 1 and is controlled by In_SHUNT.
X is a gain constant of the pulse generators. Its value is determined by PULSE_FAST and PULSE_SLOW.
Voltage LSB = VMAX * 7.879810-9 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 sensors used in an
actual meter. The LSB values used in this document relate digital quantities at the CE or MPU interface to external meter input
quantities. For example, if a SAG threshold of 80V peak is desired at the meter input, the digital value that should be pro-
grammed into SAG_THR would be 80V/SAG_THRLSB, where SAG_THRLSB is the LSB value in the description of SAG_THR.
The parameters EQU, CE_EN, PRE_SAMPS, and SUM_CYCLES are essential to the function of the CE and are stored in I/O
RAM (see I/O RAM section).
Environment
Before starting the CE using the CE_EN bit, the MPU has to establish the proper environment for the CE by implementing the
following steps:
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Loading the image for the CE code into CE PRAM.
Loading the CE data into CE DRAM.
Establishing the equation to be applied in EQU.
Establishing the accumulation period and number of samples in PRE_SAMPS and SUM_CYCLES.
Establishing the number of cycles per ADC mux cycle.
There must be thirteen 32768Hz cycles per ADC mux cycle (see System Timing Diagram, Figure 13). This means that the
product of the number of cycles per ADC conversion and the number of conversions per cycle must be 12 (allowing for one
settling cycle). The default configuration is FIR_LEN = 0 (two cycles per conversion) and MUX_DIV = 0 (6 conversions per mux
cycle).
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