71M6541D Datasheet, PDF (130/166 Pages) Maxim Integrated Products – 0.1% Accuracy Over 2000:1 Current Range Energy Meter ICs

71M6541D/F/G and 71M6542F/G Data Sheet
When the MPU receives the XFER_BUSY interrupt, it knows that fresh data is available in the transfer
variables. CE transfer variables are modified during the CE code pass that ends with an XFER_BUSY
interrupt. They remain constant throughout each accumulation interval. In this data sheet, the names of
CE transfer variables always end with “_X”. The transfer variables can be categorized as:
• Fundamental energy measurement variables
• Instantaneous (RMS) values
• Other measurement parameters
5.3.8.1 Fundamental Energy Measurement Variables
Table 85 and Table 86 describe each transfer variable for fundamental energy measurement. All
variables are signed 32-bit integers. Accumulated variables such as WSUM are internally scaled so they
have at least 2x margin before overflow when the integration time is one second. Additionally, the hardware
does not permit output values to fold back upon overflow.
Table 85: CE Transfer Variables (with Local Sensors)
CE
Address
0x84^†
Name
WSUM_X
0x85
0x86
W0SUM_X
W1SUM_X
0x88^†
0x89
0x8A
VARSUM_X
VAR0SUM_X
VAR1SUM_X
Note:
† _{71M6542 only.}
Description
The signed sum: W0SUM_X+W1SUM_X. Not used
for EQU[2:0] = 0 (I/O RAM 0x2106[7:5]) and
EQU[2:0] = 1.
The sum of Wh samples from each wattmeter
element.
LSB_W = 9.4045*10^-13 * VMAX * IMAX Wh.
The signed sum: VAR0SUM_X+VAR1SUM_X. Not
used for EQU[2:0] = 0 and EQU[2:0] = 1.
The sum of VARh samples from each wattmeter
element.
LSB_W = 9.4045*10^-13 * VMAX * IMAX VARh.
Configuration
Figure 35 (page 93)
Figure 37 (page 95)
Table 86: CE Transfer Variables (with Remote Sensor)
CE
Address
0x84^†
0x85
0x86
Name
WSUM_X
W0SUM_X
W1SUM_X
0x88^†
0x89
0x8A
VARSUM_X
VAR0SUM_X
VAR1SUM_X
Note:
† _{71M6542 only.}
Description
The signed sum: W0SUM_X+W1SUM_X. Not used
for EQU[2:0] = 0 (I/O RAM 0x2106[7:5]) and
EQU[2:0] = 1.
The sum of Wh samples from each wattmeter
element.
LSB = 1.55124*10^-12 * VMAX* IMAX Wh.
The signed sum: VAR0SUM_X+VAR1SUM_X. Not
used for EQU[2:0] = 0 and EQU[2:0] = 1.
The sum of VARh samples from each wattmeter
element.
LSB = 1.55124*10^-12 *VMAX* IMAX VARh.
Configuration
Figure 36 (page 94)
Figure 38 (page 96)
WSUM_X (CE RAM 0x84) and VARSUM_X (CE RAM 0x88) are the signed sum of Phase-A and Phase-B Wh
or VARh values according to the metering equation specified in the I/O RAM control field EQU[2:0] (I/O
RAM 0x2106[7:5]). WxSUM_X (x = 0 or 1, CE RAM 0x85 and 0x86) is the Wh value accumulated for phase x
in the last accumulation interval and can be computed based on the specified LSB value.