Rainbow Electronics 71M6542G - Manual (Page 130)

130 © 2008–2011 Teridian Semiconductor Corporation v1.1
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
Name Description Configuration
0x84
†
WSUM_X
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.
Figure 35 (page 93 )
Figure 37 (page 95 )
0x85 W0SUM_X The sum of Wh samples from each wattmeter
element.
LSB
W
= 9.4045*10
-13
* VMAX * IMAX Wh.
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
W
= 9.4045*10
-13
* VMAX * IMAX VARh.
0x8A VAR1SUM_X
Note:
† 71M6542 only.
Table 86: CE Transfer Variables (with Remote Sensor)
CE
Address
Name Description Configuration
0x84
†
WSUM_X
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.
Figure 36 (page 94 )
Figure 38 (page 96 )
0x85 W0SUM_X The sum of Wh samples from each wattmeter
element.
LSB = 1.55124*10
-12
* VMAX* IMAX Wh.
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 = 1.55124*10 -12 *VMAX* IMAX VARh.
0x8A VAR1SUM_X
Note:
†
71M6542 only.
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.