Data Sheet 71M6531D/F-71M6532D/F
FDS 6531/6532 005
4.3.7 CE Transfer Variables
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:
1. Fundamental energy measurement variables
2. Instantaneous (RMS) values
3. Other measurement parameters
Fundamental Energy Measurement Variables
Table 61 describes 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 will not permit
output values to fold back upon overflow.
Table 61: CE Transfer Variables
CE
Name
Description
Address
For EQU[2:0] = 2, this register holds the calculated sum of Wh samples
from each wattmeter element (In_8 is the gain of 1 or 8 configured by
IA_SHUNT or IB_SHUNT).
WSUM_X
0x85
LSB = 6.6952*10-13 VMAX IMAX / In_8 Wh.
W0SUM_X
W1SUM_X
The sum of Wh samples from each wattmeter element (In_8 is the gain
of 1 or 8 configured by IA_SHUNT or IB_SHUNT).
0x86
0x87
LSB = 6.6952*10-13 VMAX IMAX / In_8 Wh.
For EQU[2:0] = 2, this register holds the calculated sum of VARh
samples from each element (In_8 is the gain of 1 or 8 configured by
IA_SHUNT or IB_SHUNT).
VARSUM_X
0x8A
LSB = 6.6952*10-13 VMAX IMAX / In_8 VARh.
VAR0SUM_X
VAR1SUM_X
The sum of VARh samples from each element (In_8 is the gain 1 or 8
configured by IA_SHUNT or IB_SHUNT).
0x8B
0x8C
LSB = 6.6952*10-13 VMAX IMAX / In_8 VARh.
WxSUM_X is the Wh value accumulated for element X in the last accumulation interval and can be computed
based on the specified LSB value.
For example, with VMAX = 600 V and IMAX = 208 A, the LSB for WxSUM_X is 0.08356 µWh.
Instantaneous Measurement Variables
Table 62 contains various measurement results. The Frequency measurement is computed for the phase
selected with FREQSELn bits in the CECONFIG register.
IxSQSUM_X and VxSQSUM are the squared current and voltage samples acquired during the last accumulation
interval. They can be used to calculate RMS voltages and currents. INSQSUM_X can be used for computing
the neutral current.
Table 62: CE Energy Measurement Variables
CE
Name
Description
Address
Fundamental frequency.
FS
232
0x82
FREQ_X
≈ 0.587 ⋅10−6
LSB
Hz
≡
0x8F
I0SQSUM_X
The sum of squared current samples from each element.
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