71m6521be Maxim Integrated Products, Inc., 71m6521be Datasheet - Page 79

• Manufacturer Part Number: 71m6521be
• Description: Energy Meter Ic
• Manufacturer: Maxim Integrated Products, Inc.

CE TRANSFER VARIABLES
When the MPU receives the XFER_BUSY interrupt, it knows that fresh data is available in the transfer variables.
The table below 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 1 second. Additionally, the hardware will not permit output values to ‘fold back’ upon overflow.
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 = 600V and IMAX = 208A, LSB (for WxSUM_X) is 0.08356 µWh.
The Frequency measurement is computed using the Frequency locked loop for the selected phase.
IxSQSUM_X and VxSQSUM are the squared current and voltage samples acquired during the last accumulation interval.
INSQSUM_X can be used for computing the neutral current.
V1.0
Address
Address
0x11D8
0x11C8
0x11DC
0x11CC
0x11E4
0x11E0
0x11D0
0x11D4
0x11C4
0x11F0
0x11F4
CE
CE
WSUM_ACCUM
MAINEDGE_X
W0SUM_X
W1SUM_X
V0SQSUM_X
V1SQSUM_X
I0SQSUM_X
I1SQSUM_X
I0SQRT_X
I1SQRT_X
Name
FREQ_X
Name
Description
The sum of Watt samples from each wattmeter element (In_8 is the gain
configured by IA_SHUNT or IB_SHUNT).
LSB = 6.6952*10
Instantaneous Energy Measurement Variables
Description
Fundamental frequency. LSB
The number of zero crossings of the selected voltage in the previous ac-
cumulation interval. Zero crossings are either direction and are de-
bounced.
The sum of squared current samples from each element.
LSB = 6.6952*10
The sum of squared voltage samples from each element.
LSB= 6.6952*10
Rollover accumulator for WPULSE.
RMS current determined by calculating the square root of I0SQSUM_X
and I1SQSUM_X
© 2005-2008 TERIDIAN Semiconductor Corporation
Fundamental Energy Measurement Variables
-13
-13
-13
VMAX IMAX / In_8 Wh.
VMAX
IMAX
2
2
V
/ In_8
2
h
≡
2
2
F
A
32
S
2
h
≈
. 0
587
⋅
10
Energy Meter IC
−
6
Hz
71M6521BE
DATA SHEET
JANUARY 2008
Page: 79 of 97