71m6521be Maxim Integrated Products, Inc., 71m6521be Datasheet - Page 77

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

CE Calculations
The CE performs the precision computations necessary to accurately measure energy. These computations include offset
cancellation, products, product smoothing, product summation, frequency detection, and sag detection. All data computed by
the CE is dependent on the selected meter equation as given by EQU (in I/O RAM). However, for the 6521BE CE code, EQU is
always 0.
CESTATUS
Since the CE_BUSY interrupt occurs at 2520.6Hz, it is desirable to minimize the computation required in the interrupt handler
of the MPU. The MPU can read the CE status word at every CE_BUSY interrupt.
The CE Status Word is used for generating early warnings to the MPU. It contains sag warnings for VA as well as the F0 bit, a
clock derived from the fundamental input frequency. CESTATUS provides information about the status of voltage and input AC
signal frequency, which are useful for generating early power fail warnings, e.g. to initiate necessary data storage. CESTATUS
represents the status flags for the preceding CE code pass (CE busy interrupt). Sag alarms are not remembered from one
code pass to the next. The CE Status word is refreshed at every CE_BUSY interrupt.
The significance of the bits in CESTATUS is shown in the table below:
V1.0
CESTATUS
Address
0x11E8
31-29
24-0
[bit]
28
27
26
25
CE
EQU
0
VA IA (1 element, 2W 1φ)
with tamper detection
Not Used
Not Used
CESTATUS
CREEP
SAG_B
SAG_A
Name
Name
F0
Watt Formula
(WSUM)
Description
These unused bits will always be zero.
F0 is a square wave at the exact fundamental input frequency.
Normally zero. Becomes one when creep logic has been applied to either WA or WB.
Normally zero. These bits come one when the voltage in the respective channel remains
below SAG_THR for SAG_CNT samples. Will not return to zero until the voltage rises above
SAG_THR.
These unused bits will always be zero.
Description
See description of CE status word below
© 2005-2008 TERIDIAN Semiconductor Corporation
Mains Signal
Mains Signal
W0SUM
VA*IA
F0
F0
W1SUM
Element Input Mapping
VA*IB
Energy Meter IC
I0SQSUM
IA
71M6521BE
DATA SHEET
I1SQSUM
JANUARY 2008
Page: 77 of 97
IB