71M6521DE Datasheet, PDF (14/107 Pages) Teridian Semiconductor Corporation – Energy Meter IC

71M6521DE/DH/FE Data Sheet
The CE DRAM contains 128 32-bit words. The MPU can read and write the CE DRAM as the primary means of data
communication between the two processors.
Table 2 shows the CE DRAM addresses allocated to analog inputs from the AFE.
ADDRESS (HEX)
00
01
02
03
04
05
06
07
NAME
IA
VA
IB
VB
-
-
TEMP
VBAT
DESCRIPTION
Phase A current
Phase A voltage
Phase B current
Phase B voltage
Not used
Not used
Temperature
Battery Voltage
Table 2: CE DRAM Locations for ADC Results
The CE of the 71M6521DE/DH/FE is aided by support hardware that facilitates implementation of equations, pulse
counters, and accumulators. This support hardware is controlled through I/O RAM locations EQU (equation assist),
DIO_PV and DIO_PW (pulse count assist), and PRE_SAMPS and SUM_CYCLES (accumulation assist). PRE_SAMPS
and SUM_CYCLES support a dual level accumulation scheme where the first accumulator accumulates results from
PRE_SAMPS samples and the second accumulator accumulates up to SUM_CYCLES of the first accumulator results.
The integration time for each energy output is PRE_SAMPS * SUM_CYCLES/2520.6 (with MUX_DIV = 1). CE hardware
issues the XFER_BUSY interrupt when the accumulation is complete.
Meter Equations
Compute Engine (CE) firmware and hardware for residential meter configurations implement the equations listed in
Table 3. The register EQU (located in the I/O RAM) specifies the equation to be used based on the number of phases
used for metering.
EQU
Description
0
1 element, 2W 1φ with neutral current sense
and tamper detection (VA connected to VB)
1 1 element, 3W 1φ
2 2 element, 4W 2φ
Watt & VAR Formula
Element 0
Element 1
VA IA
VA IB
VA(IA-IB)/2
VA IA
N/A
VB IB
Table 3: Meter Equations.
Page: 14 of 107
Rev 2