71M6542F MAXIM [Maxim Integrated Products], 71M6542F Datasheet - Page 125

• Manufacturer Part Number: 71M6542F
• Description: 0.1% Accuracy Over 2000:1 Current Range Energy Meter ICs
• Manufacturer: MAXIM [Maxim Integrated Products]

must be copied to CE data memory by the MPU before enabling the CE. Internal variables are used in
variables are outputs of the CE calculations. The corresponding MPU address for the most significant
byte is given by 0x0000 + 4 x CE_address and by 0x0003 + 4 x CE_address for the least significant byte.
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5.3
5.3.1 CE Program
The CE performs the precision computations necessary to accurately measure energy. These computations
include offset cancellation, phase compensation, product smoothing, product summation, frequency
detection, VAR calculation, sag detection and voltage phase measurement. All data computed by the CE
is dependent on the selected meter equation as given by EQU[2:0] (I/O RAM 0x2106[7:5]).
The CE program is supplied by Teridian as a data image that can be merged with the MPU operational
code for meter applications. Typically, the CE program provided with the demonstration code covers
most applications and does not need to be modified. Other variations of CE code are available from
Teridian. The descriptions provided in this section apply to the CE code revisions shown in
Please contact the local Teridian representative to obtain the appropriate CE code required for a specific
application.
5.3.2 CE Data Format
All CE words are 4 bytes. Unless specified otherwise, they are in 32-bit two’s complement format
(-1 = 0xFFFFFFFF). Calibration parameters are defined in flash memory (or external EEPROM) and
internal CE calculations. Input variables allow the MPU to control the behavior of the CE code. Output
5.3.3 Constants
Constants used in the CE Data Memory tables are:
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The system constants IMAX and VMAX are used by the MPU to convert internal digital quantities (as
used by the CE) to external, i.e., metering quantities. Their values are determined by the scaling of the
voltage and current sensors used in an actual meter. The LSB values used in this document relate digital
quantities at the CE or MPU interface to external meter input quantities. For example, if a SAG threshold
of 80 V rms is desired at the meter input, the digital value that should be programmed into SAG_THR (CE
RAM 0x24) would be 80 Vrms * SQRT(2)/SAG_THR
description of SAG_THR (see
Sampling Frequency: F
F
IMAX is the external rms current corresponding to 250 mV pk (176.8 mV rms) at the inputs IA and IB.
IMAX needs to be adjusted if the pre-amplifier is activated for the IAP-IAN inputs. For a 250 µΩ shunt
resistor, IMAX becomes 707 A (176.8 mV rms / 250 µΩ = 707.2 A rms).
VMAX is the external rms voltage corresponding to 250 mV pk at the VA and VB inputs.
N
0x2108[7:0]).
The duration of the accumulation interval for energy measurements is SUM_SAMPS[12:0] / F
X is a gain constant of the pulse generators. Its value is determined by PULSE_FAST and PULSE_SLOW
(see
Voltage LSB (for sag threshold) = VMAX * 7.879810
0
ACC
is the fundamental frequency of the mains phases.
CE Interface Description
Table
, the accumulation count for energy measurements is SUM_SAMPS[12:0] (I/O RAM 0x2107[4:0],
83).
71M6541D/F/G
71M6542F/G
Device
S
= 32768 Hz/13 = 2520.62 Hz.
Table
84).
Table 77. Standard CE Codes
CE41A01 (Eq. 0 or 1)
CE41A01 (Eq. 0 or 1)
CE41A04 (Eq. 2)
Local Sensors
LSB
, where SAG_THR
-9
V.
71M6541D/F/G and 71M6542F/G Data Sheet
Remote Sensor
CE41B016601
CE41B016201
(Eq. 0, 1 or 2)
LSB
is the LSB value in the
Table
S
.
77.