71M6545 Datasheet, PDF (107/134 Pages) Maxim Integrated Products – Four-Quadrant Metering, Phase Metrology Processors Flash/RAM Size

PDS_6545_009
Data Sheet 71M6545/H
Other transfer variables include those available for frequency and phase measurement, and those reflecting
the count of the zero-crossings of the mains voltage and the battery voltage. These transfer variables are
listed in Table 74.
MAINEDGE_X reflects the number of half-cycles accounted for in the last accumulated interval for the AC
signal of the phase specified in the FREQSEL[1 :0] field of the CECONFIG register (CE RAM 0x20[7:6]) .
MAINEDGE_X is useful for implementing a real-time clock based on the input AC signal.
Table 74: Other Transfer Variables
CE
Address
Name
Description
0x82
0x83
0x94
0x95
FREQ_X
MAINEDGE_X
PH_AtoB_X
PH_AtoC_X
Fundamental frequency:
LSB
≡
2184Hz
2³²
≈ 0.509 ⋅10^−6 Hz(for CT)
LSB
≡
2520Hz
2³²
≈
0.587 ⋅10^−6 Hz(for
Shunt)
The number of edge crossings of the selected voltage in the previous
accumulation interval. Edge crossings are either direction and are
de-bounced.
Voltage phase lag. The selection of the reference phase is based on
FREQSEL[1:0] in the CECONFIG register:
If FREQSEL[1:0] selects phase A: Phase lag from A to B.
If FREQSEL[1:0] selects phase B: Phase lag from B to C.
If FREQSEL[1:0] selects phase C: Phase lag from C to A.
Angle in degrees is (0 to 360): PH_AtoB_X * 360/N_ACC + 2.4*15/13 (for CT)
Angle in degrees is (0 to 360): PH_AtoB_X * 360/N_ACC + 2.4 (for Shunt)
If FREQSEL[1:0] selects phase A: Phase lag from A to C.
If FREQSEL[1:0] selects phase B: Phase lag from B to A.
If FREQSEL[1:0] selects phase C: Phase lag from C to B.
Angle in degrees is (0 to 360): PH_AtoC_X * 360/N_ACC + 4.8*15/13 (for CT)
Angle in degrees is (0 to 360): PH_AtoC_X * 360/N_ACC + 4.8*15/13 (for Shunt)
Phase angle measurement accuracy can be increased by writing values > 1 into V_ANG_CNT (see
Table 69).
5.4.9 Pulse Generation
Table 75 describes the CE pulse generation parameters.
The combination of the CECONFIG PULSE_SLOW (CE RAM 0x20[0]) and PULSE_FAST (CE RAM 0x20[1])
bits controls the speed of the pulse rate. The default values of 0 and 0 maintain the original pulse rate
given by the Kh equation.
WRATE (CE RAM 0x21) controls the number of pulses that are generated per measured Wh and VARh
quantities. The lower WRATE is the slower the pulse rate for measured energy quantity. The metering
constant Kh is derived from WRATE as the amount of energy measured for each pulse. That is, if Kh =
1Wh/pulse, a power applied to the meter of 120 V and 30 A results in one pulse per second. If the load is
240 V at 150 A, ten pulses per second are generated.
Control is transferred to the MPU for pulse generation if EXT_PULSE = 1 (CE RAM 0x20[5]). In this case,
the pulse rate is determined by APULSEW and APULSER (CE RAM 0x44 and 0x48). The MPU has to load
the source for pulse generation in APULSEW and APULSER to generate pulses. Irrespective of the
EXT_PULSE status, the output pulse rate controlled by APULSEW and APULSER is implemented by the CE
only. By setting EXT_PULSE = 1, the MPU is providing the source for pulse generation. If EXT_PULSE is 0,
W0SUM_X and VAR0SUM_X are the default pulse generation sources. In this case, creep cannot be
controlled since it is an MPU function.
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