71M6511/71M6511H
Single-Phase Energy Meter IC
DATA SHEET
AUGUST 2007
XFER_BUSY interrupt. After these first two cycles, CHOP_EN returns to 11 (automatic toggle). The value of CHOP_EN, when
set after the XFER_BUSY interrupt, is in force for the entire following multiplexer cycle.
When using this sequence, the alternate multiplexer cycle is toggled between positive and reversed connection resulting in
accurate temperature measurement.
An example for proper application of the CHOP_EN bits can be found in the Demo Code shipped with the 6511 and 6511
Demo Kits. Firmware implementations should closely follow this example.
Accumulation Interval m
Accumulation Interval m+1
Accumulation Interval m+2
alt. MUX
cycle
MUX
MUX
MUX
MUX
MUX
alt. MUX
cycle
alt. MUX
cycle
MUX
MUX
MUX
MUX
cycle 2 cycle 3
cycle n
cycle n
cycle n
cycle 2 cycle 3
cycle 2
cycle 3
Chop Polarity
re-
re-
re-
re-
re-
Positive
Positive
Positive Positive
Positive
Positive Positive
versed
versed
versed
versed
versed
CE_BUSY interrupt
XFER_BUSY interrupt
MUX_ALT
CHOP_EN
01
11
(11)
(11)
(11)
10
11
(11)
(11)
(11)
01
11
(11)
(11)
(11)
Figure 23: Sequence with Alternate Multiplexer Cycles and Controlled Chopping
Internal/External Pulse Generation and Pulse Counting
The CE is the source for pulses. It can generate pulses directly based on the voltage and current inputs and the configured
pulse generation parameters. This is called “internal pulse generation”, and applies when the CE RAM register EXT_PULSE
(address 0x37) equals 0. Alternatively, the CE can be configured to generate pulses based on registers that are controlled by
the MPU (“external pulse generation”), i.e. when the register EXT_PULSE equals 15. In the case of external pulse generation,
the MPU writes values to the CE registers APULSEW (0x26) and APULSER (0x27).
The pulse rate, usually inversely expressed as “Kh” (and measured in Wh per pulse), is determined by the CE RAM registers
WRATE, PULSE_SLOW, PULSE_FAST, In_8, as well as by the sensor scaling VMAX and IMAX per the equation:
VMAX ⋅ IMAX ⋅47.1132
In_8⋅WRATE ⋅ NACC ⋅ X
Kh =
[Wh/ pulse]
where
In_8 is the gain factor (1 or 8) controlled by the CE variable In_SHUNT,
X is the pulse gain factor controlled by the CE variables PULSE_SLOW and PULSE_FAST
NACC is the accumulation count (PRE_SAMPS * SUM_CYCLES)
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