71M6511/71M6511H
Single-Phase Energy Meter IC
DATA SHEET
AUGUST 2007
Real-Time Monitor
The CE contains a Real Time Monitor (RTM), which can be programmed to monitor four selectable CE RAM locations at full
sample rate. The four monitored locations are serially output to the TMUXOUT pin via the digital output multiplexer at the
beginning of each CE code pass (see the Test Ports Section for details)
CE Functional Overview
The ADC processes one sample per channel per multiplexer cycle. Figure 4 shows the timing of the samples taken during one
multiplexer cycle.
The number of samples processed during one accumulation cycle is controlled by the I/O RAM registers
PRE_SAMPS
(0x2001[7:6]) and
SUM_CYCLES
(0x2001[5:0]). The integration time for each energy output is
PRE_SAMPS
*
SUM_CYCLES
/ 2520.6, where 2520.6 is the sample rate [Hz] (for
MUX_DIV
= 1)
For example,
PRE_SAMPS
= 42 and
SUM_CYCLES
= 50 will establish 2100 samples per accumulation cycle.
PRE_SAMPS
=
100 and
SUM_CYCLES
= 21 will result in the exact same accumulation cycle of 2100 samples or 833ms. After an
accumulation cycle is completed, the XFER_BUSY interrupt signals to the MPU that accumulated data are available.
1/32768Hz =
30.518µs
IB
IA
VA
13/32768Hz = 397µs
per mux cycle
Figure 4: Samples in Multiplexer Cycle
The end of each multiplexer cycle is signaled to the MPU by the CE_BUSY interrupt. At the end of each multiplexer cycle,
status information, such as sag data and the digitized input signal, is available to the MPU.
833ms
20ms
XFER_BUSY
Interrupt to MPU
Figure 5: Accumulation Interval
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