71M6511 Datasheet, PDF (47/95 Pages) Teridian Semiconductor Corporation – Single-Phase Energy Meter IC

71M6511/71M6511H
Single-Phase Energy Meter IC
DATA SHEET
AUGUST 2007
System Timing Summary
Figure 13 summarizes the timing relationships between the input MUX states, the CE_BUSY signal, and the two serial output
streams. In this example, MUX_DIV = 1 (four mux states) and FIR_LEN = 1 (3 CK32 cycles). Since FIR filter conversions
require two or three CK32 cycles, the duration of each MUX cycle is 1 + 2 * states defined by MUX_DIV if FIR_LEN = 0, and 1
+ 3 * states defined by MUX_DIV if FIR_LEN = 1. Followed by the conversions is a single CK32 cycle.
Each CE program pass begins when MUX_SYNC falls. Depending on the length of the CE program, it may continue running
until the end of the ADC5 conversion. CE opcodes are constructed to ensure that all CE code passes consume exactly the
same number of cycles. The result of each ADC conversion is inserted into the CE DRAM when the conversion is complete.
The CE code is designed to tolerate sudden changes in ADC data. The exact CK count when each ADC value is loaded into
DRAM is shown in Figure 13.
Figure 13 also shows that the two serial data streams, RTM and SSI, begin transmitting at the beginning of MUX_SYNC. RTM,
consisting of 140 CK cycles, will always finish before the next code pass starts. The SSI port begins transmitting at the same
time as RTM, but may significantly overrun the next code pass if a large block of data is required. Neither the CE nor the SSI
port will be affected by this overlap.
ADC, CE and SERIAL TIMING
ADC TIMING
ADC MUX Frame
MUX_DIV Conversions (MUX_DIV=4 is shown)
CK32
150
MUX_SYNC
MUX STATE S
0
1
2
ADC EXECUTION
CE TIMING
0
CE_EXECUTION
CE_BUSY
ADC0
ADC1
450
900
CK COUNT = CE_CYCLES + floor((CE_CYCLES + 2) / 5)
ADC2
1350
XFER_BUSY
RTM and SSI TIMING
INITIATED BY A CE OPCODE AT END OF SUM INTERVAL
RTM
SSI
Settle
3
S
ADC3
1800
MAX CK COUNT
140
LAST SSI TRANSFER
NOTES:
1. ALL DIMENSIONS ARE 5MHZ CK COUNTS.
2. THE PRECISE FREQUENCY OF CK IS 150*CRYSTAL FREQUENCY = 4.9152MHz.
3. XFER_BUSY OCCURS ONCE EVERY (PRESAMPS * SUM_CYCLES) CODE PASSES.
BEGIN SSI TRANSFER
Figure 13: Timing Relationship between ADC MUX, CE, and Serial Transfers
Figure 14, Figure 15, and Figure 16 show the RTM and SSI timing, respectively.
Page: 47 of 95
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