71M6531D Datasheet, PDF (54/115 Pages) Teridian Semiconductor Corporation – Energy Meter IC

Data Sheet 71M6531D/F-71M6532D/F
FDS 6531/6532 005
2.2 System Timing Summary
Figure 19 summarizes the timing relationships between the input MUX states, the CE_BUSY signal and
the two serial output streams. In this example, MUX_DIV=4 and FIR_LEN=2 (384 CE cycles, 3 CK32
cycles per conversion), resulting in 13 CK32 cycles per multiplexer frame. Generally, the duration of each
MUX frame is:
• 1 + MUX_DIV * 1, if FIR_LEN=0 (138 CE cycles)
• 1 + MUX_DIV * 2, if FIR_LEN=1 (288 CE cycles)
• 1 + MUX_DIV * 3, if FIR_LEN=2 (384 CE cycles).
An ADC conversion will always consume an integer number of CK32 clocks. Following this is a single
CK32 cycle where the bandgap voltage is allowed to recover from the change in CROSS.
ADC TIMING
ADC MUX Frame
MUX_DIV=4 (4 conversions) is shown
Settle
CK32
150
MUX_SYNC
MUX STATE S
0
1
2
3
S
ADC EXECUTION
CE TIMING
0
CE_EXECUTION
CE_BUSY
ADC0
ADC1
450
900
CK COUNT = CE_CYCLES + floor((CE_CYCLES + 2) / 5)
ADC2
1350
ADC3
1800
MAX CK COUNT
XFER_BUSY
INITIATED BY A CE OPCODE AT END OF SUMMATION INTERVAL
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 (PRE_SAMPS * SUM_CYCLES) CODE PASSES.
Figure 19: Timing Relationship between ADC MUX, Compute Engine
Each CE program pass begins when the ADC0 conversion (for IA) begins. Depending on the length of
the CE program, it may continue running until the end of the last conversion (ADC3). 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 RAM when the conversion is complete. The CE code is written
to tolerate sudden changes in ADC data. The exact clock count when each ADC value is loaded into
RAM is shown in Figure 19.
Figure 20 shows that the serial data stream, RTM, begins transmitting at the beginning of state S. RTM,
consisting of 140 CK cycles, will always finish before the next code pass starts.
CK32
MUX_SYNC
CKTEST
TMUXOUT/RTM
FLAG
RTM DATA 0 (32 bits)
RTM DATA 1 (32 bits)
RTM DATA 2 (32 bits)
RTM DATA 3 (32 bits)
0 1 _{30 31}
FLAG
0 1 _{30 31}
FLAG
0 1 30 ₃₁
FLAG
0 1 30 31
Figure 20: RTM Output Format
2.3 Battery Modes
Shortly after system power (V3P3SYS) is applied, the part will be in MISSION mode. MISSION mode
means that the part is operating with system power and that the internal PLL is stable. This mode is the
normal operation mode where the part is capable of measuring energy.
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