71M6533 Datasheet, PDF (96/132 Pages) Teridian Semiconductor Corporation – Energy Meter IC

71M6533/G/H and 71M6534/H Data Sheet
FDS_6533_6534_004
5.3.4 Environment
Before starting the CE using the CE_E bit, the MPU has to establish the proper environment for the CE by
implementing the following steps:
• Load the CE data into RAM.
• Establish the equation to be applied in EQU[2:0].
• Establish the accumulation period and number of samples in PRE_SAMPS[1:0] and SUM_CYCLES[5:0].
• Establish the number of cycles per ADC multiplexer frame (MUX_DIV[3:0]).
• Apply proper values to SLOTn_SEL[3:0] and SLOTn_ALTSEL[3:0].
• Set PLS_INTERVAL[7:0] to 81.
• Select the proper values for FIR_LEN[1:0] (1) and MUX_DIV[3:0] (6).
• Set CHOP_E[1:0] = 00.
• Initialize any MPU interrupts, such as CE_BUSY, XFER_BUSY, or a power failure detection interrupt.
When different CE codes are used, a different set of environment parameters needs to be established.
The exact values for these parameters are stated in the Application Notes and other documentation
accompanying the CE codes.
Operating CE codes with environment parameters deviating from the values specified will lead to
unpredictable results.
Typically, there are thirteen 32768 Hz cycles per ADC multiplexer frame (see Figure 19 in the System
Timing Summary section). This means that the product of the number of cycles per frame and the number
of conversions per frame must be 12 (allowing for one settling cycle). The default configuration is FIR_LEN
= 1 (two cycles per conversion) and MUX_DIV[3:0] = 6 (6 conversions per mux cycle).
During operation, CHOP_E[1:0] = 00 enables the automatic chopping mode and forces an alternate
multiplexer sequence at regular intervals. This enables accurate temperature measurement.
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