32.5 Computation Operation

The ADC module hardware is equipped with post conversion computation features. These features provide data post-processing functions that can be operated on the ADC conversion result, including digital filtering/averaging and threshold comparison functions.

Figure 32-11. Computational Features Simplified Block Diagram

The operation of the ADC computational features is controlled by the ADMD bits.

The module can be operated in one of five modes:

Basic: This is a legacy mode. In this mode, ADC conversion occurs on single (ADDSEN = 0) or double (ADDSEN = 1) samples. ADIF is set after each conversion is complete.
Accumulate: With each trigger, the ADC conversion result is added to the accumulator and ADCNT increments. ADIF is set after each conversion. ADTIF is set according to the calculation mode.
Average: With each trigger, the ADC conversion result is added to the accumulator. When the ADRPT number of samples have been accumulated, a threshold test is performed. Upon the next trigger, the accumulator is cleared. For the subsequent tests, additional ADRPT samples are required to be accumulated.
Burst Average: At the trigger, the accumulator is cleared. The ADC conversion results are then collected repetitively until ADRPT samples are accumulated and finally the threshold is tested.
Low-Pass Filter (LPF): With each trigger, the ADC conversion result is sent through a filter. When ADRPT samples have occurred, a threshold test is performed. Every trigger after that the ADC conversion result is sent through the filter and another threshold test is performed.

The five modes are summarized in the following table.

Table 32-4. Computation Modes
		Register Clear Event	Value after Cycle⁽²⁾ Completion		Threshold Operations			Value at ADTIF Interrupt
Mode	ADMD	ADACC and ADCNT	ADACC⁽¹⁾	ADCNT	Retrigger	Threshold Test	Interrupt	ADAOV	ADFLTR	ADCNT
Basic	0	ADACLR = `1`	Unchanged	Unchanged	No	Every Sample	If threshold=true	N/A	N/A	count
Accumulate	1	ADACLR = `1`	S1 + ADACC or (S2-S1) + ADACC	If (ADCNT=FF): ADCNT, otherwise: ADCNT+1	No	Every Sample	If threshold=true	ADACC Overflow	ADACC/2^ADCRS	count
Average	2	ADACLR = `1` or ADCNT ≥ ADRPT at ADGO or retrigger	S1 + ADACC or (S2-S1) + ADACC	If (ADCNT=FF): ADCNT, otherwise: ADCNT+1	No	If ADCNT ≥ ADRPT	If threshold=true	ADACC Overflow	ADACC/2^ADCRS	count
Burst Average	3	ADACLR = `1` or ADGO set or retrigger	Each repetition: same as Average End with sum of all samples	Each repetition: same as Average End with ADCNT=ADRPT	Repeat while ADCNT < ADRPT	If ADCNT ≥ ADRPT	If threshold=true	ADACC Overflow	ADACC/2^ADCRS	ADRPT
Low-pass Filter	4	ADACLR = `1`	S1 + ADACC-ADACC/ 2^ADCRS or (S2-S1) + ADACC-ADACC/2^ADCRS	If (ADCNT=FF): ADCNT, otherwise: ADCNT+1	No	If ADCNT ≥ ADRPT	If threshold=true	ADACC Overflow	Filtered Value	count
Note: S1 and S2 are abbreviations for Sample 1 and Sample 2, respectively. When ADDSEN = `0`, S1 = ADRES. When ADDSEN = `1`, S1 = ADPREV and S2 = ADRES. When ADDSEN = `0`, then Cycle means one conversion. When ADDSEN = `1` then Cycle means two conversions.