38.2.1 Class 2 Triggering

When a single Class 2 input is triggered, it is sampled and converted by the shared S&H using the sequence illustrated in Sample and Conversion Sequence for the Shared ADC Modules figure; see Sample and Conversion Sequence for Shared ADC Modules figure in the ADC Operation from Related Links. When multiple Class 2 inputs are triggered, it is important to understand the consequences of trigger timing. If a conversion is underway and another Class 2 trigger occurs, then the sample-hold-conversion for the new trigger is stalled until the in-process, sample-hold cycle is complete, as shown in the following figure.

When multiple inputs to the shared S&H are triggered simultaneously, the processing order is determined by their natural priority (the lowest numbered input has the highest priority). As an example, if AN1, AN2 and AN3 are triggered simultaneously, AN1 is sampled and converted first, followed by AN2 and finally, AN3. When using the independent Class 2 triggering on the shared S&H, the SAMC[9:0] bits (ADCCON2[25:16]) determine the sample time for all inputs while the appropriate TRGSRC[4:0] bits in the ADCTRGx Register (see ADCTRG1 register from Related Links) determine the trigger source for each input.