The AFEC Sleep mode maximizes power saving by automatically deactivating the AFE when it is not being used for conversions. Sleep mode is selected by setting AFEC_MR.SLEEP.
Sleep mode is managed by a conversion sequencer, which automatically processes the conversions of all channels at lowest power consumption.
This mode can be used when the minimum period of time between two successive trigger events is greater than the startup period of the AFEC. Refer to the AFE Characteristics in the section “Electrical Characteristics”.
When a start conversion request occurs, the AFE is automatically activated. As the analog cell requires a startup time, the logic waits during this lapse and starts the conversion on the enabled channels. When all conversions are complete, the AFE is deactivated until the next trigger. Triggers occurring during the sequence are not taken into account.
A fast wakeup mode is available in the AFEC_MR as a compromise between power-saving strategy and responsiveness. Setting the FWUP bit enables the Fast Wakeup mode. In Fast Wakeup mode, the AFE is not fully deactivated while no conversion is requested, thereby providing lower power savings but faster wakeup.
The conversion sequencer allows automatic processing with minimum processor intervention and optimized power consumption. Conversion sequences are performed periodically using a Timer/Counter output or the PWM event line.
The DMA can automatically process the periodic acquisition of several samples without processor intervention.
The sequence can be customized by programming the Channel Sequence registers AFEC_SEQ1R and AFEC_SEQ2R and setting AFEC_MR.USEQ. The user selects a specific order of channels and can program up to 12 conversions by sequence. The user may create a personal sequence by writing channel numbers in AFEC_SEQ1R and AFEC_SEQ2R. Channel numbers can be written in any order and repeated several times. Only enabled USCHx fields are converted. Thus, to program a 15-conversion sequence, the user disables AFEC_CHSR.CH15, thus disabling AFEC_SEQ2R.USCH15.