31.3.2.1 Starting a Conversion

Once the input channel is selected by writing to the MUXPOS register (ADCn.MUXPOS), a conversion is triggered by writing a '1' to the ADC Start Conversion bit (STCONV) in the Command register (ADCn.COMMAND). This bit is one as long as the conversion is in progress. In Single Conversion mode, STCONV is cleared by hardware when the conversion is completed.

If a different input channel is selected while a conversion is in progress, the ADC will finish the current conversion before changing the channel.

Depending on the accumulator setting, the conversion result is from a single sensing operation, or from a sequence of accumulated samples. Once the triggered operation is finished, the Result Ready flag (RESRDY) in the Interrupt Flag register (ADCn.INTFLAG) is set. The corresponding interrupt vector is executed if the Result Ready Interrupt Enable bit (RESRDY) in the Interrupt Control register (ADCn.INTCTRL) is one and the Global Interrupt Enable bit is one.

A single conversion can be started by writing a '1' to the STCONV bit in ADCn.COMMAND. The STCONV bit can be used to determine if a conversion is in progress. The STCONV bit will be set during a conversion and cleared once the conversion is complete.

The RESRDY interrupt flag in ADCn.INTFLAG will be set even if the specific interrupt is disabled, allowing software to check for finished conversion by polling the flag. A conversion can thus be triggered without causing an interrupt.

Alternatively, a conversion can be triggered by an event. This is enabled by writing a '1' to the Start Event Input bit (STARTEI) in the Event Control register (ADCn.EVCTRL). Any incoming event routed to the ADC through the Event System (EVSYS) will trigger an ADC conversion. This provides a method to start conversions at predictable intervals or at specific conditions.

The event trigger input is edge sensitive. When an event occurs, STCONV in ADCn.COMMAND is set. STCONV will be cleared when the conversion is complete.

In Free-Running mode, the first conversion is started by writing the STCONV bit to '1' in ADCn.COMMAND. A new conversion cycle is started immediately after the previous conversion cycle has completed. A conversion complete will set the RESRDY flag in ADCn.INTFLAGS.