If ADATE in ADCSRA is written to one, the value of these bits selects
which source will trigger an ADC conversion. If ADATE is cleared, the ADTS[2:0]
settings will have no effect. A conversion will be triggered by the rising edge
of the selected Interrupt Flag. Note that switching from a trigger source that
is cleared to a trigger source that is set, will generate a positive edge on the
trigger signal. If ADEN in ADCSRA is set, this will start a conversion.
Switching to Free Running mode (ADTS[2:0]=0) will not cause a trigger event,
even if the ADC Interrupt Flag is set.
Table 19-5. ADC Auto Trigger Source
Selection| ADTS[2:0] | Trigger Source |
|---|
| 000 | Free Running mode |
| 001 | Analog Comparator |
| 010 | External Interrupt Request 0 |
| 011 | Timer/Counter 0 Compare Match A |
| 100 | Timer/Counter 0 Overflow |
| 101 | Timer/Counter 0 Compare Match B |
| 110 | Pin Change Interrupt 0 Request |
| 111 | Timer/Counter 0 Capture Event |
