Datasheet

Section 17 A/D Converter
Rev. 3.00 Sep. 28, 2009 Page 493 of 710
REJ09B0384-0300
17.4 Operation
The A/D converter operates by successive approximation with 10-bit resolution. It has two
operating modes: single mode and scan mode. When changing the operating mode or analog input
channel, to prevent incorrect operation, first clear the ADST bit to 0 in ADCSR to halt A/D
conversion. The ADST bit can be set to 1 at the same time as the operating mode or analog input
channel is changed.
17.4.1 Single Mode
In single mode, A/D conversion is performed only once on the specified single channel.
Operations are as follows.
1. A/D conversion on the specified channel is started when the ADST bit in ADCSR is set to 1,
by software or an external trigger input.
2. When A/D conversion is completed, the result is transferred to the A/D data register
corresponding to the channel.
3. On completion of A/D conversion, the ADF bit in ADCSR is set to 1. If the ADIE bit is set to
1 at this time, an ADI interrupt request is generated.
4. The ADST bit remains set to 1 during A/D conversion. When conversion ends, the ADST bit
is automatically cleared to 0, and the A/D converter enters the idle state. If the ADST bit is
cleared during A/D conversion, the A/D converter stops conversion and enters the idle state.