Operation; Single Mode; Scan Mode - Renesas H8S Series Hardware Manual
16-bit single-chip microcomputer
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19.4
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 in ADCSR to 0 to halt A/D
conversion. The ADST bit can be set at the same time the operating mode or analog input channel
is changed.
19.4.1
Single Mode
In single mode, A/D conversion is to be 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 wait state.
19.4.2
Scan Mode
In scan mode, A/D conversion is to be performed sequentially on the specified channels (max.
four channels). Operations are as follows.
1. When the ADST bit in ADCSR is set to 1 by software or an external trigger input, A/D
conversion starts on the first channel in the group (AN0 when the CH2 bit in ADCSR is 0, or
AN4 when the CH2 bit in ADCSR is 1).
2. When A/D conversion for each channel is completed, the result is sequentially transferred to
the A/D data register corresponding to each channel.
3. When conversion of all the selected channels is completed, the ADF bit in ADCSR is set to 1.
If the ADIE bit is set to 1 at this time, an ADI interrupt is requested after A/D conversion
ends. Conversion from the first channel in the group starts again.
4. The ADST bit is not automatically cleared to 0 so steps [2] and [3] are repeated as long as the
ADST bit remains set to 1. When the ADST bit is cleared to 0, A/D conversion stops.
Section 19 A/D Converter
Rev. 3.00 Jul. 14, 2005 Page 723 of 986
REJ09B0098-0300
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