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Section 24 A/D Converter
R01UH0134EJ0400 Rev. 4.00 Page 1271 of 2108
Sep 24, 2014
SH7262 Group, SH7264 Group
24.4.2 Multi Mode
Multi mode should be selected when performing A/D conversion once on one or more channels.
In multi mode, A/D conversion is performed once for a maximum of eight specified analog input
channels, as follows:
1. A/D conversion starts from the analog input channel with the lowest number (e.g. AN0, AN1,
…, AN3) when the ADST bit in ADCSR is set to 1 by software, the multi-function timer pulse
unit 2, or external trigger input.
2. When A/D conversion is completed on each channel, the A/D conversion result is sequentially
transferred to the A/D data register corresponding to that channel.
3. After A/D conversion on all selected channels has completed, 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 that remains 1 during A/D conversion is automatically cleared to 0 when A/D
conversion is completed, and the A/D converter becomes idle. If the ADST bit is cleared to 0
during A/D conversion, A/D conversion is halted and the A/D converter becomes idle. The
ADF bit is cleared by reading ADF while ADF = 1, then writing 0 to the ADF bit.
A/D conversion is to be performed once on all the specified channels. The conversion results are
transferred for storage into the A/D data registers corresponding to the channels.
When the operating mode or analog input channel selection must be changed during A/D
conversion, to prevent incorrect operation, first clear the ADST bit to 0 to halt A/D conversion.
After making the necessary changes, set the ADST bit to 1. A/D conversion will start again from
the first channel in the group. The ADST bit can be set at the same time as the mode or channel
selection is changed.
Typical operations when three channels (AN0 to AN2) are selected in multi mode are described
next. Figure 24.3 shows a timing diagram for this example.
1. Multi mode is selected (MDS2 = 1, MDS1 = 0), analog input channels AN0 to AN2 are
selected (CH[2:0] = 010), and A/D conversion is started (ADST = 1).
2. A/D conversion of the first channel (AN0) starts. When A/D conversion is completed, the A/D
conversion result is transferred into ADDRA.
3. Next, the second channel (AN1) is selected automatically and A/D conversion starts.
4. Conversion proceeds in the same way through the third channel (AN2).
5. When conversion of all selected channels (AN0 to AN2) is completed, the ADF flag is set to 1
and the ADST bit cleared to 0.
6. If the ADIE bit is set to 1 at this time, an ADI interrupt is requested.