SH7727 Datasheet, PDF (941/1109 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH RISC engine Family/SH7700 Series

Section 28 A/D Converter
28.4.2 Multi Mode (MULTI = 1, SCN = 0)
Multi mode should be selected when performing multi channel A/D conversions on one or more
channels including channel 1. When the ADST bit is set to 1 by software or external trigger input,
A/D conversion starts on the first channel in the group (AN2 when CH2 = 0, and AN4 when CH2
= 1). When two or more channels are selected, after conversion of the first channel (AN2 or AN4)
ends, conversion of the second channel (AN3 or AN5) starts immediately. Finally, all of the
specified channels are converted in a loop. The conversion results are transferred for storage into
the A/D data registers corresponding to the channels.
When the mode or analog input channel selection must be changed during A/D conversion, to
prevent incorrect operation, first clear the ADST bit to 0 in ADCSR 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 in group 1 (AN4 to AN6) are selected in multi mode are
described next. Figure 28.4 shows a timing diagram for this example.
1. Multi mode is selected (MULTI = 1), channel group 1 is selected (CH2 = 1), analog input
channels AN4 to AN6 are selected (CH1 = 1, CH0 = 0), and A/D conversion is started (ADST
= 1).
2. When A/D conversion of the first channel (AN4) is completed, the result is transferred into
ADDRA. Next, conversion of the second channel (AN5) starts automatically.
3. Conversion proceeds in the same way through the third channel (AN6).
4. When conversion of all selected channels (AN4 to AN6) is completed, the ADF flag is set to 1
and ADST bit is cleared to 0. If the ADIE bit is set to 1, an ADI interrupt is requested after
A/D conversion.
Rev. 5.00 Dec 12, 2005 page 869 of 1034
REJ09B0254-0500