SH7763 Datasheet, PDF (1732/2026 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC Engine Family SH-4A Series

Section 38 A/D Converter
38.4.3 Scan Mode (MDS1 = 1, MDS0 = 1)
In scan mode, A/D conversion is continuously repeated for the selected channels until the ADST
bit (bit 13) is cleared to 0. The A/D conversion results are transferred for storage to the ADDR that
corresponds to the channel. This mode is suitable for systems that continuously monitor analog
inputs to multiple channels (or a single channel). A/D conversion starts with the first channel
(AN0) when the ADST bit of the A/D control/status register (ADCSR) is set to 1 by software.
When multiple channels are selected, after A/D conversion for channel n ends, A/D conversion for
channel (n + 1) starts immediately.
A/D conversion is continuously repeated for the selected channels until the ADST bit is cleared to
0. The conversion results are transferred for storage to the ADDR that corresponds to the channel.
When setting the A/D control/status register (ADCSR) or switching the analog input channel
during A/D conversion, first clear the ADST bit to 0 to halt A/D conversion in order to avoid
malfunction. After the change has been made, setting the ADST bit to 1 selects the first channel
and A/D conversion is resumed.
Typical operations when three channels (AN0 to AN2) are selected in scan mode are described
below. Figure 38.4 shows a timing diagram for this example.
1. Select scan mode as the operating mode (MDS[1:0] = 11) and AN0 to AN2 as the input
channels (CH[2:0] = 010). Then start A/D conversion (ADST = 1).
2. A/D conversion of the first channel (AN0) starts. When A/D conversion ends, the result is
transferred into ADDRA. Next, the second channel (AN1) is selected automatically and A/D
conversion starts.
3. A/D conversion proceeds in the same way up to the third channel (AN2).
4. When A/D conversion of all selected channels (AN0 to AN2) is completed, the ADF bit is set
to 1, the first channel (AN0) is selected again, and A/D conversion is consecutively performed.
(In multi mode, A/D conversion ends when the selected channels have been cycled through.
However, in scan mode, after the selected channels have been cycled through, A/D conversion
starts again from the first channel and is consecutively repeated.)
If the ADIE bit is set to 1 at this time, an ADI interrupt is generated after A/D conversion ends.
5. While the ADST bit is set to 1, steps 2 to 4 above are repeated.
When the ADST bit is cleared to 0, A/D conversion stops. After that, if the ADST bit is set to
1, A/D conversion starts again from the first channel (AN0).
Rev. 1.00 Oct. 01, 2007 Page 1666 of 1956
REJ09B0256-0100