SH7706 Datasheet, PDF (587/749 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH™ RISC engine Family/SH7700 Series

Section 19 A/D Converter (ADC)
19.6 Operation
The A/D converter operates by successive approximations with 10-bit resolution. It has two
operating modes: single mode and scan mode.
19.6.1 Single Mode (MULTI = 0)
Single mode should be selected when only one A/D conversion on one channel is required. A/D
conversion starts when the ADST bit in ADCSR is set to 1 by software, or by external trigger
input. The ADST bit remains set to 1 during A/D conversion and is automatically cleared to 0
when conversion ends.
When conversion ends the ADF bit is set to 1. If the ADIE bit is also set to 1, an ADI interrupt is
requested at this time. To clear the ADF flag to 0, first read ADCSR, then write 0 in ADF.
When the mode or analog input channel must be switched 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 to start A/D conversion again. The ADST bit can be
set at the same time as the mode or channel is changed.
Typical operations when channel 1 (AN1) is selected in single mode are described next.
Figure 19.5 shows a timing diagram for this example.
1. Single mode is selected (MULTI = 0), input channel AN1 is selected (CH2 = CH1 = 0, CH0 =
1), the A/D interrupt is enabled (ADIE = 1), and A/D conversion is started (ADST = 1).
2. When A/D conversion is completed, the result is transferred into ADDRB. At the same time
the ADF flag is set to 1, the ADST bit is cleared to 0, and the A/D converter becomes idle.
3. Since ADF = 1 and ADIE = 1, an ADI interrupt is requested.
4. The A/D interrupt processing routine starts.
5. The routine reads ADCSR, then writes 0 in the ADF flag.
6. The routine reads and processes the conversion result (ADDRB = 0).
7. Execution of the A/D interrupt processing routine ends. Then, when the ADST bit is set to 1,
A/D conversion starts to execute 2 to 7 above.
Rev. 5.00 May 29, 2006 page 539 of 698
REJ09B0146-0500