SH7041A datasheet(614/923 Pages) RENESAS

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16.4

Operation

The mid-speed converter operates using the continuous comparison method and is equipped with

10-bit resolution. Operations for the single and scan modes are explained below.

16.4.1

Single Mode (SCAN=0)

The single mode is selected when executing A/D conversion for one channel only. A/D conversion

is initiated when the ADST bit of the A/D control/status register is set to 1 by the software or

external trigger input. The ADST bit is held to 1 during the A/D conversion and is automatically

cleared to 0 upon completion.

When conversion is complete, the ADF bit of ADCSR is set to 1. At this time, if the ADIE bit of

ADCSR is 1, ADI interrupt request occurs.

The ADF bit can be cleared by writing 0 after reading ADF=1.

To switch modes or analog input channels during A/D conversion, clear the ADST bit to 0 and

stop A/D conversion to avoid malfunction. After switching (mode/channel change and ADST bit

setting can be made at the same time), set the ADST bit to 1 to restart A/D conversion.

An example of operation when channel 1 (AN1) is selected in the single mode is shown in figure

16.3 (the bit specification in the example is the ADCSR0 register).

Set operation mode to single mode (SCAN=0), input channel to AN1 (CH1=0, CH0=1) and

A/D interrupt request to enable (ADIE) then start A/D conversion (ADST=1).

2. When A/D conversion is complete, A/D conversion result is transferred to ADDRB0. At the

same time, ADF=1 will become ADF=0 and the mid-speed converter will standby for

conversion.

Since ADF=1 and ADIE=1, ADI interrupt request will occur.

4. The A/D interrupt process routine will start.

After reading ADF=1, write 0 to ADF.

Read the A/D conversion result (ADDRB0) and process.

End A/D interrupt process routine execution. When ADST bit is set to 1, A/D conversion

starts, following steps (2) to (7) above.

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