276
CHAPTER 14 A/D CONVERTER
14.4.3 A/D converter operating mode
Select one analog input channel from ANI0 to ANI7 with A/D converter input select register (ADIS) and A/D
converter mode register (ADM), and start A/D conversion.
The following two ways are available to start A/D conversion.
• Hardware start: Conversion is started by trigger input (INTP3).
• Software start: Conversion is started by setting ADM.
The A/D conversion result is stored in the A/D conversion result register (ADCR) and the interrupt request signal
(INTAD) is simultaneously generated.
(1) A/D conversion by hardware start
When bit 6 (TRG) and bit 7 (CS) of A/D converter mode register (ADM) are set to 1, the A/D conversion standby
state is set. When the external trigger signal (INTP3) is input, the A/D conversion starts on the voltage applied
to the analog input pins specified with bits 1 to 3 (ADM1 to ADM3) of ADM.
Upon termination of the A/D conversion, the conversion result is stored in the A/D conversion result register
(ADCR) and the interrupt request signal (INTAD) is generated. After one A/D conversion operation is started
and terminated, another operation is not started until a new external trigger signal is input.
If data with CS set to 1 is written to ADM again during A/D conversion, the converter suspends its A/D
conversion operation and waits for a new external trigger signal to be input. When the external trigger input
signal is reinput, A/D conversion is carried out from the beginning.
If data with CS set to 0 is written to ADM during A/D conversion, the A/D conversion operation stops
immediately.
Figure 14-8. A/D Conversion by Hardware Start
Remarks 1. n = 0, 1, ... , 7
2. m = 0, 1, ... , 7
ADM Rewrite
CS=1, TRG=1
Standby
State ANIn
INTP3
A/D Conversion
ADCR
INTAD
ANIn ANIn ANIn ANIm ANIm
ANIn ANIn
Standby
State
Standby
State
ADM Rewrite
CS=1, TRG=1
ANIm ANIm ANIm