CHAPTER 12 A/D CONVERTER
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User’s Manual U11302EJ4V0UM
12.4.3 A/D converter operating mode
Select one analog input channel from among ANI0 to ANI7 using the A/D converter input select register (ADIS)
and A/D converter mode register (ADM) and start A/D conversion.
A/D conversion can be started in the following two ways.
•
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 the 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, A/D conversion starts on the
voltage applied to the analog input pins specified by bits 1 to 3 (ADM1 to ADM3) of ADM.
At the end of 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 12-6. A/D Conversion by Hardware Start
Remark
n
= 0, 1, ... , 7
m = 0, 1, ... , 7
ANIn
INTAD
ADCR
A/D conversion
INTP3
Standby
state
ANIn
ANIn
Standby
state
ANIn
Standby
state
ANIm
ANIm
ANIm
ANIn
ANIn
ANIm
ANIm
ADM rewrite
CS = 1, TRG = 1
ADM rewrite
CS = 1, TRG = 1
Содержание mPD780204
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