A/D Converter Operation Mode - NEC mPD780024AS Series Preliminary User's Manual

CHAPTER 11 8-BIT A/D CONVERTER ( µ PD780024AS SUBSERIES)

11.4.3 A/D converter operation mode

Select one analog input channel from among ANI0 to ANI3 by the analog input channel specification register 0
(ADS0) to start A/D conversion.
A/D conversion can be started in either of the following two ways.
• Hardware start: Conversion is started by trigger input (rising edge, falling edge, or both rising and falling edges
specified).
• Software start: Conversion is started by specifying the A/D converter mode register 0 (ADM0).
The A/D conversion result is stored in the A/D conversion result register 0 (ADCR0), and the interrupt request signal
(INTAD0) is simultaneously generated.
(1) A/D conversion by hardware start
When bit 6 (TRG0) and bit 7 (ADCS0) of the A/D converter mode register 0 (ADM0) are set to 1, the A/D conversion
standby state is set. When the external trigger signal (ADTRG) is input, A/D conversion of the voltage applied
to the analog input pins specified by the analog input channel specification register 0 (ADS0) starts.
Upon the end of the A/D conversion, the conversion result is stored in the A/D conversion result register 0
(ADCR0), and the interrupt request signal (INTAD0) is generated. After one A/D conversion operation is started
and ended, the next conversion operation is not started until a new external trigger signal is input.
If ADS0 is rewritten during A/D conversion, the converter suspends A/D conversion 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 ADS0 is rewritten during A/D conversion waiting, A/D conversion starts when the following
external trigger input signal is input.
If data with ADCS0 set to 0 is written to ADM0 during A/D conversion, the A/D conversion operation stops
immediately.
Caution When P03/INTP3/ADTRG is used as the external trigger input (ADTRG), specify the valid edge
by bits 1 and 2 (EGA00, EGA01) of the A/D converter mode register 0 (ADM0) and set the
interrupt mask flag (PMK3) to 1.
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Preliminary User's Manual U16035EJ1V0UM