UPD17708 datasheet(200/356 Pages) NEC

200 / 356 page

µPD17704, 17705, 17707, 17708, 17709

200

14.5 Using A/D Converter

14.5.1 Software mode

The software mode is convenient for comparing one compare voltage.

An example of a program in this mode is shown below.

Example To compare input voltage VADCIN of AD0 pin with compare voltage VADCREF (127.5/256 VDD), and

branch to AAA if VADCIN < VADCREF, or to BBB if VADCIN > VADCREF

ADCR7 FLG

0.0EH.3 ; Defines each bit of DBF as ADCR data setting flag

ADCR6 FLG

0.0EH.2

ADCR5 FLG

0.0EH.1

ADCR4 FLG

0.0EH.0

ADCR3 FLG

0.0EH.3

ADCR2 FLG

0.0EH.2

ADCR1 FLG

0.0EH.1

ADCR0 FLG

0.0EH.0

BANK15

INITFLG NOT P0DPLD3, NOT P0DPLD2, NOT P0DPLD1, P0DPLD0

; Disconnects pull-down resistor of P0D0 pin

BANK0

INITFLG NOT ADCCH2, NOT ADCCH1, ADCCH0

; Selects AD0 pin for A/D converter

CLR1

ADCMD

; Sets software mode

INITFLG ADCR7, NOT ADCR6, NOT ADCR5, NOT ADCR4

;

INITFLG NOT ADCR3, NOT ADCR2, NOT ADCR1, NOT ADCR0

;

PUT

ADCR, DBF

; Sets compare voltage VADCREF

NOP

; Waits for duration of three instructions

NOP

;

NOP

;

SKT1

ADCCMP

; Judges result of comparison

AAA

BBB

14.5.2 Hardware mode

Here is a program example:

Example To detect the value of analog input roltage VADCIN of AD0 pin.

BANK15

INITFLG NOT P0DPLD3, NOT P0DPLD2, NOT P0DPLD1, P0DPLD0 ; Disconnects pull-down resistor of P0D0 pin

BANK0

INITFLG NOT ADCCH2, NOT ADCCH1, ADCCH0

; Selects AD0 pin for A/D converter

SET1

ADCMD

; Sets hardware mode and starts conversion

LOOP:

SKT1

ADCSTT

; Detects end of A/D conversion

; Embedded macro instruction

;PEEK WR, .MF. ADCSTT SHR4 AND 0FH

;SKT1 WR,#.DF.ADCSTT AND 0FH

LOOP

; Conversion in progress

GET

DBF,ADCR

; Stores result of conversion to DBF

UPD17708 Datasheet(PDF) 200 Page - NEC

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