SAMPLE PROGRAM FOR ADC0844 — INS8039 INTERFACE

CONVERTING TWO RATIOMETRIC, DIFFERENTIAL SIGNALS (Continued)

0054

32 53

JB1

LOOP

;IF INTR = 1 GOTO LOOP

0056

81

MOVX

;IF INTR = 0 INPUT A/D DATA

0057

89 01

ORL

P1,&01H

;CLEAR THE A/D CHIP SELECT

0059

A0

MOV

;STORE THE A/D DATA

005A

83

RET

;RETURN TO MAIN PROGRAM

SAMPLE PROGRAM FOR ADC0848 — NSC800 INTERFACE

0008

NCONV

EQU

16

000F

DEL

EQU

15

;DELAY 50 µsec CONVERSION

001F

CS

EQU

1FH

;THE BOARD ADDRESS

3C00

ADDTA

EQU

003CH

;START OF RAM FOR A/D

;DATA

0000'

08 09 0A 0B

MUXDTA:

DB

08H,09H,0AH,0BH

;MUX DATA

0004'

0C 0D 0E 0F

DB

0CH,0DH,0EH,0FH

0008'

0E 1F

START:

LD

C,CS

000A'

06 16

LD

B,NCONV

000C'

21 0000'

LD

HL,MUXDTA

000F'

11 003C

LD

DE,ADDTA

0012'

ED A3

STCONV:

OUTI

;LOAD A/D’S MUX DATA

;AND START A CONVERSION

0014'

EB

EX

DE,HL

;HL=RAM ADDRESS FOR THE

;A/D DATA

0015'

3E 0F

LD

A,DEL

0017'

3D

WAIT:

DEC

A

;WAIT 50 µsec FOR THE

0018'

C2 0013'

JP

NZ,WAIT

;CONVERSION TO FINISH

001B'

ED A2

INI

;STORE THE A/D’S DATA

;CONVERTED ALL INPUTS?

001D'

EB

EX

DE,HL

001E'

C2 000E'

JP

NZ,STCONV

;IF NOT GOTO STCONV

END

Note 14: This routine sequentially programs the MUX data latch in the signal-ended mode. For CH1-CH8 a conversion is started, then a 50 µs wait for the A/D to

complete a conversion and the data is stored at address ADDTA for CH1, ADDTA + 1 for CH2, etc.

I/O Interface to NSC800

DS005016-28

www.national.com

17