User Manual

Functional Description (Continued)

SAMPLE PROGRAM FOR

FIGURE 14

ADC0801-MC6800 CPU INTERFACE

0010 DF 36 DATAIN STX TEMP2 ; Save contents of X

0012 CE 00 2C LDX #$002C ; Upon IRQ

low CPU

0015 FF FF F8 STX $FFF8 ; jumps to 002C

0018 B7 50 00 STAA $5000 ; Start ADC0801

001B 0E CLI

001C 3E CONVRT WAI ; Wait for interrupt

001D DE 34 LDX TEMP1

001F 8C 02 0F CPX #$020F ; Is final data stored?

0022 27 14 BEQ ENDP

0024 B7 50 00 STAA $5000 ; Restarts ADC0801

0027 08 INX

0028 DF 34 STX TEMP1

002A 20 F0 BRA CONVRT

002C DE 34 INTRPT LDX TEMP1

002E B6 50 00 LDAA $5000 ; Read data

0031 A7 00 STAA X ; Store it at X

0033 3B RTI

0034 02 00 TEMP1 FDB $0200 ; Starting address for

; data storage

0036 00 00 TEMP2 FDB $0000

0038 CE 02 00 ENDP LDX #$0200 ; Reinitialize TEMP1

003B DF 34 STX TEMP1

003D DE 36 LDX TEMP2

003F 39 RTS ; Return from subroutine

; To user’s program

Note 1: In order for the microprocessor to service subroutines and interrupts, the stack pointer must be dimensioned in the user’s program.

TL/H/5671–25

FIGURE 15. ADC0801– MC6820 PIA Interface