chap11.asm

Motorola 6808嵌入式接口设计开发原程序

; Chapter 11 6808 assembly language programs
; Jonathan W. Valvano
; This software accompanies the book,
; Real Time Embedded Systems published by Brooks Cole
;

;  Program 11.16. Assembly software to sample data using the A/D (fixed channel).
; MC68HC08AZ32
; Analog signal connected to PTB1
;ADSCR Register ($0038)
;  7  COCO =0 on a write ADSCR,
;          =1 on A/D done
;  6  AIEN =0    no interrupts
;  5  ADCO =0   single conversion 
; 4-0 CH4-0 =0001 Mux addr PTB1
Init lda #$70   ;divide by 8
     sta ADCLK  ;internal
     rts           ;E clk timing
Samp lda  #1
     sta  ADSCR ;Start A/D
Loop brclr 7,ADSCR,Loop  
     lda  ADR  ;result
     rts

;  Program 11.17. Assembly software to sample data using the A/D (variable channel).
; MC68HC08AZ32
; Analog signal connected to PTB0-7
;ADSCR Register ($0038)
;  7  COCO =0 on a write ADSCR,
;          =1 on A/D done
;  6  AIEN =0    no interrupts
;  5  ADCO =0   single conversion 
; 4-0 CH4-0  Mux addr PTB0-7
Init lda #$70   ;divide by 8
     sta ADCLK  ;internal
     rts           ;E clk timing
;Reg A has channel 0 to 7
A2D  sta  ADSCR ;Start A/D
Loop brclr 7,ADSCR,Loop  
     lda  ADR  ;result
     rts