chap11.asm

摩托罗拉Mc6805利程

; Chapter 11 6805 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).
; MC68HC05B6
; Analog signal connected to D1
;ADSTAT Register ($0009)
;  7  COCO =0 on a write ADSTAT,
;          =1 on A/D done
;  6  0     internal clock
;  5  ADON =1   A/D enabled 
;  4        not implemented
; 3-0 CH3-0 =0001 Mux addr D1
Init rts    ; no ritual required
Samp lda #$21
     sta ADSTAT  ;Start A/D
Loop lda ADSTAT
     and #$80    ;check COCO
     beq Loop  
     lda ADDATA  ;result
     rts

;  Program 11.17. Assembly software to sample data using the A/D (variable channel).
; MC68HC05B6
; Analog signal to D0-7
;ADSTAT Register ($0009)
;  7  COCO =0 on a write ADSTAT,
;          =1 on A/D done
;  6  0     internal clock
;  5  ADON =1   A/D enabled 
;  4        not implemented
; 3-0 CH3-0 Mux addr D0-7
Init rts    ; no ritual required
;Reg A has channel 0 to 7
A2D  ora #$20
     sta ADSTAT  ;Start A/D
Loop lda ADSTAT
     and #$80    ;check COCO
     beq Loop  
     lda ADDATA  ;result
     rts