chap11.asm

Motorola 6812芯片开发的接口程序。

; Chapter 11 6812 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).
; MC68HC812A4/MC68HC912B32
; Analog signal connected to PAD1
;ATDCTL5 Register ($0065)
;   7  0     Not implemented
;   6  S8CM=0     4 conversions
;   5  SCAN =0    one set of 4 
;   4  MULT =0    single channel
;  3-0 CD-A =0001 Mux addr PAD1
Init ldaa  #$80    ;Turn on A/D
     staa  ATDCTL2 ;A/D power up
     rts           ;E clk timing
Samp ldaa  #1
     staa  ATDCTL5 ;Start A/D
Loop brclr ATDSTAT,$80,Loop  
     ldaa  ADR0H  ;first result
     rts

;  Program 11.17. Assembly software to sample data using the A/D (variable channel).
; MC68HC812A4/MC68HC912B32
; Analog signal connected to PAD7-0
;ATDCTL5 Register ($0065)
;   7  0     Not implemented
;   6  S8CM=0     4 conversions
;   5  SCAN =0    one set of 4 
;   4  MULT =0    single channel
;  3-0 CD-A =0001 Mux addr PAD7-0
Init ldaa  #$80    ;Turn on A/D
     staa  ATDCTL2 ;A/D power up
     rts           ;E clk timing
A2D  staa  ATDCTL5 ;Start A/D
Loop brclr ATDSTAT,$80,Loop  
     ldaa  ADR0H  ;first result
     rts

;