chap11.asm

Motorola 6811芯片开发的接口程序。

; Chapter 11 6811 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).
; MC68HC11A8
; Analog signal connected to E1
;ADCTL Register ($1030)
;   7  CCF  =0 on a write ADCTL,
;           =1 on A/D done
;   6  0     Not implemented
;   5  SCAN =0    one set of 4 
;   4  MULT =0    single channel
;  3-0 CD-A =0001 Mux addr E1
Init ldaa  #$80   ;Turn on A/D
     staa  OPTION ;A/D power up
     rts          ;E clk timing
Samp ldx   #$1000
     ldaa  #1
     staa  $30,X  ;Start A/D
Loop brclr $30,X,$80,Loop  
     ldaa  $31,X  ;first result
     rts

;  Program 11.17. Assembly software to sample data using the A/D (variable channel).
; MC68HC11A8
; Analog signal to E7-0
;ADCTL Register ($1030)
;   7  CCF  =0 on a write ADCTL,
;           =1 on A/D done
;   6  0     Not implemented
;   5  SCAN =0    one set of 4 
;   4  MULT =0    single channel
;  3-0 CD-A Mux addr E7-0
Init ldaa  #$80   ;Turn on A/D
     staa  OPTION ;A/D power up
     rts          ;E clk timing
Samp ldx   #$1000
     staa  $30,X  ;Start A/D
Loop brclr $30,X,$80,Loop  
     ldaa  $31,X  ;first result
     rts