chap6.asm

Motorola 6812芯片开发的接口程序。

; Chapter 6 6812 assembly language programs
; Jonathan W. Valvano
; This software accompanies the book,
; Real Time Embedded Systems published by Brooks Cole
;

; Program 6.1. Initialization of a periodic interrupt using input capture and an external clock.
; MC68HC812A4
;external signal to PT3/IC3
TIME rmb  2      ;every 1 ms
Init sei         ;make atomic
     bclr TIOS,$08 ;PT3=input capture
     clr  DDRT     ;PT3 is input
     movb #$80,TSCR ;enable TCNT
     movb #$32,TMSK2 ; 500 ns clk
     ldaa TCTL4  ;old value
     anda #$7F   ;Clear EDG3B=0
     oraa #$40   ;EDG3BA =01 
     staa TCTL4  ;on rise of IC3
     bset TMSK1,$08  ;Arm IC3F 
     movw #0,TIME    ;init global
     movb #$08,TFLG1 ;clear IC3F 
     cli         ;enable
     rts

; Program 6.2. Periodic interrupt using input capture and an external clock.
; MC68HC812A4
IC3Han brset #$08,TFLG1,ClkHan   [4] 
       swi
ClkHan movb #$08,TFLG1 ;clr IC3F [4]
       ldx  TIME                 [3]                                 
       inx                       [1]                                 
       stx  TIME                 [3]                                 
       rti
       org  $FFE8  ;timer channel 3
       fdb  IC3Han

;  Program 6.4. Initialization for period measurement.
; MC68HC812A4
;external signal to PT1/IC1
Period rmb  2   ;units 500 ns
First  rmb  2   ;TCNT at first edge
Done   rmb  1   ;set each rising
Init sei            ;make atomic
     bclr TIOS,$02  ;PT1=input capture
     bclr DDRT,$02  ;PT1 is input
     movb #$80,TSCR ;enable TCNT
     movb #$32,TMSK2 ;500ns clk
     ldaa TCTL4  ;old value
     anda #$F3   ;Clear EDG1B=0
     oraa #$04   ;EDG1BA =01 
     staa TCTL4  ;on rise of IC1
     movw TCNT,First ;init global
     clr  Done
     movb #$02,TFLG1 ;clear IC1F
     bset TMSK1,$02  ;Arm IC1F 
     cli             ;enable
     rts

;  Program 6.5. ISR for period measurement.
; MC68HC812A4
IC1Han movb #$08,TFLG1 ;clear C3F [4]
       ldd  TC1                   [3]                                 
       subd First                 [3]                                 
       std  Period                [3]
       movw TC1,First             [6]
       movb #$FF,Done             [4]                                 
       rti                        [8]
       org  $FFEC  ;timer channel 1
       fdb  IC1Han

;  Program 6.11. Ritual written in assembly language for the pulse width measurement.
; MC68HC812A4
; B=PB7,  Q=PT2/IC2
Init   bclr TIOS,$04  ;PT2=input capt.
       movb #$90,TSCR ;enable, fast clr
       movb #$32,TMSK2 ;500 ns clk
       clr  TMSK1      ;gadfly, C2I=0
       bclr DDRB,$80
       rts

;  Program 6.12. Assembly language pulse width measurement.
; MC68HC812A4
; return Reg D as R in Kohm 
Meas   movb #$10,TCTL4 ;Rising edge
       movb #$04,TFLG1 ;C2F=0
       bclr PORTB,$80  ;PB7=0
       bset PORTB,$80  ;PB7=0         
First  brclr TFLG1,$04,First
;Wait for first rising edge
       ldy  TC2  ;TCNT at rising, C2F=0
       movb #$20,TCTL4 ;Falling edge
       pshy       ;Save on stack
Second brclr TFLG1,$04,Second
;Wait for next falling edge
       ldd  TC2 ;TCNT at falling  
       subd 2,SP+  
;RegD=pulse width 1000 to 2000 cyc
       subd #1000  ;0<=R<=1000Kohm
       rts

;  Program 6.19. Assembly language ritual for periodic interrupt using output compare.
; MC68HC812A4
TIME   rmb  2     ;inc every 1ms
Init   sei        ;make atomic
       bset TIOS,$20   ;OC5
       movb #$80,TSCR  ;enable 
       movb #$32,TMSK2 ;500 ns clk
       bset TMSK1,$20  ;Arm OC5
       movw #0,TIME    ;initialize
       movb #$20,TFLG1 ;clear C5F
       ldd  TCNT  ;current time
       addd #2000 ;first in 1 ms
       std  TC5 
       cli        ;enable
       rts

;  Program 6.20. Assembly language ISR for periodic interrupt using output compare.
; MC68HC812A4
OC5HAN ldx  TIME               [3]
       inx                     [1]
       stx  TIME               [2]
       movb #$20,TFLG1 ;Acknowledge 
       ldd  TC5                
       addd #2000 ;next       
       std  TC5               
       rti
       org  $FFE4
       fdb  OC5HAN

;  Program 6.22. Ritual for the assembly language implementation of the squarewave using output compare.
; MC68HC812A4
Period rmb  2    ;units 祍ec
Init   sei        ;make atomic
       bset TIOS,$08   ;OC3
       bset DDRT,$08   ;PT3 output
       movb #$80,TSCR  ;enable
       movb #$32,TMSK2 ;500 ns clk
       bset TMSK1,$08  ;Arm OC3
       bset TCTL2,$40  ;OL3=1
       bclr TCTL2,$80  ;OM3=0
       movb #$08,TFLG1 ;clear C3F
       ldd  TCNT  ;current time
       addd #50   ;first in 25祍
       std  TC3 
       cli        ;enable
       rts

;  Program 6.23. Assembly language squarewave using output compare.
; MC68HC812A4
OC3HAN movb #$08,TFLG1 ;Ack       [4]
       ldd  TC3                   [3]
       addd Period ;next          [3]
       std  TC3                   [2]
       rti                        [8]
       org  $FFE8
       fdb  OC3HAN

;  Program 6.25. Assembly language initialization pulse-width modulated squarewave using output compare.
; MC68HC812A4
High rmb  2  ;number of cycles high
Low  rmb  2  ;number of cycles low
RITUAL sei        ;make atomic
       bset TIOS,$08   ;OC3
       bset DDRT,$08   ;PT3 output
       movb #$80,TSCR  ;enable
       movb #$32,TMSK2 ;500 ns clk
       bset TMSK1,$08  ;Arm OC3
       bset TCTL2,$C0  ;OL3=1,OM3=1
       movb #$08,TFLG1 ;clear C3F
       ldd  TCNT  ;current time
       addd #50   ;first in 25祍
       std  TC3 
       cli        ;enable
       rts

;  Program 6.26. Assembly language ISR for pulse-width modulated squarewave using output compare.
; MC68HC812A4
OC3HAN movb #$08,TFLG1 ;Ack       [4]
       ldaa TCTL2  ;rise/fall?    [3]
       bita #$40                  [1]
       beq  zero                [1/3]
one    ldd  TC3                   [3]
       addd High ;now PT3 is 1    [3]
       std  TC3                   [2]
       bclr TCTL2,$40             [4]
       bra  done                  [3]
zero   ldd  TC3                   [3]
       addd Low  ;now PT3 is 0    [3]
       std  TC3                   [2]
       bset TCTL2,$40             [4]
done   rti                        [8]
       org  $FFE8
       fdb  OC3HAN