Timer Functions - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 390

dec rep_cnt

beq done ; if not finished playing, reestablish

ldx #score ; pointers and loop count

ldy #duration ; “

movb #notes,ip ; “

movw 0,x,delay ; get the first note delay count

ldd TCNT ; play the first note

addd delay ; “

std TC5

bra forever

done swi
; ********************************************************************************
; The OC5 interrupt service routine simply starts a new OC5 operation.
; ********************************************************************************
oc5_isr ldd TC5

addd delay

std TC5

rti
; ********************************************************************************
; The following subroutine creates a time delay which is equal to [Y] times
; 10 ms. The timer prescaler is 1:8.
; ********************************************************************************
delayby10ms

bset TIOS,OC0 ; enable OC0

ldd TCNT

again1 addd #30000 ; start an output-compare operation

std TC0 ; with 10-ms time delay

brclr TFLG1,C0F,*

ldd TC0

dbne y,again1

bclr TIOS,OC0 ; disable OC0

rts
; ********************************************************************************
; This table determines the frequency of each note.
; ********************************************************************************
score dc.w D4,B3,G3,B3,D4,G4,B4,A4,G4,B3,C4S
dc.w D4,ZZ,D4,ZZ,D4,B4,A4,G4,F4S,E4,F4S,G4,ZZ,G4,D4,B3,G3
dc.w D4,B3,G3,B3,D4,G4,B4,A4,G4,B3,C4S,D4,ZZ,D4,ZZ,D4
dc.w B4,A4,G4,F4S,E4,F4S,G4,ZZ,G4,D4,B3,G3,B4,ZZ,B4
dc.w B4,C5,D5,ZZ,D5,C5,B4,A4,B4,C5,ZZ,C5,ZZ,C5,B4,A4,G4
dc.w F4S,E4,F4S,G4,B3,C4S,D4,ZZ,D4,G4,ZZ,G4,ZZ,G4,F4S
dc.w E4,ZZ,E4,ZZ,E4,A4,C5,B4,A4,G4,ZZ,G4,F4S,D4,ZZ,D4
dc.w G4,A4,B4,C5,D5,G4,A4,B4,C5,A4,G4
; ********************************************************************************
; Each of the following entries multiplied by 10 ms gives the duration of a note.
; ********************************************************************************
duration

dc.w 30,10,40,40,40,80,30,10,40,40,40

dc.w 80, 3,20,3,20,60,20,40,80,20,20,40,3,40,40,40,40

dc.w 30,10,40,40,40,80,30,10,40,40,40,80,3,20,3,20

dc.w 60,20,40,80,20,20,40,3,40,40,40,40,20,3,20