Timer Functions - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 389

C4 equ 5733 ; delay count to generate C4 note (with 1:8 prescaler)

C4S equ 5412 ; delay count to generate C4S note

D4 equ 5108 ; delay count to generate D4 note (with 1:8 prescaler)

E4 equ 4551 ; delay count to generate E4 note (with 1:8 prescaler)

F4 equ 4295 ; delay count to generate F4 note (with 1:8 prescaler)

F4S equ 4054 ; delay count to generate F4S note (with 1:8 prescaler)

G4 equ 3827 ; delay count to generate G4 note (with 1:8 prescaler)

A4 equ 3409 ; delay count to generate A4 note (with 1:8 prescaler)

B4F equ 3218 ; delay count to generate B4F note (with 1:8 prescaler)

B4 equ 3037 ; delay count to generate B4 note (with 1:8 prescaler)

C5 equ 2867 ; delay count to generate C5 note (with 1:8 prescaler)

D5 equ 2554 ; delay count to generate D5 note (with 1:8 prescaler)

E5 equ 2275 ; delay count to generate E5 note (with 1:8 prescaler)

F5 equ 2148 ; delay count to generate F5 note (with 1:8 prescaler)

ZZ equ 20 ; delay count to generate an inaudible note

notes equ 118

toggle equ $04 ; value to toggle the TC5 pin

org $1000

delay ds.w 1 ; store the delay for output-compare operation

rep_cnt ds.b 1 ; repeat the song this many times

ip ds.b 1 ; remaining notes to be played

org $1500
; establish the SRAM vector address for OC5

movw #oc5_isr,UserTimerCh5

lds #$1500

movb #$FF,DDRB

movb #$90,TSCR1 ; enable TCNT, fast timer flag clear

movb #$03,TSCR2 ; set main timer prescaler to 8

bset TIOS,OC5 ; enable OC5

movb #toggle,TCTL1 ; select toggle for OC5 pin action

ldx #score ; use as a pointer to score table

ldy #duration ; points to duration table

movb #1,rep_cnt ; play the song twice

movb #notes,ip

movw 2,x 1 ,delay ; start with 0th note

ldd TCNT ; play the first note

addd delay ; “

std TC5 ; “

bset TIE,C5I ; enable OC5 interrupt

cli ; “

forever pshy ; save duration table pointer in stack

ldy 0,y ; get the duration of the current note

jsr delayby10ms ; “

puly ; get the duration pointer from stack

iny ; move the duration pointer

iny ; “

ldd 2,x 1 ; get the next note, move pointer

std delay ; “

dec ip

bne forever