Note: The following public domain code does not contain the *waveform* or *music note* data.
Many examples of these are available in various Rainbow Magazine articles as well as in the Musica example song files.
;*********************************************************************
;* Title: PLAY.s (c) 1984 Speech Systems. Released to Public Domain.
;*********************************************************************
;* Author: Speech Systems
;*
;* Description: 4-voice player
;*
;* Documentation: See the MUSICA manual
;* pg. 15 for usage and license
;* pg. 19 for memory map and note format
;* pp. 20-22 for source
;*
;* Include Files: none
;*
;* Assembler: lwasm 1.4.2
;*
;* Revision History:
;* Rev # Date Who Comments
;* ----- ----------- ------ ---------------------------------------
;* 1.0 1984 SS Original Source From Manual
;*********************************************************************
PIA0AC equ $ff01
PIA0BC equ $ff03
PIA1AD equ $ff20
PIA1BC equ $ff23
;
org $3f40 ; ($3540 in tape version)
PLAY: lda #$3f ; set DP register ($35 in tape version)
tfr A,DP
setdp $3f ; ($35 in tape version)
lda $ff01 ; turn on TV sound port
anda #$f7
sta $ff01
lda $ff03
anda #$f7
sta $ff03
lda #$3c
sta $ff23
pshs CC ; save condition register
orcc #$50 ; disable interrupts
ldx #$4400 ; x=note pointer ($3a00 in tape version)
lda ,X+ ; load tempo from music
sta TEMPO
ldd ,X++ ; load tone table high addresses
sta <V1PT
stb <V2PT
ldd ,X++
sta <V3PT
stb <V4PT
bra NEWNT1
TEST: cmpa #$fe ; test for new wave table pointers
bne NEWNOT
ldd 0,X ; update wave table pointers
sta <V1PT
stb <V2PT
ldd 2,X
sta <V3PT
stb <V4PT
lda 4,X ; update TEMPO
sta <TEMPO
NEWNOT: leax 8,X ; advance note pointer
NEWNT1: lda ,X+ ; load note duration
bmi TEST ; if duration>$7F, not a note
beq PLAY2 ; duration=0 if end of music
PLAY1: sta <DUR
ldb <TEMPO ; save TEMPO
stb <TEMPO+1
MAIN: lda [V1PT] ; output voices to sound port
adda [V2PT]
adca [V3PT]
adca [V4PT]
sta $ff20
ldd <V1PT+1 ; increment voice pointers
addd ,x ; only the LSB and "fractional"
std <V1PT+1 ; bytes are changed
ldd <V2PT+1 ; second voice
addd 2,x
std <V2PT+1
ldd <V3PT+1 ; third voice
addd 4,x
std <V3PT+1
ldd <V4PT+1 ; fourth voice
addd 6,x
std <V4PT+1
dec <TEMPO+1 ; update tempo counter
bne WAIT
dec <DUR ; update duration counter
beq NEWNOT
ldb <TEMPO ; restore tempo counter
stb <TEMPO+1
bra MAIN
WAIT: leax 0,X ; (to equalize loop times)
leax 0,X
leax 0,X
leax 0,X
leax 0,X
bra MAIN
PLAY2: clra ; return from subroutine
tfr A,DP
puls CC,PC
V1PT rmb $3 ; voice time table pointers
V2PT rmb $3 ; only the last 2 bytes are
V3PT rmb $3 ; changed; the 3rd byte is
V4PT rmb $3 ; "fractional"
DUR rmb $1
TEMPO rmb $2
end PLAY
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