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cc65/libsrc/creativision/playsound.s
Greg King af3d4581d3 Moved Creativision's playsound() into a separate file.
It won't waste space in a cartridge if it isn't used.
2021-06-11 07:43:25 -04:00

41 lines
1.0 KiB
ArmAsm

; void __fastcall__ bios_playsound (void *a, unsigned char b);
.export _bios_playsound
.import popax
.include "creativision.inc"
songptr := $00 ; Points to current tune data
volptr := $04 ; Points to current volume table
;* Creativision Sound Player
;* Based on BIOS song player.
;*
;* Pass a pointer to a set of note triples, terminated with a tempo byte;
;* and pass the length of the triples and tempo (max 255).
;*
;* Note: tune data must be stored backwards.
_bios_playsound:
php
pha ; Save tune length
sei
lda #<$FCD5 ; BIOS decreasing-volume table
ldx #>$FCD5
sta volptr
stx volptr+1
jsr popax ; Get tune array pointer
sta songptr
stx songptr+1
pla
tay
dey ; Point to tempo byte
jmp BIOS_PLAY_SONG ; Let BIOS do its thing