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cc65/libsrc/creativision/psg.s

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; void __fastcall__ psg_outb (unsigned char b);
; void __fastcall__ psg_delay (unsigned char b);
; void psg_silence (void);
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.export _psg_outb, _psg_silence, _psg_delay
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.include "creativision.inc"
;* Let BIOS output the value.
_psg_outb := BIOS_POKE_PSG
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_psg_silence := BIOS_QUIET_PSG
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_psg_delay:
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tay
l1: lda #200
l2: sbc #1
bne l2
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lda #200
l3: sbc #1
bne l3
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dey
bne l1
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rts