84 lines
2.6 KiB
NASM
84 lines
2.6 KiB
NASM
; -----------------------------------------------------------
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; music.asm - SID music driver skeleton
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; called once per frame from wait_frame
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; music_init: clear SID registers
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; music_play: placeholder (currently silent)
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; music_mute / music_unmute: volume control
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;
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; To add music: replace music_play with a real SID player
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; routine (e.g. GoatTracker export), or write patterns into
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; this file using the SID register definitions below.
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; -----------------------------------------------------------
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; ---- SID registers ----
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SID_BASE = $d400
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SID_V1_FL = SID_BASE+0 ; voice 1 frequency low
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SID_V1_FH = SID_BASE+1 ; voice 1 frequency high
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SID_V1_PL = SID_BASE+2 ; voice 1 pulse width low
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SID_V1_PH = SID_BASE+3 ; voice 1 pulse width high
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SID_V1_CR = SID_BASE+4 ; voice 1 control (gate, waveform)
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SID_V1_AD = SID_BASE+5 ; voice 1 attack/decay
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SID_V1_SR = SID_BASE+6 ; voice 1 sustain/release
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SID_V2_FL = SID_BASE+7 ; voice 2 frequency low
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SID_V2_FH = SID_BASE+8 ; voice 2 frequency high
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SID_V2_PL = SID_BASE+9 ; voice 2 pulse width low
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SID_V2_PH = SID_BASE+10 ; voice 2 pulse width high
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SID_V2_CR = SID_BASE+11 ; voice 2 control
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SID_V2_AD = SID_BASE+12 ; voice 2 attack/decay
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SID_V2_SR = SID_BASE+13 ; voice 2 sustain/release
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SID_V3_FL = SID_BASE+14 ; voice 3 frequency low
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SID_V3_FH = SID_BASE+15 ; voice 3 frequency high
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SID_V3_PL = SID_BASE+16 ; voice 3 pulse width low
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SID_V3_PH = SID_BASE+17 ; voice 3 pulse width high
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SID_V3_CR = SID_BASE+18 ; voice 3 control
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SID_V3_AD = SID_BASE+19 ; voice 3 attack/decay
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SID_V3_SR = SID_BASE+20 ; voice 3 sustain/release
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SID_FC_LO = SID_BASE+21 ; filter cutoff low (bits 0-2)
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SID_FC_HI = SID_BASE+22 ; filter cutoff high
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SID_FCTL = SID_BASE+23 ; filter resonance + voice routing
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SID_VOL = SID_BASE+24 ; filter mode (hi nibble) + master volume (lo nibble)
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; ---- initialize SID ----
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music_init:
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ldx #24
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lda #0
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mi_clr:
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sta SID_BASE,x
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dex
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bpl mi_clr
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lda #$0f ; master volume = 15
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sta SID_VOL
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lda #0
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sta mus_muted
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rts
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; ---- play one tick: called once per frame ----
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; Replace this with a real music player routine.
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music_play:
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lda mus_muted
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bne mp_silent
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; --- insert SID player call here ---
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mp_silent:
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rts
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; ---- mute: silence SID ----
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music_mute:
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lda #$00
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sta SID_VOL
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rts
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; ---- unmute: restore volume ----
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music_unmute:
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lda #$0f
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sta SID_VOL
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rts
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; ---- state ----
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mus_muted: !byte 0 ; 1 = muted
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