133 lines
1.8 KiB
ArmAsm
133 lines
1.8 KiB
ArmAsm
play_frame:
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;===============================
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;===============================
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; things that happen every frame
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;===============================
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;===============================
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;=================================
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; inc frame counter
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inc FRAME
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;=================================
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; rotate through channel A volume
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lda FRAME
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and #$7
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tay
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lda channel_a_volume,Y
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sta AY_REGS+8
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;============================
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; see if still counting down
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lda SONG_COUNTDOWN
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bpl done_update_song
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set_notes_loop:
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;==================
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; load next byte
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ldy SONG_OFFSET
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track_smc:
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lda track4,Y
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;==================
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; see if hit end
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cmp #$ff
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bne not_end
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;====================================
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; if at end, loop back to beginning
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inc WHICH_TRACK
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ldy WHICH_TRACK
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cpy #5
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bne no_wrap
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ldy #1
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sty WHICH_TRACK
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no_wrap:
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lda tracks_l,Y
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sta track_smc+1
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lda tracks_h,Y
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sta track_smc+2
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lda #0
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sta SONG_OFFSET
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beq set_notes_loop ; bra
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not_end:
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; NNNNNEEC -- c=channel, e=end, n=note
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pha ; save note
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and #1
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tax
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ldy #$0E
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sty AY_REGS+8,X ; $08 set volume A,B
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asl
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tax ; put channel offset in X
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pla ; restore note
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pha
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and #$6
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lsr
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tay
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lda lengths,Y
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sta SONG_COUNTDOWN ;
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pla
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lsr
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lsr
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lsr ; get note in A
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tay ; lookup in table
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lda frequencies_high,Y
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sta AY_REGS+1,X
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; sta $500,X
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lda frequencies_low,Y
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sta AY_REGS,X ; set proper register value
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; visualization
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blah_urgh:
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sta $400,Y
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inc blah_urgh+1
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;============================
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; point to next
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; assume less than 256 bytes
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inc SONG_OFFSET
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done_update_song:
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dec SONG_COUNTDOWN
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bmi set_notes_loop
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bpl skip_data
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channel_a_volume:
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.byte 14,14,14,14,11,11,10,10
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lengths:
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.byte 0*8,1*8,2*8,4*8
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tracks_l:
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.byte <track4,<track0,<track1,<track2,<track3
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tracks_h:
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.byte >track4,>track0,>track1,>track2,>track3
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skip_data:
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