79 lines
1.1 KiB
ArmAsm
79 lines
1.1 KiB
ArmAsm
play_frame:
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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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lda tracker_song,Y
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;==================
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; see if hit end
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; this song only 16 notes so valid notes always positive
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; cmp #$80
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bpl not_end
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;====================================
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; if at end, loop back to beginning
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asl ; reset song offset to 0
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sta SONG_OFFSET
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beq set_notes_loop
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not_end:
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; NNNNNNEC -- 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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tay
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and #$2
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sta SONG_COUNTDOWN ; always 2 long?
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tya
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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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