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chiptune_player: copy on phase A

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This commit is contained in:
Vince Weaver 2018-02-24 23:28:45 -05:00
parent e88e773563
commit d4eae9a720
1 changed files with 34 additions and 2 deletions
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36
chiptune_player/interrupt_handler.s
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@ -14,7 +14,7 @@ interrupt_handler:
pha ; save A ; 3
; Should we save X and Y too?
; inc $0404 ; debug
; inc $0404 ; debug (flashes char onscreen)
bit $C404 ; clear 6522 interrupt by reading T1C-L ; 4
@ -100,7 +100,7 @@ mb_not_done:
cpx #13 ; 2
bne mb_not_13 ; 3/2nt
cmp #$ff ; 2
beq increment_offset ; 3/2nt
beq phase_specific ; 3/2nt
mb_not_13:
sta MB_VALUE ; 3
@ -131,6 +131,38 @@ mb_not_13:
; *13= 1235?
;==============================================
; phase_specific action
;==============================================
; if phase is A and OFFSET&0x0f==0 then do a copy
; if phase is B, do nothing
; if phase is C, do a decompress step
phase_specific:
lda #0 ; 2
bit DECODER_STATE ; Z=A, V=B, N=C ; 3
bvs increment_offset
beq handle_copy
decompress_step:
jmp increment_offset
handle_copy:
lda MB_CHUNK_OFFSET
and #$0f
bne increment_offset
lda COPY_OFFSET
cmp #$14
beq increment_offset
jsr page_copy
inc COPY_OFFSET ; (opt: make subtract?)
;==============================================
; incremement offset. If 0 move to next chunk
;==============================================