312 lines
6.9 KiB
ArmAsm
312 lines
6.9 KiB
ArmAsm
;================================
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;================================
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; mockingboard KR4 interrupt handler
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;================================
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;================================
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; On Apple II/6502 the interrupt handler jumps to address in 0xfffe
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; This is in the ROM, which saves the registers
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; on older IIe it saved A to $45 (which could mess with DISK II)
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; newer IIe doesn't do that.
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; It then calculates if it is a BRK or not (which trashes A)
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; Then it sets up the stack like an interrupt and calls 0x3fe
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interrupt_handler:
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; pha ; save A ; 3
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txa
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pha
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tya
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pha
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; Should we save X and Y too?
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; inc $0404 ; debug (flashes char onscreen)
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bit $C404 ; clear 6522 interrupt by reading T1C-L ; 4
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lda DONE_PLAYING ; 3
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beq mb_play_music ; if song done, don't play music ; 3/2nt
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jmp exit_interrupt ; 3
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;============
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; 13
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mb_play_music:
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;======================================
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; Write frames to Mockingboard
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;======================================
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; actually plays frame loaded at end of
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; last interrupt, so 20ms behind?
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mb_write_frame:
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ldx #0 ; set up reg count ; 2
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;============
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; 2
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;==================================
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; loop through the 14 registers
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; reading the value, then write out
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;==================================
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; This is actually a KRW4 player
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; plays 4 channels, right is 123, left is 143
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; used for converted MOD files
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; To save space also no envelope support
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mb_write_loop:
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lda REGISTER_DUMP,X ; load register value ; 4
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cmp REGISTER_OLD,X ; compare with old values ; 4
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beq mb_no_write_left ; 3/2nt
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; address
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stx MOCK_6522_ORA1 ; put address on PA1 ; 4
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lda #MOCK_AY_LATCH_ADDR ; latch_address for PB1 ; 2
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sta MOCK_6522_ORB1 ; latch_address on PB1 ; 4
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lda #MOCK_AY_INACTIVE ; go inactive ; 2
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sta MOCK_6522_ORB1 ; 4
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; value
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lda REGISTER_DUMP,X ; load register value ; 4
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sta MOCK_6522_ORA1 ; put value on PA1 ; 4
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lda #MOCK_AY_WRITE ; ; 2
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sta MOCK_6522_ORB1 ; write on PB1 ; 4
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lda #MOCK_AY_INACTIVE ; go inactive ; 2
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sta MOCK_6522_ORB1 ; 4
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mb_no_write_left:
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lda REGISTER_DUMP2,X; load register value ; 4
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cmp REGISTER_OLD2,X ; compare with old values ; 4
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beq mb_no_write_right ; 3/2nt
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; address
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stx MOCK_6522_ORA2 ; put address on PA2 ; 4
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lda #MOCK_AY_LATCH_ADDR ; latch_address for PB1 ; 2
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sta MOCK_6522_ORB2 ; latch_address on PB2 ; 4
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lda #MOCK_AY_INACTIVE ; go inactive ; 2
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sta MOCK_6522_ORB2 ; 4
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; value
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lda REGISTER_DUMP2,X ; load register value ; 4
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sta MOCK_6522_ORA2 ; put value on PA2 ; 4
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lda #MOCK_AY_WRITE ; ; 2
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sta MOCK_6522_ORB2 ; write on PB2 ; 4
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lda #MOCK_AY_INACTIVE ; go inactive ; 2
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sta MOCK_6522_ORB2 ; 4
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mb_no_write_right:
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inx ; point to next register ; 2
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cpx #12 ; if 12 we're done ; 2
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bmi mb_write_loop ; otherwise, loop ; 3/2nt
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;=====================================
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; Copy registers to old
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;=====================================
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ldx #13 ; 2
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mb_reg_copy:
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lda REGISTER_DUMP,X ; load register value ; 4
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sta REGISTER_OLD,X ; compare with old values ; 4
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lda REGISTER_DUMP2,X; load register value ; 4
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sta REGISTER_OLD2,X ; compare with old values ; 4
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dex ; 2
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bpl mb_reg_copy ; 2nt/3
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;===================================
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; Load all 14 registers in advance
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;===================================
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; note, assuming not cross page boundary, not any slower
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; then loading from zero page?
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mb_load_values:
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ldx #0 ; set up reg count ; 2
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ldy MB_CHUNK_OFFSET ; get chunk offset ; 3
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;=============
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; 5
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mb_load_loop:
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lda (INL),y ; load register value ; 5
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cpx #11
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bne mb_load12
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mb_load11:
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sta REGISTER_DUMP2+2
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jmp mb_done_load
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mb_load12:
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cpx #12
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bne mb_load13
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sta REGISTER_DUMP2+3
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jmp mb_done_load
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mb_load13:
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cpx #13
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bne mb_regular_load
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sta REGISTER_DUMP2+9
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jmp mb_done_load
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mb_regular_load:
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sta REGISTER_DUMP,X ; 4
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sta REGISTER_DUMP2,X
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mb_done_load:
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;====================
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; point to next page
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;====================
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clc ; point to next interleaved ; 2
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lda INH ; page by adding CHUNKSIZE (3/1); 3
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adc CHUNKSIZE ; 3
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sta INH ; 3
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inx ; point to next register ; 2
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cpx #14 ; if 14 we're done ; 2
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bmi mb_load_loop ; otherwise, loop ; 3/2nt
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;============
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; 18
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;=========================================
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; if A_COARSE_TONE is $ff then we are done
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lda A_COARSE_TONE ; 3
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bpl mb_not_done ; 3/2nt
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quiet_exit:
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lda #1 ; set done playing ; 2
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sta DONE_PLAYING
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jsr clear_ay_both
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;=====================================
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; clear register area
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;=====================================
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ldx #13 ; 2
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lda #0 ; 2
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mb_clear_reg:
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sta REGISTER_DUMP,X ; clear register value ; 4
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sta REGISTER_OLD,X ; clear old values ; 4
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dex ; 2
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bpl mb_clear_reg ; 2nt/3
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jmp exit_interrupt
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mb_not_done:
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;==============================================
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; incremement offset. If 0 move to next chunk
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;==============================================
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increment_offset:
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inc MB_CHUNK_OFFSET ; increment offset ; 5
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bne back_to_first_reg ; if not zero, done ; 3/2nt
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;=====================
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; move to next state
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;=====================
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clc
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rol DECODER_STATE ; next state ; 5
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; 20 -> 40 -> 80 -> c+00
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bcs wraparound_to_a ; 3/2nt
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bit DECODER_STATE ;bit7->N bit6->V
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bvs back_to_first_reg ; do nothing on B ; 3/2nt
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start_c:
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lda #1
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sta CHUNKSIZE
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; setup next three chunks of song
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lda #1 ; start decompressing
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sta DECOMPRESS_TIME ; outside of handler
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jmp back_to_first_reg
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wraparound_to_a:
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lda #$3
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sta CHUNKSIZE
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lda #$20
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sta DECODER_STATE
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sta COPY_TIME ; start copying
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lda DECOMPRESS_TIME
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beq blah
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lda #1
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sta DECODE_ERROR
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blah:
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;==============================
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; After 14th reg, reset back to
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; read R0 data
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;==============================
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back_to_first_reg:
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lda #0 ; 2
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bit DECODER_STATE ; 3
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bmi back_to_first_reg_c ; 2nt/3
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bvc back_to_first_reg_a ; 2nt/3
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back_to_first_reg_b:
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lda #$1 ; offset by 1
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back_to_first_reg_a:
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clc ; 2
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adc #>UNPACK_BUFFER ; in proper chunk 1 or 2 ; 2
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jmp update_r0_pointer ; 3
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back_to_first_reg_c:
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lda #>(UNPACK_BUFFER+$2A00) ; in linear C area ; 2
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update_r0_pointer:
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sta INH ; update r0 pointer ; 3
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;=================================
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; Finally done with this interrupt
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;=================================
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done_interrupt:
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;=====================
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; Increment Frame Count
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; OK if this wraps
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;=====================
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inc FRAME_COUNT ; 5
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ldy #$0
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;=====================
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; print lyrics
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;=====================
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jsr display_lyrics
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exit_interrupt:
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pla ; restore a ; 4
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tay
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pla
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tax
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lda $45 ; restore A saved by firmware
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; needed on older (pre-enhanced IIe)
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rti ; return from interrupt ; 6
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;============
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; typical
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; ???? cycles
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REGISTER_OLD:
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.byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0
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REGISTER_OLD2:
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.byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0
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