117 lines
2.6 KiB
ArmAsm
117 lines
2.6 KiB
ArmAsm
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pt3_irq_handler:
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pt3_irq_smc1:
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bit MOCK_6522_T1CL ; clear 6522 interrupt by reading T1C-L ; 4
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lda DONE_PLAYING ; 3
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beq pt3_play_music ; if song done, don't play music ; 3/2nt
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jmp done_pt3_irq_handler ; 3
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;============
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; 13
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pt3_play_music:
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; decode a frame of music
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jsr pt3_make_frame
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; handle song over condition
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lda DONE_SONG
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beq mb_write_frame ; if not done, continue
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lda LOOP ; see if looping
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beq move_to_next
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pt3_loop_smc:
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lda #$d1 ; looping, move to loop location
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; non-zero to avoid the temptation
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; to merge with following lda #$0
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sta current_pattern_smc+1
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lda #$0
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sta current_line_smc+1
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sta current_subframe_smc+1
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sta DONE_SONG ; undo the next song
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beq done_pt3_irq_handler ; branch always
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move_to_next:
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; same as "press right"
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ldx #$20
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jmp quiet_exit
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;======================================
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; Write frames to Mockingboard
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;======================================
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; for speed could merge this into
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; the decode code
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mb_write_frame:
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tax ; set up reg count ; 2
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;============
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; 2
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;==================================
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; loop through the 14 registers
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; reading the value, then write out
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;==================================
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mb_write_loop:
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lda AY_REGISTERS,X ; load register value ; 4
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; special case R13. If it is 0xff, then don't update
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; otherwise might spuriously reset the envelope settings
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cpx #13 ; 2
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bne mb_not_13 ; 3/2nt
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cmp #$ff ; 2
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beq mb_skip_13 ; 3/2nt
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;============
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; typ 5
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mb_not_13:
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; address
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pt3_irq_smc2:
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stx MOCK_6522_ORA1 ; put address on PA1 ; 4
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stx MOCK_6522_ORA2 ; put address on PA2 ; 4
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ldy #MOCK_AY_LATCH_ADDR ; latch_address for PB1 ; 2
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pt3_irq_smc3:
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sty MOCK_6522_ORB1 ; latch_address on PB1 ; 4
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sty MOCK_6522_ORB2 ; latch_address on PB2 ; 4
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ldy #MOCK_AY_INACTIVE ; go inactive ; 2
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pt3_irq_smc4:
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sty MOCK_6522_ORB1 ; 4
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sty MOCK_6522_ORB2 ; 4
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; value
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pt3_irq_smc5:
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sta MOCK_6522_ORA1 ; put value on PA1 ; 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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pt3_irq_smc6:
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sta MOCK_6522_ORB1 ; write on PB1 ; 4
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sty MOCK_6522_ORB1 ; 4
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pt3_irq_smc7:
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sta MOCK_6522_ORB2 ; write on PB2 ; 4
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sty MOCK_6522_ORB2 ; 4
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;===========
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; 56
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mb_no_write:
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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_write_loop ; otherwise, loop ; 3/2nt
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;============
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; 7
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mb_skip_13:
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;=================================
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; Finally done with this interrupt
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;=================================
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done_pt3_irq_handler:
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