165 lines
3.9 KiB
ArmAsm
165 lines
3.9 KiB
ArmAsm
;================================
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;================================
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; mockingboard interrupt handler
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;================================
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;================================
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interrupt_handler:
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pha ; save A ; 3
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; Should we save X and Y too?
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.ifdef NOIRQ
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.else
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bit $C404 ; clear 6522 interrupt by reading T1C-L ; 4
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.endif
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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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; inlined "write_ay_both" to save up to 156 (12*13) cycles
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; unrolled
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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 ; 3/2nt
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;=============
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; typ 11
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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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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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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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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_ORB1 ; 4
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sta MOCK_6522_ORB2 ; 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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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_ORB1 ; write on PB1 ; 4
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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_ORB1 ; 4
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sta MOCK_6522_ORB2 ; 4
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;===========
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; 62
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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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; 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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dex ; 2
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bpl mb_reg_copy ; 2nt/3
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;=============
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; 171
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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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sta REGISTER_DUMP,X ; 4
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;============
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; 9
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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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; 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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lda #0 ; 2
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clc ; 2
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adc #>UNPACK_BUFFER ; in proper chunk 1 or 2 ; 2
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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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pla ; restore a ; 4
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.ifdef NOIRQ
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rts
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.else
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rti ; return from interrupt ; 6
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.endif
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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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