mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-07-05 00:28:59 +00:00
324 lines
6.2 KiB
ArmAsm
324 lines
6.2 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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; 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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; Note: the IIc is much more complicated
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; its firmware tries to decode the proper source
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; based on various things, including screen hole values
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; we bypass that by switching out ROM and replacing the
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; $fffe vector with this, but that does mean we have
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; to be sure status flag and accumulator set properly
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TIME_OFFSET = 13
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interrupt_handler:
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php
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pha ; save A ; 3
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; A is saved in $45 by firmware
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txa
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pha ; save X
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tya
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pha ; save Y
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; inc $0404 ; debug (flashes char onscreen)
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bit $C404 ; clear 6522 interrupt by reading T1C-L ; 4
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lda DONE_PLAYING ; 3
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beq pt3_play_music ; if song done, don't play music ; 3/2nt
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jmp check_keyboard ; 3
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;============
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; 13
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pt3_play_music:
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; decode a frame of music
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jsr pt3_make_frame
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; handle song over condition
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lda DONE_SONG
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beq mb_write_frame ; if not done, continue
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lda LOOP ; see if looping
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beq move_to_next
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pt3_loop_smc:
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lda #$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_interrupt ; 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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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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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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sty MOCK_6522_ORB1 ; 4
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sty MOCK_6522_ORB2 ; 4
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; value
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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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sty MOCK_6522_ORB1 ; 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_interrupt:
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;=====================
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; Update time counter
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;=====================
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; self-modifying version via qkumba
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update_time:
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inc frame_count_smc+1 ; 5
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frame_count_smc:
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lda #$0 ; 2
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eor #50 ; 3
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bne done_time ; 3/2nt
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sta frame_count_smc+1 ; 3
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ldx $7d0+TIME_OFFSET+3 ; 4
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cpx #'9'+$80 ; 2
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bne update_second_ones ; 3/2nt
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ldx $7d0+TIME_OFFSET+2 ; 4
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cpx #'5'+$80 ; 6-1 (for 60 seconds) ; 2
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bne update_second_tens ; 3/2nt
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update_minutes:
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inc $7d0+TIME_OFFSET ; 6
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inc $bd0+TIME_OFFSET ; 6
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ldx #'0'+$80-1 ; 2
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update_second_tens:
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inx ; 2
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stx $7d0+TIME_OFFSET+2 ; 4
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stx $bd0+TIME_OFFSET+2 ; 4
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ldx #'0'+$80-1 ; 2
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update_second_ones:
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inx ; 2
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stx $7d0+TIME_OFFSET+3 ; 4
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stx $bd0+TIME_OFFSET+3 ; 4
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; we don't handle > 9:59 songs yet
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done_time:
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;=============
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; 52 worst
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;=================================
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; Handle keyboard
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;=================================
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check_keyboard:
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jsr get_key
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tax
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beq exit_interrupt
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;====================
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; space pauses
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cmp #(' '+$80) ; set carry if true
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bne key_M
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key_space:
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lda #$80
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eor DONE_PLAYING
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; disable fire when paused
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sta DONE_PLAYING
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beq yes_bar
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lda #0
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beq lowbar ; branch always
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yes_bar:
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lda #7
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lowbar:
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jsr fire_setline
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ldx DONE_PLAYING
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bcs quiet_exit ; branch always
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;===========================
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; M key switches MHz mode
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key_M:
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cmp #'M'
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bne key_L ; set carry if true
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ldx #'0'+$80
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lda convert_177_smc1
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eor #$20
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sta convert_177_smc1
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sta convert_177_smc2
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sta convert_177_smc3
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sta convert_177_smc4
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sta convert_177_smc5
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cmp #$18
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beq at_MHz
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; update text on screen
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ldx #'7'+$80
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at_MHz:
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stx $7F4
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stx $BF4
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bcs done_key ; branch always
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;===========================
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; L enables loop mode
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key_L:
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cmp #'L'
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bne key_left ; set carry if true
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ldx #'/'+$80
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lda LOOP
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eor #$1
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sta LOOP
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beq music_looping
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; update text on screen
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ldx #'L'+$80
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music_looping:
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stx $7D0+18
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stx $BD0+18
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bcs done_key ; branch always
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;======================
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; left key, to prev song
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key_left:
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ldx #$40
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cmp #'A'
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beq quiet_exit
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;========================
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; right key, to next song
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key_right:
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ldx #$20
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cmp #'D'
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bne done_key
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;========================
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; stop playing for now
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; quiet down the Mockingboard
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; (otherwise will be stuck on last note)
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quiet_exit:
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stx DONE_PLAYING
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jsr clear_ay_both
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;ldx #$ff ; also mute the channel
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stx AY_REGISTERS+7 ; just in case
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done_key:
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exit_interrupt:
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pla
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tay ; restore Y
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pla
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tax ; restore X
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pla ; restore a ; 4
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; this is needed on II+/IIe not not IIc
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interrupt_smc:
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lda $45 ; restore A
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plp
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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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