mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-11-16 23:20:43 +00:00
162 lines
3.9 KiB
ArmAsm
162 lines
3.9 KiB
ArmAsm
;================================
|
|
;================================
|
|
; mockingboard interrupt handler
|
|
;================================
|
|
;================================
|
|
; On Apple II/6502 the interrupt handler jumps to address in 0xfffe
|
|
; This is in the ROM, which saves the registers
|
|
; on older IIe it saved A to $45 (which could mess with DISK II)
|
|
; newer IIe doesn't do that.
|
|
; It then calculates if it is a BRK or not (which trashes A)
|
|
; Then it sets up the stack like an interrupt and calls 0x3fe
|
|
|
|
; Note: the IIc is much more complicated
|
|
; its firmware tries to decode the proper source
|
|
; based on various things, including screen hole values
|
|
; we bypass that by switching out ROM and replacing the
|
|
; $fffe vector with this, but that does mean we have
|
|
; to be sure status flag and accumulator set properly
|
|
|
|
interrupt_handler:
|
|
php ; save status flags
|
|
cld ; clear decimal mode
|
|
pha ; save A ; 3
|
|
; A is saved in $45 by firmware
|
|
txa
|
|
pha ; save X
|
|
tya
|
|
pha ; save Y
|
|
|
|
; inc $0404 ; debug (flashes char onscreen)
|
|
|
|
|
|
pt3_irq_smc1:
|
|
bit MOCK_6522_T1CL ; clear 6522 interrupt by reading T1C-L ; 4
|
|
|
|
lda DONE_PLAYING ; 3
|
|
beq ym_play_music ; if song done, don't play music ; 3/2nt
|
|
jmp done_pt3_irq_handler ; 3
|
|
;============
|
|
; 13
|
|
|
|
ym_play_music:
|
|
|
|
lda BASE_FRAME_L
|
|
sta CURRENT_FRAME_L
|
|
lda BASE_FRAME_H
|
|
sta CURRENT_FRAME_H
|
|
|
|
ldx #0
|
|
frame_loop:
|
|
ldy #0
|
|
lda (CURRENT_FRAME_L),Y
|
|
cmp #$ff
|
|
bne all_good
|
|
cpx #1 ; see if A coarse is $FF
|
|
beq go_next_chunk ; if so, end of song, loop
|
|
|
|
all_good:
|
|
jsr update_ay_register
|
|
|
|
clc
|
|
lda CURRENT_FRAME_H
|
|
adc #$4
|
|
sta CURRENT_FRAME_H
|
|
|
|
inx
|
|
cpx #12
|
|
bne frame_loop
|
|
|
|
|
|
inc BASE_FRAME_L
|
|
bne not_oflo
|
|
|
|
inc BASE_FRAME_H
|
|
lda BASE_FRAME_H
|
|
cmp #$D4
|
|
bne not_oflo
|
|
|
|
go_next_chunk:
|
|
inc CURRENT_CHUNK
|
|
jsr load_song_chunk
|
|
|
|
|
|
not_oflo:
|
|
|
|
jmp exit_interrupt
|
|
|
|
;=================================
|
|
; Finally done with this interrupt
|
|
;=================================
|
|
|
|
quiet_exit:
|
|
stx DONE_PLAYING
|
|
jsr clear_ay_both
|
|
|
|
; mute the sound
|
|
|
|
ldx #7
|
|
lda #$ff
|
|
jsr update_ay_register
|
|
|
|
|
|
exit_interrupt:
|
|
|
|
pla
|
|
tay ; restore Y
|
|
pla
|
|
tax ; restore X
|
|
pla ; restore a ; 4
|
|
|
|
; on II+/IIe (but not IIc) we need to do this?
|
|
interrupt_smc:
|
|
lda $45 ; restore A
|
|
plp
|
|
|
|
rti ; return from interrupt ; 6
|
|
|
|
;============
|
|
; typical
|
|
; ???? cycles
|
|
|
|
|
|
|
|
|
|
|
|
;=========================
|
|
; update ay_register
|
|
; reg in X
|
|
; value in A
|
|
|
|
update_ay_register:
|
|
|
|
pt3_irq_smc2:
|
|
stx MOCK_6522_ORA1 ; put address on PA1 ; 4
|
|
stx MOCK_6522_ORA2 ; put address on PA2 ; 4
|
|
ldy #MOCK_AY_LATCH_ADDR ; latch_address for PB1 ; 2
|
|
pt3_irq_smc3:
|
|
sty MOCK_6522_ORB1 ; latch_address on PB1 ; 4
|
|
sty MOCK_6522_ORB2 ; latch_address on PB2 ; 4
|
|
ldy #MOCK_AY_INACTIVE ; go inactive ; 2
|
|
pt3_irq_smc4:
|
|
sty MOCK_6522_ORB1 ; 4
|
|
sty MOCK_6522_ORB2 ; 4
|
|
|
|
; value
|
|
pt3_irq_smc5:
|
|
sta MOCK_6522_ORA1 ; put value on PA1 ; 4
|
|
sta MOCK_6522_ORA2 ; put value on PA2 ; 4
|
|
lda #MOCK_AY_WRITE ; ; 2
|
|
pt3_irq_smc6:
|
|
sta MOCK_6522_ORB1 ; write on PB1 ; 4
|
|
sty MOCK_6522_ORB1 ; 4
|
|
pt3_irq_smc7:
|
|
sta MOCK_6522_ORB2 ; write on PB2 ; 4
|
|
sty MOCK_6522_ORB2 ; 4
|
|
|
|
rts
|
|
|
|
|
|
done_pt3_irq_handler:
|
|
|