dos33fsprogs/music/pt3_player/interrupt_handler.s
2023-05-15 12:26:02 -04:00

222 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
TIME_OFFSET = 13
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)
.include "pt3_lib_irq_handler.s"
;==============================================
; only update time counter if not done playing
;==============================================
lda DONE_PLAYING ; 3
bne check_keyboard
;=====================
; Update time counter
;=====================
; self-modifying version via qkumba
update_time:
inc frame_count_smc+1 ; 5
frame_count_smc:
lda #$0 ; 2
eor #50 ; 3
bne done_time ; 3/2nt
sta frame_count_smc+1 ; 3
ldx $7d0+TIME_OFFSET+3 ; 4
cpx #'9'+$80 ; 2
bne update_second_ones ; 3/2nt
ldx $7d0+TIME_OFFSET+2 ; 4
cpx #'5'+$80 ; 6-1 (for 60 seconds) ; 2
bne update_second_tens ; 3/2nt
update_minutes:
inc $7d0+TIME_OFFSET ; 6
inc $bd0+TIME_OFFSET ; 6
ldx #'0'+$80-1 ; 2
update_second_tens:
inx ; 2
stx $7d0+TIME_OFFSET+2 ; 4
stx $bd0+TIME_OFFSET+2 ; 4
ldx #'0'+$80-1 ; 2
update_second_ones:
inx ; 2
stx $7d0+TIME_OFFSET+3 ; 4
stx $bd0+TIME_OFFSET+3 ; 4
; we don't handle > 9:59 songs yet
done_time:
;=============
; 52 worst
;=================================
; Handle keyboard
;=================================
check_keyboard:
jsr get_key
tax
beq exit_interrupt
;====================
; space pauses
cmp #(' '+$80) ; set carry if true
bne key_M
key_space:
lda #$80
eor DONE_PLAYING
; disable fire when paused
sta DONE_PLAYING
beq yes_bar
lda #0
beq lowbar ; branch always
yes_bar:
lda #7
lowbar:
jsr fire_setline
ldx DONE_PLAYING
bcs quiet_exit ; branch always
;===========================
; M key switches MHz mode
key_M:
cmp #'M'
bne key_L ; set carry if true
ldx #'0'+$80
jsr pt3_toggle_freq_conversion
; update text on screen
lda convert_177_smc1
cmp #$18
beq at_MHz
ldx #'7'+$80
at_MHz:
stx $7F4
stx $BF4
bcs done_key ; branch always
;===========================
; L enables loop mode
key_L:
cmp #'L'
bne key_left ; set carry if true
ldx #'/'+$80
lda LOOP
eor #$1
sta LOOP
beq music_looping
; update text on screen
ldx #'L'+$80
music_looping:
stx $7D0+18
stx $BD0+18
bcs done_key ; branch always
;======================
; left key, to prev song
key_left:
ldx #$40
cmp #'A'
beq quiet_exit
;========================
; right key, to next song
key_right:
ldx #$20
cmp #'D'
bne done_key
;========================
; stop playing for now
; quiet down the Mockingboard
; (otherwise will be stuck on last note)
quiet_exit:
stx DONE_PLAYING
jsr clear_ay_both
;ldx #$ff ; also mute the channel
stx AY_REGISTERS+7 ; just in case
done_key:
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