222 lines
3.9 KiB
ArmAsm
222 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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; 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 ; save status flags
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cld ; clear decimal mode
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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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.include "pt3_lib_irq_handler.s"
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;==============================================
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; only update time counter if not done playing
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;==============================================
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lda DONE_PLAYING ; 3
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bne check_keyboard
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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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jsr pt3_toggle_freq_conversion
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; update text on screen
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lda convert_177_smc1
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cmp #$18
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beq at_MHz
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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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; on II+/IIe (but not IIc) we need to do this?
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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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