311 lines
8.6 KiB
ArmAsm
311 lines
8.6 KiB
ArmAsm
MoveLeft
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clc
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adc StartX ; Increment the virtual X-position
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jsr SetBG0XPos
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lda StartX
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lsr
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jsr SetBG1XPos
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jsr DoFrame
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rts
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MoveRight
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pha
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lda StartX
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sec
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sbc 1,s
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bpl *+5
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lda #0
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jsr SetBG0XPos
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lda StartX
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lsr
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jsr SetBG1XPos
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jsr DoFrame
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pla
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rts
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MoveUp
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clc
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adc StartY ; Increment the virtual Y-position
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jsr SetBG0YPos
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lda StartY
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lsr
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jsr SetBG1YPos
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jsr DoFrame
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rts
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MoveDown
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pha
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lda StartY
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sec
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sbc 1,s
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bpl *+5
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lda #0
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jsr SetBG0YPos
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lda StartY
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lsr
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jsr SetBG1YPos
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jsr DoFrame
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pla
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rts
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; Very simple, scroll as fast as possible
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oldOneSecondCounter ds 2
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frameCount ds 2
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lastTick ds 2
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Demo
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lda OneSecondCounter
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sta oldOneSecondCounter
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stz frameCount
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; Set a timer to fire every 16 ticks
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; lda #6
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; sta Timers
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; sta Timers+2
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; lda #UpdateBG1Rotation
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; sta Timers+4
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; Every 3 ticks (20 fps) cycle some colors
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lda #3
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sta Timers+8
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sta Timers+10
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lda #DoColorCycle
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sta Timers+12
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:loop
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PushLong #0
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_GetTick
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pla
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plx
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cmp lastTick ; Throttle to 60 fps
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beq :loop
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tax ; Calculate the increment
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sec
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sbc lastTick
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stx lastTick
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; jsr _DoTimers
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; lda #1
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; jsr MoveLeft
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jsr UpdateBG1Rotation
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; jsr DoColorCycle
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jsr DoFrame
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inc frameCount
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ldal KBD_STROBE_REG
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bit #$0080
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beq :nokey
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and #$007F
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cmp #'s'
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bne :nokey
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rts
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:nokey
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lda OneSecondCounter
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cmp oldOneSecondCounter
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beq :loop
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sta oldOneSecondCounter
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lda ScreenWidth
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cmp #150
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bcs :loop
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lda #FPSStr
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ldx #0 ; top-left corner
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ldy #$7777
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jsr DrawString
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lda frameCount
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ldx #4*4
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jsr DrawWord
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stz frameCount
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bra :loop
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FPSStr str 'FPS'
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; Move some colors around color (6 - 11) address 12 - 22
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DoColorCycle
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ldal $E19E0C
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pha
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ldal $E19E0E
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pha
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ldal $E19E10
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pha
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ldal $E19E12
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pha
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ldal $E19E14
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pha
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ldal $E19E16
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stal $E19E0C
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pla
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stal $E19E16
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pla
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stal $E19E14
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pla
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stal $E19E12
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pla
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stal $E19E10
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pla
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stal $E19E0E
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rts
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; Triggered timer to sway the background
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UpdateBG1Offset
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lda BG1OffsetIndex
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inc
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inc
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cmp #32 ; 16 entries x 2 for indexing
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bcc *+5
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sbc #32
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sta BG1OffsetIndex
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rts
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AngleUp
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lda angle
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inc
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cmp #64
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bcc *+5
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sbc #64
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sta angle
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jsr _ApplyAngle
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jsr DoFrame
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rts
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AngleDown
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lda angle
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dec
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bpl *+6
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clc
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adc #64
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sta angle
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jsr _ApplyAngle
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jsr DoFrame
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rts
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angle dw 0
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UpdateBG1Rotation
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jsr _ApplyAngle
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; Increment the angle
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lda angle
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inc
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cmp #64
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bcc *+5
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lda #0
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sta angle
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rts
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x_angles EXT
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y_angles EXT
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_ApplyAngle
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lda angle ; debug with angle = 0
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asl
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tax
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ldal x_angles,x ; load the address of addressed for this angle
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tay
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phx
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jsr _ApplyBG1XPosAngle
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plx
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ldal y_angles,x ; load the address of addresses for this angle
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tay
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jsr _ApplyBG1YPosAngle
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rts
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; A collection of 8 timers that are triggered when their countdown
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; goes below zero. Each timer takes up 8 bytes
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;
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; A timer can fire multiple times during a singular evaluation. For example, if the
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; timer delay is set to 1 and 3 VBL ticks happen, then the timer delta is -2, will fire,
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; have the delay added and get -1, fire again, increment to zero, first again and then
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; finally reset to 1.
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;
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; +0 counter decremented by the number of ticks since last run
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; +2 reset copied into counter when triggered. 0 turns off the timer.
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; +4 addr address of time routine
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; +6 reserved
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MAX_TIMERS equ 4
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Timers ds 8*MAX_TIMERS
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; Countdown the timers
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;
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; A = number of elapsed ticks
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_DoTimers
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pha
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ldx #0
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:loop
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lda Timers,x ; A zero means do not fire
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beq :skip
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sec
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sbc 1,s ; subtract the number of ticks
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sta Timers,x
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:retry beq :fire ; getting <= zero triggers
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bpl :skip
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:fire pha ; Save the counter
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phx ; Save our index
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jsr (Timers+4,x)
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plx
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pla
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clc
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adc Timers+2,x ; Add the increment
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sta Timers,x ; Store in the count
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bra :retry ; See if we have >0 ticks to wait until the next trigger
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:skip txa
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clc
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adc #8
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tax
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cpx #8*MAX_TIMERS
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bcc :loop
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pla
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rts
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