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251 lines
6.2 KiB
ArmAsm
251 lines
6.2 KiB
ArmAsm
; Mockingboad programming:
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; + Has two 6522 I/O chips connected to two AY-3-8910 chips
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; + Optionally has some speech chips controlled via the outport on the AY
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; + Often in slot 4
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; TODO: how to auto-detect?
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; References used:
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; http://macgui.com/usenet/?group=2&id=8366
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; 6522 Data Sheet
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; AY-3-8910 Data Sheet
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;========================
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; Mockingboard card
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; Essentially two 6522s hooked to the Apple II bus
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; Connected to AY-3-8910 chips
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; PA0-PA7 on 6522 connected to DA0-DA7 on AY
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; PB0 on 6522 connected to BC1
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; PB1 on 6522 connected to BDIR
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; PB2 on 6522 connected to RESET
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; left speaker
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MOCK_6522_ORB1 = $C400 ; 6522 #1 port b data
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MOCK_6522_ORA1 = $C401 ; 6522 #1 port a data
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MOCK_6522_DDRB1 = $C402 ; 6522 #1 data direction port B
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MOCK_6522_DDRA1 = $C403 ; 6522 #1 data direction port A
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MOCK_6522_T1CL = $C404 ; 6522 #1 t1 low order latches
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MOCK_6522_T1CH = $C405 ; 6522 #1 t1 high order counter
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MOCK_6522_T1LL = $C406 ; 6522 #1 t1 low order latches
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MOCK_6522_T1LH = $C407 ; 6522 #1 t1 high order latches
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MOCK_6522_T2CL = $C408 ; 6522 #1 t2 low order latches
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MOCK_6522_T2CH = $C409 ; 6522 #1 t2 high order counters
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MOCK_6522_SR = $C40A ; 6522 #1 shift register
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MOCK_6522_ACR = $C40B ; 6522 #1 auxilliary control register
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MOCK_6522_PCR = $C40C ; 6522 #1 peripheral control register
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MOCK_6522_IFR = $C40D ; 6522 #1 interrupt flag register
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MOCK_6522_IER = $C40E ; 6522 #1 interrupt enable register
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MOCK_6522_ORANH = $C40F ; 6522 #1 port a data no handshake
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; right speaker
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MOCK_6522_ORB2 = $C480 ; 6522 #2 port b data
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MOCK_6522_ORA2 = $C481 ; 6522 #2 port a data
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MOCK_6522_DDRB2 = $C482 ; 6522 #2 data direction port B
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MOCK_6522_DDRA2 = $C483 ; 6522 #2 data direction port A
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; AY-3-8910 commands on port B
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; RESET BDIR BC1
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MOCK_AY_RESET = $0 ; 0 0 0
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MOCK_AY_INACTIVE = $4 ; 1 0 0
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MOCK_AY_READ = $5 ; 1 0 1
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MOCK_AY_WRITE = $6 ; 1 1 0
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MOCK_AY_LATCH_ADDR = $7 ; 1 1 1
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;========================
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; Mockingboard Init
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;========================
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; Initialize the 6522s
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; set the data direction for all pins of PortA/PortB to be output
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mockingboard_init:
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lda #$ff ; all output (1)
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mock_init_smc1:
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sta MOCK_6522_DDRB1
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sta MOCK_6522_DDRA1
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mock_init_smc2:
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sta MOCK_6522_DDRB2
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sta MOCK_6522_DDRA2
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rts
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;===================================
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;===================================
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; Reset Both AY-3-8910s
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;===================================
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;===================================
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;======================
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; Reset Left AY-3-8910
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;======================
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reset_ay_both:
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lda #MOCK_AY_RESET
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reset_ay_smc1:
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sta MOCK_6522_ORB1
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lda #MOCK_AY_INACTIVE
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reset_ay_smc2:
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sta MOCK_6522_ORB1
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;======================
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; Reset Right AY-3-8910
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;======================
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;reset_ay_right:
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;could be merged with both
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lda #MOCK_AY_RESET
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reset_ay_smc3:
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sta MOCK_6522_ORB2
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lda #MOCK_AY_INACTIVE
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reset_ay_smc4:
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sta MOCK_6522_ORB2
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rts
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; Write sequence
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; Inactive -> Latch Address -> Inactive -> Write Data -> Inactive
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;=========================================
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; Write Right/Left to save value AY-3-8910
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;=========================================
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; register in X
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; value in MB_VALUE
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write_ay_both:
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; address
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write_ay_smc1:
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stx MOCK_6522_ORA1 ; put address on PA1 ; 3
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stx MOCK_6522_ORA2 ; put address on PA2 ; 3
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lda #MOCK_AY_LATCH_ADDR ; latch_address on PB1 ; 2
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write_ay_smc2:
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sta MOCK_6522_ORB1 ; latch_address on PB1 ; 3
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sta MOCK_6522_ORB2 ; latch_address on PB2 ; 3
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ldy #MOCK_AY_INACTIVE ; go inactive ; 2
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write_ay_smc3:
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sty MOCK_6522_ORB1 ; 3
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sty MOCK_6522_ORB2 ; 3
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; value
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lda MB_VALUE ; 3
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write_ay_smc4:
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sta MOCK_6522_ORA1 ; put value on PA1 ; 3
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sta MOCK_6522_ORA2 ; put value on PA2 ; 3
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lda #MOCK_AY_WRITE ; ; 2
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write_ay_smc5:
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sta MOCK_6522_ORB1 ; write on PB1 ; 3
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sta MOCK_6522_ORB2 ; write on PB2 ; 3
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write_ay_smc6:
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sty MOCK_6522_ORB1 ; 3
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sty MOCK_6522_ORB2 ; 3
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rts ; 6
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;===========
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; 51
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;=======================================
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; clear ay -- clear all 14 AY registers
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; should silence the card
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;=======================================
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clear_ay_both:
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ldx #14
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lda #0
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sta MB_VALUE
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clear_ay_left_loop:
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jsr write_ay_both
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dex
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bpl clear_ay_left_loop
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rts
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;=============================
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; Setup
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;=============================
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mockingboard_setup_interrupt:
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;===========================
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; Check for Apple IIc
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;===========================
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; it does interrupts differently
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lda $FBB3 ; IIe and newer is $06
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cmp #6
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beq apple_iie_or_newer
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jmp done_apple_detect
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apple_iie_or_newer:
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lda $FBC0 ; 0 on a IIc
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bne done_apple_detect
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apple_iic:
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; activate IIc mockingboard?
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; this might only be necessary to allow detection
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; I get the impression the Mockingboard 4c activates
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; when you access any of the 6522 ports in Slot 4
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lda #$ff
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; don't bother patching these, IIc mockingboard always slot 4?
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sta MOCK_6522_DDRA1
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sta MOCK_6522_T1CL
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; bypass the firmware interrupt handler
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; should we do this on IIe too? probably faster
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sei ; disable interrupts
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lda $c08b ; disable ROM (enable language card)
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lda $c08b
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lda #<interrupt_handler
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sta $fffe
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lda #>interrupt_handler
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sta $ffff
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lda #$EA ; nop out the "lda $45" in the irq hand
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sta interrupt_smc
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sta interrupt_smc+1
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done_apple_detect:
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;=========================
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; Setup Interrupt Handler
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;=========================
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; Vector address goes to 0x3fe/0x3ff
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; FIXME: should chain any existing handler
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lda #<interrupt_handler
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sta $03fe
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lda #>interrupt_handler
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sta $03ff
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;============================
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; Enable 50Hz clock on 6522
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;============================
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; 4fe7 / 1e6 = .020s, 50Hz
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; 9c40 / 1e6 = .040s, 25Hz
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; 411a / 1e6 = .016s, 60Hz
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sei ; disable interrupts just in case
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lda #$40 ; Continuous interrupts, don't touch PB7
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setup_irq_smc1:
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sta MOCK_6522_ACR ; ACR register
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lda #$7F ; clear all interrupt flags
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setup_irq_smc2:
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sta MOCK_6522_IER ; IER register (interrupt enable)
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lda #$C0
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setup_irq_smc3:
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sta MOCK_6522_IFR ; IFR: 1100, enable interrupt on timer one oflow
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setup_irq_smc4:
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sta MOCK_6522_IER ; IER: 1100, enable timer one interrupt
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lda #$E7
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setup_irq_smc5:
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sta MOCK_6522_T1CL ; write into low-order latch
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lda #$4f
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setup_irq_smc6:
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sta MOCK_6522_T1CH ; write into high-order latch,
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; load both values into counter
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; clear interrupt and start counting
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rts
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