379 lines
7.7 KiB
ArmAsm
379 lines
7.7 KiB
ArmAsm
; VMW Minimal Mockingboard Issue Reproducer
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; ZP addresses
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MB_CHUNK_OFFSET = $94
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MB_VALUE = $91
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; left channel
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MOCK_6522_1_ORB = $C400 ; 6522 #1 port b data
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MOCK_6522_1_ORA = $C401 ; 6522 #1 port a data
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MOCK_6522_1_DDRB = $C402 ; 6522 #1 data direction port B
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MOCK_6522_1_DDRA = $C403 ; 6522 #1 data direction port A
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MOCK_6522_1_T1C_L = $C404 ; 6522 #1 Low-order counter
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MOCK_6522_1_T1C_H = $C405 ; 6522 #1 High-order counter
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MOCK_6522_1_T1L_L = $C406 ; 6522 #1 Low-order latch
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MOCK_6522_1_T1L_H = $C407 ; 6522 #1 High-order latch
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MOCK_6522_1_T2C_L = $C408 ; 6522 #1 Timer2 Low-order Latch/Counter
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MOCK_6522_1_T2C_H = $C409 ; 6522 #1 Timer2 High-order Latch/Counter
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MOCK_6522_1_SR = $C40A ; 6522 #1 Shift Register
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MOCK_6522_1_ACR = $C40B ; 6522 #1 Auxiliary Control Register
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MOCK_6522_1_PCR = $C40C ; 6522 #1 Peripheral Control Register
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MOCK_6522_1_IFR = $C40D ; 6522 #1 Interrupt Flag Register
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MOCK_6522_1_IER = $C40E ; 6522 #1 Interrupt Enable Register
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MOCK_6522_1_ORAN = $C40F ; 6522 #1 port a data, no handshake
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; right channel
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MOCK_6522_2_ORB = $C480 ; 6522 #2 port b data
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MOCK_6522_2_ORA = $C481 ; 6522 #2 port a data
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MOCK_6522_2_DDRB = $C482 ; 6522 #2 data direction port B
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MOCK_6522_2_DDRA = $C483 ; 6522 #2 data direction port A
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MOCK_6522_2_T1C_L = $C484 ; 6522 #2 Low-order counter
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MOCK_6522_2_T1C_H = $C485 ; 6522 #2 High-order counter
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MOCK_6522_2_T1L_L = $C486 ; 6522 #2 Low-order latch
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MOCK_6522_2_T1L_H = $C487 ; 6522 #2 High-order latch
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MOCK_6522_2_T2C_L = $C488 ; 6522 #2 Timer2 Low-order Latch/Counter
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MOCK_6522_2_T2C_H = $C489 ; 6522 #2 Timer2 High-order Latch/Counter
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MOCK_6522_2_SR = $C48A ; 6522 #2 Shift Register
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MOCK_6522_2_ACR = $C48B ; 6522 #2 Auxiliary Control Register
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MOCK_6522_2_PCR = $C48C ; 6522 #2 Peripheral Control Register
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MOCK_6522_2_IFR = $C48D ; 6522 #2 Interrupt Flag Register
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MOCK_6522_2_IER = $C48E ; 6522 #2 Interrupt Enable Register
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MOCK_6522_2_ORAN = $C48F ; 6522 #2 port a data, no handshake
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;=========================
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; Init Variables
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;=========================
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lda #$0
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sta MB_CHUNK_OFFSET
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;============================
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; Init the Mockingboard
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;============================
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jsr mockingboard_init
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jsr reset_ay_both
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jsr clear_ay_both
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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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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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sei ; disable interrupts just in case
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lda #$40 ; Continuous interrupts, don't touch PB7
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sta MOCK_6522_1_ACR ; ACR register
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lda #$7F ; clear all interrupt flags
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sta MOCK_6522_1_IER ; IER register (interrupt enable)
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lda #$C0
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sta MOCK_6522_1_IFR ; IFR: 1100 0000
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; clear timer interrupt in flag register
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; should we try to clear all?
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sta MOCK_6522_1_IER ; IER: 1100 0000, enable timer1 interrupt
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lda #$E7
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sta MOCK_6522_1_T1C_L ; write into low-order latch
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lda #$4f
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sta MOCK_6522_1_T1C_H ; 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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; 4fe7 / 1e6 = .020s, 50Hz
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;=========================
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; Setup initial conditions
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;=========================
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; 5: C CHANNEL COARSE
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; ldx #5
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; lda #$0 ; always 0
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; sta MB_VALUE
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; jsr write_ay_both
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; 7: ENABLE
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ldx #7
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lda #$38 ; noise disabled, ABC enabled
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sta MB_VALUE
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jsr write_ay_address_right
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; 10: C Amplitude
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ldx #10
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lda #$c ; always volume 12
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sta MB_VALUE
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jsr write_ay_address_right
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; 4: C CHANNEL FINE
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ldx #4
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lda #$51
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sta MB_VALUE
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jsr write_ay_address_right
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;============================
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; Enable 6502 interrupts
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;============================
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cli ; clear interrupt mask
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;============================
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; Loop forever
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;============================
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main_loop:
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jmp main_loop
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;=========
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;routines
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;=========
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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 8 pins output (1), portA
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sta MOCK_6522_1_DDRA
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sta MOCK_6522_2_DDRA
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; only 3 pins output (1), port B
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lda #$7
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sta MOCK_6522_1_DDRB
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sta MOCK_6522_2_DDRB
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rts
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reset_ay_both:
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;======================
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; Reset Left AY-3-8910
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;======================
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reset_ay_left:
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lda #MOCK_AY_RESET
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sta MOCK_6522_1_ORB
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lda #MOCK_AY_INACTIVE
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sta MOCK_6522_1_ORB
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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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lda #MOCK_AY_RESET
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sta MOCK_6522_2_ORB
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lda #MOCK_AY_INACTIVE
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sta MOCK_6522_2_ORB
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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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write_ay_address_left:
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; address
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stx MOCK_6522_1_ORA ; put address on PA1 ; 3
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; on AY-3-8913 hold 300ns
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nop
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lda #MOCK_AY_LATCH_ADDR ; latch_address on PB1 ; 2
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sta MOCK_6522_1_ORB ; latch_address on PB1 ; 3
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nop
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lda #MOCK_AY_INACTIVE ; go inactive ; 2
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sta MOCK_6522_1_ORB ; 3
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; on AY-3-8913 hold at least 50ns
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nop
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write_ay_value_left:
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lda MB_VALUE ; 3
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sta MOCK_6522_1_ORA ; put value on PA1 ; 3
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; AY-3-8913 must hold 50ns
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nop
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lda #MOCK_AY_WRITE ; ; 2
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sta MOCK_6522_1_ORB ; write on PB1 ; 3
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; AY-3-8913 must hold 1800ns
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nop
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nop
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nop
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nop
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nop
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lda #MOCK_AY_INACTIVE ; go inactive ; 2
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sta MOCK_6522_1_ORB ; 3
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; AY-3-8913 must hold 100ns
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nop
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write_ay_address_right:
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; address
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stx MOCK_6522_2_ORA ; put address on PA2 ; 3
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; on AY-3-8913 hold 300ns
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nop
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lda #MOCK_AY_LATCH_ADDR ; latch_address on PB2 ; 2
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sta MOCK_6522_2_ORB ; latch_address on PB2 ; 3
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nop
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lda #MOCK_AY_INACTIVE ; go inactive ; 2
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sta MOCK_6522_2_ORB ; 3
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; on AY-3-8913 hold at least 50ns
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nop
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write_ay_value_right:
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lda MB_VALUE ; 3
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sta MOCK_6522_2_ORA ; put value on PA2 ; 3
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; AY-3-8913 must hold 50ns
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nop
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lda #MOCK_AY_WRITE ; ; 2
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sta MOCK_6522_2_ORB ; write on PB2 ; 3
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; AY-3-8913 must hold 1800ns
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nop
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nop
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nop
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nop
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nop
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lda #MOCK_AY_INACTIVE ; go inactive ; 2
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sta MOCK_6522_2_ORB ; 3
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; AY-3-8913 must hold 100ns
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nop
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rts ; 6
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;===========
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; 53
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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 #13
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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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;================================
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; mockingboard interrupt handler
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;================================
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;================================
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interrupt_handler:
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pha ; save A ; 3
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; Should we save X and Y too?
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bit MOCK_6522_1_T1C_L ; clear 6522 interrupt by
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; reading T1C-L ; 4
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mb_play_music:
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;======================================
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; Write frames to Mockingboard
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;======================================
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; actually plays frame loaded at end of
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; last interrupt, so 20ms behind?
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mb_write_frame:
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ldy MB_CHUNK_OFFSET
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; 4: C CHANNEL FINE
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lda c_fine,Y
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sta MB_VALUE
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ldx #4
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jsr write_ay_value_right
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increment_offset:
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inc MB_CHUNK_OFFSET ; increment offset
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lda MB_CHUNK_OFFSET
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and #$1 ; reduce number played
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; $f = 16
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; $3 = 4
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; $1 = 2
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; $0 = 1
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sta MB_CHUNK_OFFSET
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done_interrupt:
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pla ; restore a ; 4
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rti ; return from interrupt ; 6
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; 4: C fine frequency
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c_fine:
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.byte $51,$3c,$32,$50, $3d,$32,$50,$3c, $33,$50,$3c,$32,$51,$3c,$32,$50
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