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163 lines
4.1 KiB
ArmAsm
163 lines
4.1 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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; 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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sta MOCK_6522_DDRB1
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sta MOCK_6522_DDRA1
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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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; 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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sta MOCK_6522_ORB1
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lda #MOCK_AY_INACTIVE
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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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lda #MOCK_AY_RESET
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sta MOCK_6522_ORB2
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lda #MOCK_AY_INACTIVE
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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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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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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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lda #MOCK_AY_INACTIVE ; go inactive ; 2
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sta MOCK_6522_ORB1 ; 3
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sta MOCK_6522_ORB2 ; 3
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; value
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lda MB_VALUE ; 3
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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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sta MOCK_6522_ORB1 ; write on PB1 ; 3
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sta MOCK_6522_ORB2 ; write on PB2 ; 3
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lda #MOCK_AY_INACTIVE ; go inactive ; 2
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sta MOCK_6522_ORB1 ; 3
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sta MOCK_6522_ORB2 ; 3
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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 #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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; Detect a Mockingboard card in Slot4
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;=======================================
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; Based on code from the French Touch "Pure Noise" Demo
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; Attempts to time an instruction sequence with a 6522
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;
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; MB_ADDR_L:MB_ADDR_H has address of Mockingboard
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; returns X=0 if not found, X=1 if found
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mockingboard_detect_slot4:
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lda #0
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sta MB_ADDR_L
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mb4_detect_loop: ; self-modifying
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lda #$04 ; we're only looking in Slot 4
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ora #$C0 ; make it start with C
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sta MB_ADDR_H
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ldy #04 ; $CX04
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ldx #02 ; 2 tries?
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mb4_check_cycle_loop:
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lda (MB_ADDR_L),Y ; timer 6522 (Low Order Counter)
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; count down
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sta TEMP ; 3 cycles
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lda (MB_ADDR_L),Y ; + 5 cycles = 8 cycles
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; between the two accesses to the timer
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sec
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sbc TEMP ; subtract to see if we had 8 cycles
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cmp #$f8 ; -8
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bne mb4_not_in_this_slot
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dex ; decrement, try one more time
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bne mb4_check_cycle_loop ; loop detection
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inx ; Mockingboard found (X=1)
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done_mb4_detect:
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rts ; return
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mb4_not_in_this_slot:
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ldx #00
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beq done_mb4_detect
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