223 lines
5.3 KiB
ArmAsm
223 lines
5.3 KiB
ArmAsm
;===================================================================
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; code to detect mockingboard
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;===================================================================
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; this isn't always easy
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; my inclination is to just assume slot #4 but that isn't always realistic
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; code below based on "hw.mockingboard.a" from "Total Replay"
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;license:MIT
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; By Andrew Roughan
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; in the style of 4am for Total Replay
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;
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; Mockingboard support functions
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;
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;------------------------------------------------------------------------------
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; HasMockingboard
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; detect Mockingboard card by searching for 6522 timers across all slots
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; access 6522 timers with deterministic cycle counts
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;
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; based on prior art in Mockingboard Developers Toolkit
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; with optimisation from deater/french touch
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; also takes into account FastChip //e clock difference
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;
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; in: none
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; accelerators should be off
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; out: C set if Mockingboard found in any slot
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; if card was found, X = #$Cn where n is the slot number of the card
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; C clear if no Mockingboard found
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; other flags clobbered
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; A/Y clobbered
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;------------------------------------------------------------------------------
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mockingboard_detect:
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; activate Mockingboard IIc
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; + the Mockingboard has to take over Slot#4 (IIc has no slots)
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; in theory any write to the firmware area in $C400 will
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; activate it, but that might not be fast enough when detecting
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; so writing $FF to $C403/$C404 is official way to enable
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; + Note this disables permanently the mouse firmware in $C400
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; so "normal" interrupts are broken :( The hack to fix things
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; is to switch in RAM for $F000 and just replace the IRQ
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; vectors at $FFFE/$FFFF instead of $3FE/$3FF but that makes
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; it difficult if you actually wanted to use any
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; Applesoft/Monitor ROM routines
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.ifdef PT3_ENABLE_APPLE_IIC
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lda APPLEII_MODEL
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cmp #'C'
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bne not_iic
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lda #$ff
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; don't bother patching these, IIc mockingboard always slot 4
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sta MOCK_6522_DDRA1 ; $C403
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sta MOCK_6522_T1CL ; $C404
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.endif
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not_iic:
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lda #$00
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sta MB_ADDR_L
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ldx #$C7 ; start at slot #7
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mb_slot_loop:
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stx MB_ADDR_H
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ldy #$04 ; 6522 #1 $Cx04
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jsr mb_timer_check
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bne mb_next_slot
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ldy #$84 ; 6522 #2 $Cx84
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jsr mb_timer_check
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bne mb_next_slot
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mb_found:
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sec ; found
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rts
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mb_next_slot:
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dex
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cpx #$C0
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bne mb_slot_loop
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clc ; not found
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rts
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mb_timer_check:
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lda (MB_ADDR_L),Y ; read 6522 timer low byte
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sta MB_VALUE
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lda (MB_ADDR_L),Y ; second time
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sec
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sbc MB_VALUE
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cmp #$F8 ; looking for (-)8 cycles between reads
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beq mb_timer_check_done
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cmp #$F7 ; FastChip //e clock is different
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mb_timer_check_done:
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rts
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.if 0
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;=======================================
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; Detect a Mockingboard card
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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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; If found, puts in bMB
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; MB_ADDRL:MB_ADDRH has address of Mockingboard
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; returns X=0 if not found, X=1 if found
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mockingboard_detect:
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lda #0
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sta MB_ADDRL
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mb_detect_loop: ; self-modifying
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lda #$07 ; we start in slot 7 ($C7) and go down to 0 ($C0)
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ora #$C0 ; make it start with C
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sta MB_ADDRH
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ldy #04 ; $CX04
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ldx #02 ; 2 tries?
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mb_check_cycle_loop:
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lda (MB_ADDRL),Y ; timer 6522 (Low Order Counter)
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; count down
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sta PT3_TEMP ; 3 cycles
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lda (MB_ADDRL),Y ; + 5 cycles = 8 cycles
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; between the two accesses to the timer
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sec
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sbc PT3_TEMP ; subtract to see if we had 8 cycles
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cmp #$f8 ; -8
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bne mb_not_in_this_slot
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dex ; decrement, try one more time
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bne mb_check_cycle_loop ; loop detection
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inx ; Mockingboard found (X=1)
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done_mb_detect:
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;stx bMB ; store result to bMB
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rts ; return
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mb_not_in_this_slot:
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dec mb_detect_loop+1 ; decrement the "slot" (self_modify)
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bne mb_detect_loop ; loop down to one
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ldx #00
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beq done_mb_detect
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;alternative MB detection from Nox Archaist
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; lda #$04
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; sta MB_ADDRL
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; ldx #$c7
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;
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;find_mb:
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; stx MB_ADDRH
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;
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; ;detect sound I
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;
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; sec
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; ldy #$00
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; lda (MB_ADDRL), y
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; sbc (MB_ADDRL), y
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; cmp #$05
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; beq found_mb
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; dex
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; cpx #$c0
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; bne find_mb
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; ldx #$00 ;no mockingboard found
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; rts
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;
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;found_mb:
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; ldx #$01 ;mockingboard found
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; rts
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;
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; ;optionally detect sound II
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;
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; sec
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; ldy #$80
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; lda (MB_ADDRL), y
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; sbc (MB_ADDRL), y
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; cmp #$05
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; beq found_mb
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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_ADDRL:MB_ADDRH 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_ADDRL
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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_ADDRH
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ldy #04 ; $CX04
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ldx #02 ; 2 tries?
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mb4_check_cycle_loop:
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lda (MB_ADDRL),Y ; timer 6522 (Low Order Counter)
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; count down
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sta PT3_TEMP ; 3 cycles
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lda (MB_ADDRL),Y ; + 5 cycles = 8 cycles
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; between the two accesses to the timer
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sec
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sbc PT3_TEMP ; subtract to see if we had 8 cycles
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cmp #$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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.endif
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