192 lines
4.2 KiB
ArmAsm
192 lines
4.2 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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; zp $65-$67 clobbered
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; A/Y clobbered
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;------------------------------------------------------------------------------
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mockingboard_detect:
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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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;===================================================================
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; code to patch mockingboard if not in slot#4
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;===================================================================
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; this is the brute force version, we have to patch 39 locations
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; see further below if you want to try a smaller, more dangerous, patch
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.if 0
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mockingboard_patch:
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lda MB_ADDR_H
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sta pt3_irq_smc1+2 ; 1
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sta pt3_irq_smc2+2 ; 2
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sta pt3_irq_smc2+5 ; 3
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sta pt3_irq_smc3+2 ; 4
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sta pt3_irq_smc3+5 ; 5
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sta pt3_irq_smc4+2 ; 6
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sta pt3_irq_smc4+5 ; 7
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sta pt3_irq_smc5+2 ; 8
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sta pt3_irq_smc5+5 ; 9
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sta pt3_irq_smc6+2 ; 10
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sta pt3_irq_smc6+5 ; 11
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sta pt3_irq_smc7+2 ; 12
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sta pt3_irq_smc7+5 ; 13
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sta mock_init_smc1+2 ; 14
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sta mock_init_smc1+5 ; 15
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sta mock_init_smc2+2 ; 16
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sta mock_init_smc2+5 ; 17
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sta reset_ay_smc1+2 ; 18
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sta reset_ay_smc2+2 ; 19
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sta reset_ay_smc3+2 ; 20
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sta reset_ay_smc4+2 ; 21
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sta write_ay_smc1+2 ; 22
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sta write_ay_smc1+5 ; 23
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sta write_ay_smc2+2 ; 24
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sta write_ay_smc2+5 ; 25
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sta write_ay_smc3+2 ; 26
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sta write_ay_smc3+5 ; 27
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sta write_ay_smc4+2 ; 28
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sta write_ay_smc4+5 ; 29
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sta write_ay_smc5+2 ; 30
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sta write_ay_smc5+5 ; 31
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sta write_ay_smc6+2 ; 32
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sta write_ay_smc6+5 ; 33
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sta setup_irq_smc1+2 ; 34
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sta setup_irq_smc2+2 ; 35
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sta setup_irq_smc3+2 ; 36
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sta setup_irq_smc4+2 ; 37
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sta setup_irq_smc5+2 ; 38
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sta setup_irq_smc6+2 ; 39
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rts
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.endif
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;===================================================================
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; dangerous code to patch mockingboard if not in slot#4
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;===================================================================
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; this code patches any $C4 value to the proper slot# if not slot4
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; this can be dangerous, it might over-write other important values
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; that should be $C4
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; safer ways to do this:
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; only do this if 2 bytes after a LDA/STA/LDX/STX
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; count total and if not 39 then print error message
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mockingboard_patch:
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; from mockingboard_init $1BBF
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; to done_pt3_irq_handler $1D85
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ldx MB_ADDR_H
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ldy #0
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lda #<mockingboard_init
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sta MB_ADDR_L
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lda #>mockingboard_init
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sta MB_ADDR_H
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mb_patch_loop:
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lda (MB_ADDR_L),Y
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cmp #$C4
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bne mb_patch_nomatch
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txa
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sta (MB_ADDR_L),Y
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mb_patch_nomatch:
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inc MB_ADDR_L
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lda MB_ADDR_L
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bne mb_patch_oflo
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inc MB_ADDR_H
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mb_patch_oflo:
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lda MB_ADDR_H
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cmp #>update_pt3_play
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bne mb_patch_loop
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lda MB_ADDR_L
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cmp #<update_pt3_play
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bne mb_patch_loop
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mb_patch_done:
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rts
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