dos33fsprogs/another_myst/pt3_lib_mockingboard_detect.s

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2020-06-20 18:48:19 +00:00
;===================================================================
; code to detect mockingboard
;===================================================================
; this isn't always easy
; my inclination is to just assume slot #4 but that isn't always realistic
; code below based on "hw.mockingboard.a" from "Total Replay"
;license:MIT
; By Andrew Roughan
; in the style of 4am for Total Replay
;
; Mockingboard support functions
;
;------------------------------------------------------------------------------
; HasMockingboard
; detect Mockingboard card by searching for 6522 timers across all slots
; access 6522 timers with deterministic cycle counts
;
; based on prior art in Mockingboard Developers Toolkit
; with optimisation from deater/french touch
; also takes into account FastChip //e clock difference
;
; in: none
; accelerators should be off
; out: C set if Mockingboard found in any slot
; if card was found, X = #$Cn where n is the slot number of the card
; C clear if no Mockingboard found
; other flags clobbered
; zp $65-$67 clobbered
; A/Y clobbered
;------------------------------------------------------------------------------
mockingboard_detect:
lda #$00
sta MB_ADDR_L
ldx #$C7 ; start at slot #7
mb_slot_loop:
stx MB_ADDR_H
ldy #$04 ; 6522 #1 $Cx04
jsr mb_timer_check
bne mb_next_slot
ldy #$84 ; 6522 #2 $Cx84
jsr mb_timer_check
bne mb_next_slot
mb_found:
sec ; found
rts
mb_next_slot:
dex
cpx #$C0
bne mb_slot_loop
clc ; not found
rts
mb_timer_check:
lda (MB_ADDR_L),Y ; read 6522 timer low byte
sta MB_VALUE
lda (MB_ADDR_L),Y ; second time
sec
sbc MB_VALUE
cmp #$F8 ; looking for (-)8 cycles between reads
beq mb_timer_check_done
cmp #$F7 ; FastChip //e clock is different
mb_timer_check_done:
rts
;===================================================================
; code to patch mockingboard if not in slot#4
;===================================================================
; this is the brute force version, we have to patch 39 locations
; see further below if you want to try a smaller, more dangerous, patch
.if 0
mockingboard_patch:
lda MB_ADDR_H
sta pt3_irq_smc1+2 ; 1
sta pt3_irq_smc2+2 ; 2
sta pt3_irq_smc2+5 ; 3
sta pt3_irq_smc3+2 ; 4
sta pt3_irq_smc3+5 ; 5
sta pt3_irq_smc4+2 ; 6
sta pt3_irq_smc4+5 ; 7
sta pt3_irq_smc5+2 ; 8
sta pt3_irq_smc5+5 ; 9
sta pt3_irq_smc6+2 ; 10
sta pt3_irq_smc6+5 ; 11
sta pt3_irq_smc7+2 ; 12
sta pt3_irq_smc7+5 ; 13
sta mock_init_smc1+2 ; 14
sta mock_init_smc1+5 ; 15
sta mock_init_smc2+2 ; 16
sta mock_init_smc2+5 ; 17
sta reset_ay_smc1+2 ; 18
sta reset_ay_smc2+2 ; 19
sta reset_ay_smc3+2 ; 20
sta reset_ay_smc4+2 ; 21
sta write_ay_smc1+2 ; 22
sta write_ay_smc1+5 ; 23
sta write_ay_smc2+2 ; 24
sta write_ay_smc2+5 ; 25
sta write_ay_smc3+2 ; 26
sta write_ay_smc3+5 ; 27
sta write_ay_smc4+2 ; 28
sta write_ay_smc4+5 ; 29
sta write_ay_smc5+2 ; 30
sta write_ay_smc5+5 ; 31
sta write_ay_smc6+2 ; 32
sta write_ay_smc6+5 ; 33
sta setup_irq_smc1+2 ; 34
sta setup_irq_smc2+2 ; 35
sta setup_irq_smc3+2 ; 36
sta setup_irq_smc4+2 ; 37
sta setup_irq_smc5+2 ; 38
sta setup_irq_smc6+2 ; 39
rts
.endif
;===================================================================
; dangerous code to patch mockingboard if not in slot#4
;===================================================================
; this code patches any $C4 value to the proper slot# if not slot4
; this can be dangerous, it might over-write other important values
; that should be $C4
; safer ways to do this:
; only do this if 2 bytes after a LDA/STA/LDX/STX
; count total and if not 39 then print error message
mockingboard_patch:
; from mockingboard_init $1BBF
; to done_pt3_irq_handler $1D85
ldx MB_ADDR_H
ldy #0
lda #<mockingboard_init
sta MB_ADDR_L
lda #>mockingboard_init
sta MB_ADDR_H
mb_patch_loop:
lda (MB_ADDR_L),Y
cmp #$C4
bne mb_patch_nomatch
txa
sta (MB_ADDR_L),Y
mb_patch_nomatch:
inc MB_ADDR_L
lda MB_ADDR_L
bne mb_patch_oflo
inc MB_ADDR_H
mb_patch_oflo:
lda MB_ADDR_H
cmp #>done_pt3_irq_handler
bne mb_patch_loop
lda MB_ADDR_L
cmp #<done_pt3_irq_handler
bne mb_patch_loop
mb_patch_done:
rts
.if 0
;=======================================
; Detect a Mockingboard card
;=======================================
; Based on code from the French Touch "Pure Noise" Demo
; Attempts to time an instruction sequence with a 6522
;
; If found, puts in bMB
; MB_ADDRL:MB_ADDRH has address of Mockingboard
; returns X=0 if not found, X=1 if found
mockingboard_detect:
lda #0
sta MB_ADDRL
mb_detect_loop: ; self-modifying
lda #$07 ; we start in slot 7 ($C7) and go down to 0 ($C0)
ora #$C0 ; make it start with C
sta MB_ADDRH
ldy #04 ; $CX04
ldx #02 ; 2 tries?
mb_check_cycle_loop:
lda (MB_ADDRL),Y ; timer 6522 (Low Order Counter)
; count down
sta PT3_TEMP ; 3 cycles
lda (MB_ADDRL),Y ; + 5 cycles = 8 cycles
; between the two accesses to the timer
sec
sbc PT3_TEMP ; subtract to see if we had 8 cycles
cmp #$f8 ; -8
bne mb_not_in_this_slot
dex ; decrement, try one more time
bne mb_check_cycle_loop ; loop detection
inx ; Mockingboard found (X=1)
done_mb_detect:
;stx bMB ; store result to bMB
rts ; return
mb_not_in_this_slot:
dec mb_detect_loop+1 ; decrement the "slot" (self_modify)
bne mb_detect_loop ; loop down to one
ldx #00
beq done_mb_detect
;alternative MB detection from Nox Archaist
; lda #$04
; sta MB_ADDRL
; ldx #$c7
;
;find_mb:
; stx MB_ADDRH
;
; ;detect sound I
;
; sec
; ldy #$00
; lda (MB_ADDRL), y
; sbc (MB_ADDRL), y
; cmp #$05
; beq found_mb
; dex
; cpx #$c0
; bne find_mb
; ldx #$00 ;no mockingboard found
; rts
;
;found_mb:
; ldx #$01 ;mockingboard found
; rts
;
; ;optionally detect sound II
;
; sec
; ldy #$80
; lda (MB_ADDRL), y
; sbc (MB_ADDRL), y
; cmp #$05
; beq found_mb
;=======================================
; Detect a Mockingboard card in Slot4
;=======================================
; Based on code from the French Touch "Pure Noise" Demo
; Attempts to time an instruction sequence with a 6522
;
; MB_ADDRL:MB_ADDRH has address of Mockingboard
; returns X=0 if not found, X=1 if found
mockingboard_detect_slot4:
lda #0
sta MB_ADDRL
mb4_detect_loop: ; self-modifying
lda #$04 ; we're only looking in Slot 4
ora #$C0 ; make it start with C
sta MB_ADDRH
ldy #04 ; $CX04
ldx #02 ; 2 tries?
mb4_check_cycle_loop:
lda (MB_ADDRL),Y ; timer 6522 (Low Order Counter)
; count down
sta PT3_TEMP ; 3 cycles
lda (MB_ADDRL),Y ; + 5 cycles = 8 cycles
; between the two accesses to the timer
sec
sbc PT3_TEMP ; subtract to see if we had 8 cycles
cmp #$f8 ; -8
bne mb4_not_in_this_slot
dex ; decrement, try one more time
bne mb4_check_cycle_loop ; loop detection
inx ; Mockingboard found (X=1)
done_mb4_detect:
rts ; return
mb4_not_in_this_slot:
ldx #00
beq done_mb4_detect
.endif