dos33fsprogs/demos/second/pt3_lib_mockingboard_patch.s

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2023-08-15 16:53:05 +00:00
;===================================================================
; 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:
; 16-bit increment
inc 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:
stx MB_ADDR_H ; restore slot for later
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rts