passport/src/patchers/pdi.a
2021-06-21 11:57:02 -04:00

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;-------------------------------
; #PDI
; obfuscated nibble check
; used by Passport Designs, Inc.
;
; tested on
; - Korg-800 4 Track Midi Sequencer
; - MIDI-8 Plus
; - Polywriter
; - Leadsheeter
; - Leadsheeter Utilities
;-------------------------------
!zone {
; gIsDiversi is TRUE here
; (only ever seen this protection on Diversi-DOS disks)
ldy #14
jsr SearchTrack
!byte $A0,$0F ; LDY #$0F
!byte $B9,$00,$00 ; LDA $0000,Y
!byte $99,$E4,$95 ; STA $95E4,Y
!byte $88 ; DEY
!byte $10,$F7 ; BPL *-9
!byte $4C,$E3,$93 ; JMP $93E3
bcs .exit ; passport-test-suite/Polywriter.woz [C=0] matches
jsr PrintByID
!byte s_pdi
jsr inx0C
jsr modify2
!byte $99,$8E ; jmp directly to decoder
.exit
}