;-------------------------------
; IDEA
; identify Electronic Arts custom bootloader
;
; in:    track buffer contains T00,S00
;        A = 0
;        X = 0
; out:   C clear if EA bootloader was found
;        C set if not found
;        A = 0
;        X = 0
;        all other registers & flags clobbered
;
; module by qkumba
;-------------------------------
!macro IDEA {
         ldy   #16
         jsr   compare
         !byte $05,$4C,$04,$08,$A9,$00,$8D,$F2
         !byte $03,$A9,$C6,$8D,$F3,$03,$49,$A5
         bcc   +
         jsr   compare
         !byte $01,$A5,$27,$C9,$09,$D0,$2E,$A2
         !byte $10,$8A,$9D,$EF,$03,$CA,$D0,$F9
+
}

foundea
;
; We found an EA bootloader. Now we create
; an RWTS that can read the rest of the disk.
; Starting with our built-in RWTS, we modify address
; and data prologues based on the parameters of the
; original disk.
;
!zone {
         jsr   PrintByID
         !byte s_eab0
         jsr   CopyUniversal

; mark track $22 as "optional" in sector map

         ldy   #$0F
         lda   #kSectorOptional
.ignoresectors
         sta   T22,y
         dey
         bpl   .ignoresectors

;hook read data prologue
         lda   #<.checktrk
         sta   $BE36
         lda   #>.checktrk
         sta   $BE37

;
; this RWTS alters the data prologue in a routine
; on a non-zero track, so we need to set a flag so
; we know to search for it later
;
         lda   #TRUE
         sta   gIsEA
         jmp   ADStyle

.prologtbl
         !byte $AA, $BB, $AD, $CF

         ;try regular values first

.checktrk
         ldy   #0
         lda   .prologtbl, y
         sta   UNIV_D2
         lda   .prologtbl+2, y
         sta   UNIV_D3
         jsr   $B8DC
         bcc   +

         ;on failure, switch to alternative values
         ;we keep using the last successful values until we fail
         ;and then we switch again

         lda   .checktrk + 1
         eor   #1
         sta   .checktrk + 1

         ;and allow DOS to retry
         ;if DOS runs out of retries, then Passport will report it

+        rts
}