; /!\ execution falls through here from Trace
;-------------------------------
; UseUniversal
; Caller has decided to use the built-in RWTS to read
; this disk (possibly already patched with disk-specific
; parameters). Now we check for protections that require
; additional patches or callbacks before we start.
;
; in:    $0800..$08FF contains boot0
;        $B600..$BFFF contains boot1
; out:   all registers clobbered
;        exits via ReadWithRWTS
;-------------------------------
UseUniversal
;
; Copy built-in RWTS into place ($B800..$BFFF)
;
         jsr   StartWithUniv
;
; On pure 13-sector disks, we just hijack the read routine to perform a
; verification instead.
;
         lda   gIs13Sector
         bne   @not13Sector
         lda   #0
         sta   $47E                  ; restore track number replaced by DOS
         lda   #<seekread13
         sta   jCallRWTS+1
         lda   #>seekread13
         sta   jCallRWTS+2
         bne   @doneUnivPatching     ; always branches
@not13Sector
;
; On disks that use the universal RWTS for the entire disk, we use
; an adaptive RWTS that accepts any epilogue on the first sector but then
; enforces all other sectors to have the same epilogue.
;
         ldy   #$09
-        lda   _adaptiveAddressEpilogue, y
         sta   $B994, y
         lda   _adaptiveDataEpilogue, y
         sta   $B938, y
         dey
         bpl   -
;
; On Dinkey-DOS disks (e.g. Ultima V, Times of Lore), we don't use the
; adaptive RWTS we just copied into place. Instead, we use the same space
; to create a hybrid RWTS that alters the sector number in the
; address field based on the address epilogue. Once we normalize the
; sector numbers, no further patches are required, since the RWTS can also
; read unprotected disks. A separate patcher finds the actual code that
; alters the sector number to print it to the log.
;
         lda   gIsDinkeyDOS
         bne   @notDinkeyDOS
         ldy   #$0F
-        lda   _originAddressEpilogue, y
         sta   $B990, y
         lda   _originDataEpilogue, y
         sta   $B92F, y
         dey
         bpl   -
@notDinkeyDOS
;
; On TSR disks (e.g. Dawn Patrol, Dungeon), we start with the universal
; RWTS then apply a patch in memory.
;
         lda   gIsTSR
         bne   @notTSR
         lda   #<_tsrCallback
         sta   $BE8C
         lda   #>_tsrCallback
         sta   $BE8D
@notTSR
;
; Disable drive recalibration on bad sectors so we give up on bad sectors
; faster and detect unformatted or specially structured tracks faster.
;
         lda   #$B0
         sta   $BDD2
         lda   #$30
         sta   $BDD3
;
; Some disks have different epilogues on track 0, so we stop using the
; adaptive RWTS so we don't falsely accuse those disks of being damaged.
; (This is implemented by recopying the entire built-in RWTS into place
; which wipes out all the above patches, but track 0 of Dinkey-DOS and
; TSR disks is readable, so it's OK that they fall through to here.)
;
         lda   #kSectorResetAdaptiveRWTS
         sta   T00S0F
;
; Some disks have an intentionally invalid checksum on T00,S00 (read by
; the drive firmware, which doesn't verify it).
;
         lda   #kSectorIgnoreAddressChecksum
         sta   T00S00
@doneUnivPatching
         jmp   ReadWithRWTS

SwitchToUniv
         lda   gSector
         sta   gDisplayBytes
         lda   #s_switch
         !byte $2C        ; hide next LDA
         ; /!\ execution falls through here

StartWithUniv
         lda   #s_builtin
         sta   +
         jsr   PrintByID
+        !byte $FD                   ; SMC
         lda   #TRUE
         sta   gTriedUniv
         lda   #FALSE
         sta   gIsProtDOS
         ; /!\ execution falls through here

CopyUniversal
         lda   #$B8
         pha
         jsr   MoveT00PakLow         ; move T00 modules out of the way if necessary
         pla
         ; /!\ execution falls through here

CopyUniversalAnywhere
         sta   universalrwts
         clc
         adc   #$02
         sta   .cu+2
         lda   #>universalrwts
         sta   _byte_hi
         lda   #<universalrwts
         sta   _byte_lo
         jsr   decrunch
         sty   jCallRWTS+1
         lda   #$BD
         sta   jCallRWTS+2
         ldy   #$96
.culoop  lda   gNIBTable,y
.cu      sta   $d100,y    ; set at runtime
         iny
         bne   .culoop
         rts

_adaptiveAddressEpilogue  ; to $B994
         !byte $8D,$91,$B9
         !byte $A9,$AE
         !byte $8D,$93,$B9
         !byte $D0,$00

_adaptiveDataEpilogue     ; to $B938
         !byte $8D,$35,$B9
         !byte $A9,$0A
         !byte $8D,$37,$B9
         !byte $18
         !byte $60

_originAddressEpilogue    ; to $B990
         !byte $C9,$AB
         !byte $D0,$0A
         !byte $EA
         !byte $BD,$8C,$C0
         !byte $C9,$AB
         !byte $F0,$95
         !byte $D0,$00
         !byte $18,$60

_originDataEpilogue       ; to $B92F
         !byte $18
         !byte $60
         !byte $38
         !byte $A5,$2D
         !byte $E9,$11
         !byte $85,$2D
         !byte $18
         !byte $60
         ; next 5 bytes are also copied into $B93A..$B93E
         ; which is harmless

_tsrCallback
         pha
         ldy   gTrack
         cpy   #$05
         bcc   @normal
         lda   $F800, y
         and   #$42
         bne   +
         lda   #$42
+        ora   #$B5
         !byte $2C
@normal  lda   #$AD
         sta   $B8FC
         pla
         jmp   $B9A0