gTrack   !byte $00
gSector  !byte $00

gRWTSParams
         !byte $01,$60,$01,$00
_track   !byte $00
_sector  !byte $00
         !word dct
gAddress !word $1F00
         !byte $00,$00
gCommand !byte $01,$00,$FE,$60,$01,$00,$00
dct      !byte $00,$01,$EF,$D8,$00

;-------------------------------
; ReadSector
; high-level function to read a single sector.
; in:  gIsProtDOS is TRUE or FALSE
;      if gProtDOS is FALSE, jCallRWTS has been set to
;        the RWTS entry point (e.g. $BDxx or $3Dxx)
; out: all registers clobbered
;      C clear if read was successful
;      C set if read failed
;-------------------------------
ReadSectorXY
         stx   gTrack
         sty   gSector
ReadSector
;
; Lots of custom RWTS routines need these zero page locations
; set to magic values. Always the same values though!
;
         lda   #$AA
         sta   $31
         lda   #$AD
         sta   $4E
;
; Copy requested track and sector into RWTS parameter table.
; These are maintained outside the table because some disks
; alter the values from inside the RWTS. (MUSE)
;
         lda   gTrack
         sta   _track
         lda   gSector
         sta   _sector

         lda   gIsProtDOS
         beq   _protread
@go
         ldy   #<gRWTSParams
         lda   #>gRWTSParams
         jsr   jCallRWTS
         bcc   +
         lda   gOnAClearDayYouCanReadForever
         beq   @go
+        rts

;
; "Protected.DOS" has enough differences that we just
; split everything out here. The hi/lo RWTS parameter
; table address is set in A/Y instead of Y/A. The
; RWTS entry point is $BA00. The third data prologue
; nibble is stored in zp$4E and varies based on track
; and sector.
;
_protread
         lda   gTrack     ; T02,S05+ use "protected" mode
         cmp   #$03       ; (altered data prologue and
         bcs   @protected ; nibble translate table)
         cmp   #$02       ; T00,S00 - T02,S04 use
         bcc   @standard  ; "standard" mode
         lda   gSector
         cmp   #$05
         bcs   @protected
@standard
         lda   #$9B
         sta   $BF2C
         bne   @go        ; unconditional branch
@protected
         lda   #$B5
         sta   $4E
         lda   #$D5
         sta   $BF2C      ; execution falls through here
@go      lda   #<gRWTSParams
         ldy   #>gRWTSParams
         jsr   $BA00      ; note non-standard entry point
         bcc   +
         lda   gOnAClearDayYouCanReadForever
         beq   @go
+        rts

;-------------------------------
; PreReadSector
; in:  A contains sector map code that specifies what to do
; out: A contains (possibly new) sector map code
;      assume all other things clobbered
;-------------------------------
PreReadSector
         cmp   #kSectorResetAdaptiveRWTS
         beq   @reset
         cmp   #kSectorIgnoreAddressChecksum
         beq   IgnoreAddressChecksum
         cmp   #kSectorCustomDOS32B4BB
         beq   @b4bb
         rts
@reset
         jsr   CopyUniversal
         lda   #kSectorRequired
         rts
@b4bb
         ldx   jCallRWTS+2
         dex
         dex
         dex
         dex
         stx   @a+2
         stx   @b+2
         ldx   #$D5
@a       stx   $FF76
         ldx   #$ED
@b       stx   $FFB2
         rts

IgnoreAddressChecksum
; out: A,Y preserved
;      X clobbered
         ldx   #$00
         stx   $B98A
         rts

;-------------------------------
; ChangeTrack
; in:  A = new track
;-------------------------------
ChangeTrack
         sta   @new+1
         jsr   WriteTrack
@new     lda   #$d1       ; modified at runtime

; note: execution falls through here

ChangeTrackNW             ; "N"o "W"rite
         sta   gTrack
         jsr   ClearTSBuffer
         rts

;-------------------------------
; ChangeSector
; in:  A = new sector
;-------------------------------
ChangeSector
         sta   gSector
         clc
         adc   #BASEPAGE
         sta   gAddress+1
         rts

;-------------------------------
; WriteTrack
; in:    none
;-------------------------------
WriteTrack
         jsr   AnalyzeTrack
WriteTrackNA                         ; entry point used by Special Delivery tracer
                                     ; to write track with 'N'o 'A'nalysis
         bit   gMode
         bpl   @exit                 ; don't write anything in verify mode
         lda   gSaidWriting
         beq   @doTheWriteThing      ; only print 'writing to' message once

         ; we haven't yet printed any 'writing to...' message in the log, so
         ; figure out what that should look like and do it now
         lda   #s_writingto
         jsr   PrintByID

         lda   gHardDiskRef
         beq   @maybeWritingToRAMDisk
         ; we are writing to a file on a hard disk, so print the
         ; full pathname of that file
         jsr   PrintHardDiskImagePath
         bvc   @doneSaidWriting      ; always branches

@maybeWritingToRAMDisk
         lda   gRAMDiskRef
         beq   @notWritingToRAMDisk
         lda   #s_ramdisk            ; writing to (a file on) a RAM disk
         !byte $2C
@notWritingToRAMDisk
         lda   #s_slotanddrive       ; writing to a slot and drive
         jsr   PrintByID

@doneSaidWriting
         lda   #TRUE
         sta   gSaidWriting

@doTheWriteThing
         jsr   SwapProDOS            ; ProDOS out -> in
         jsr   WriteTrackFirstPass
         jsr   SwapProDOS            ; ProDOS in -> out
         bcs   FatalWriteError
@exit    rts

;-------------------------------
; FatalWriteError
; in:    A has MLI error code
; out:   does not return, exits via TheEnd
;-------------------------------
FatalWriteError
         sta   gDisplayBytes
         tax
         lda   #s_writeioerr
         cpx   #MLI_IOERR
         beq   @print
         lda   #s_writenodev
         cpx   #MLI_NODEV
         beq   @print
         lda   #s_writeprot
         cpx   #MLI_WRITEPROT
         beq   @print
         lda   #s_othermli
@print   pha
         lda   #s_writeerr
         jsr   PrintByID
         pla
         jsr   PrintByID
         jmp   TheEnd