ftphelper.a65

; vim: set expandtab shiftwidth=2 tabstop=2:

;  Little helper routine for speeding up mega65_ftp
;  Basically it checks if the sector data provided matches what is on the
;  SD-card at the correct address. If it matches, then it doesn't write anything.
;  If it doesn't match, then it tries to write it, and indicates if the write
;  was successful.
;  To further help things along, we support bulk writing of sectors in this way.
;  This is really just to reduce the turn-around time of commanding via the serial
;  interface all the time

  ; Sector data starts here.
  .alias sector_data $0900

  ; 32-bit sector number
  .alias sector_number $0f00

  ; Single byte count of sectors
  .alias sector_count $0f04

  ; Handshaking addresses
  .alias job_done $0f05          ; set non-zero when done.
  .alias sectors_written $0f06   ; set to count of sectors successfully written

  .org $0c00

entry:

  sei

  inc $0800

  ; Fast CPU
  lda #65
  sta $0

  ; M65 IO
  lda #$47
  sta $D02f
  lda #$53
  sta $D02f

  ; Disable funny memory maps
  LDA #$00
  TAX
  TAY
  TAZ
  MAP
  EOM

  ; setup pointer to sector data
  lda #<sector_data
  sta $fd
  lda #>sector_data
  sta $fe

  ; Map sector buffer at $DE00-$DFFF

  ; Clear colour RAM at $DC00 flag, as this prevents mapping of sector buffer at $DE00
  lda #$01
  TRB $D030

  ; Actually map the sector buffer
  lda #$81
  sta $D680

  ; Set first sector address
  lda sector_number+0
  sta $d681
  lda sector_number+1
  sta $d682
  lda sector_number+2
  sta $d683
  lda sector_number+3
  sta $d684

sector_loop:
  ; Read sector
  lda #$02
  sta $d680

cardbusy:
  lda $d680
  and #$03
  bne cardbusy

  ; Assume read is complete.
  ; Verify sector
  ldy #$00

  lda #<sector_data
  sta $fd
  lda #>sector_data
  sta $fe
vloop1:
  lda $de00,y
  cmp ($fd),y
  bne vfail
  iny
  bne vloop1
vloop2:
  lda $df00,y
  cmp ($fd),y
  bne vfail
  iny
  bne vloop2


  jmp verifyok

vfail:
  ; Verify failed, so write sector

  lda #<sector_data
  sta $fd
  lda #>sector_data
  sta $fe

cloop1:
  lda ($fd),y
  sta $de00,y
  iny
  bne cloop1
cloop2: inc $fe
  lda ($fd),y
  sta $df00,y
  iny
  bne cloop2
  dec $fe

  lda #$03
  sta $d680

  ; Wait for write to complete
cardbusy2:
  inc $d021
  lda $d680
  and #$03
  bne cardbusy2

  lda #$00
  sta $d021

  jmp sector_loop


verifyok:
  inc sectors_written

  ; Advance to next sector
  lda $fe
  clc
  adc #$02

  ; If there are more to do, continue
  dec sector_count
  bne sector_loop

  ; Done
  lda #$01
  sta job_done
endloop:
  inc $d020
  jmp endloop

  .outfile "libexec/ftphelper.bin"