;;
  ;;  spreadspace pic utils
  ;;
  ;;
  ;;  Copyright (C) 2011-2013 Christian Pointner <equinox@spreadspace.org>
  ;;
  ;;  This file is part of spreadspace pic utils.
  ;;
  ;;  spreadspace pic utils is free software: you can redistribute it and/or modify
  ;;  it under the terms of the GNU General Public License as published by
  ;;  the Free Software Foundation, either version 3 of the License, or
  ;;  any later version.
  ;;
  ;;  spreadspace pic utils is distributed in the hope that it will be useful,
  ;;  but WITHOUT ANY WARRANTY; without even the implied warranty of
  ;;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  ;;  GNU General Public License for more details.
  ;;
  ;;  You should have received a copy of the GNU General Public License
  ;;  along with spreadspace pic utils. If not, see <http://www.gnu.org/licenses/>.
  ;;

  ;; flash read --------
cmd_reset
  movlw     E_OK
  call      ack_cmd
  movlb     .3
cmd_resset_wait_ack
  btfss     TXSTA,TRMT
  goto      cmd_resset_wait_ack
  reset

  ;; flash read --------
cmd_r_flash
  movlw     FSS                 ; initialize EEADR:EEADRH and FSR
  movwf     cnt
  movlb     .3
  movlw     combuff + .2
  movwf     FSR
  movf      INDF,w
  movwf     EEADRL
  incf      FSR,f
  movf      INDF,w
  movwf     EEADRH
read_flash_segment_loop
  bcf       EECON1,CFGS         ; perform the actual read
  bsf       EECON1,EEPGD
  bsf       EECON1,RD
  nop
  nop
  movf      EEDATL,w            ; load code word from EEDAT:EEDATH to combuff
  movwf     INDF
  incf      FSR,f
  movf      EEDATH,w
  movwf     INDF
  incf      FSR,f
  incfsz    EEADRL,f            ; increment flash address
  goto      read_flash_segment_next
  incf      EEADRH,f
read_flash_segment_next
  decfsz    cnt,f
  goto      read_flash_segment_loop
  movlb     .0
  clrf      combuff + .2  ; = E_OK
  movlw     .1 + .2*FSS   ; bytes to send
  call      send_answer
  goto      wait_new_cmd

  ;; flash write --------
cmd_w_flash
  movlw     .2                     ; if addr[15:8] < 2 -> boot loader section
  subwf     combuff + .3,w
  btfss     STATUS,C
  goto      address_prohibited
  movlw     FLASH_BOUNDARY         ; addr on boundary?
  andwf     combuff + .2,w
  btfss     STATUS,Z
  goto      address_invalid
  movlw     FSS                 ; initialize EEADR:EEADRH and FSR
  movwf     cnt
  movlb     .3
  movlw     combuff + .2
  movwf     FSR
  movf      INDF,w
  movwf     EEADRL
  incf      FSR,f
  movf      INDF,w
  movwf     EEADRH
  bcf       EECON1,CFGS
  bsf       EECON1,EEPGD
  bsf       EECON1,WREN

write_flash_segment_loop
  incf      FSR,f               ; load code word into EEDAT:EEDATH
  movf      INDF,w
  movwf     EEDATL
  incf      FSR,f
  movf      INDF,w
  movwf     EEDATH

  bsf       EECON1,FREE         ; erase row before writing
  movlw     H'55'
  movwf     EECON2
  movlw     H'AA'
  movwf     EECON2
  bsf       EECON1,WR
  nop
  nop
  bcf       EECON1,FREE         ; now start the acutal write sequence
  movf      EEADRL,w
  andlw     FLASH_BOUNDARY
  xorlw     FLASH_BOUNDARY
  btfss     STATUS,Z
  bsf       EECON1,LWLO
  btfsc     STATUS,Z
  bcf       EECON1,LWLO
  movlw     H'55'
  movwf     EECON2
  movlw     H'AA'
  movwf     EECON2
  bsf       EECON1,WR
  nop
  nop
  incfsz    EEADRL,f            ; increment flash address
  goto      write_flash_segment_next
  incf      EEADRH,f
write_flash_segment_next
  decfsz    cnt,f
  goto      write_flash_segment_loop

  bcf       EECON1,WREN
  movlw     E_OK                ; check if a write error occured
  btfsc     EECON1,WRERR
  movlw     E_FLASH_WERR
  movlb     .0
  movwf     combuff + .2  ; = E_OK or write error
  movlw     .1            ; bytes to send
  call      send_answer
  goto      wait_new_cmd

  ;; read config --------
cmd_r_config
  movf      combuff + .2,w
  sublw     CFG - .1
  btfss     STATUS,C
  goto      address_invalid
  movf      combuff + .2,w
  movlb     .3
  addlw     CONFIG_OFFSET
  movwf     EEADRL
  clrf      EEADRH
  bsf       EECON1,CFGS
  bsf       EECON1,RD
  nop
  nop
  movf      EEDATL,w
  movlb     .0
  movwf     combuff + .3
  movlb     .3
  movf      EEDATH,w
  movlb     .0
  movwf     combuff + .4
  movlw     E_OK
  movwf     combuff + .2  ; = E_OK
  movlw     .3            ; bytes to send
  call      send_answer
  goto      wait_new_cmd