;;
  ;;  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/>.
  ;;

wait_new_cmd
  movlw     combuff
  movwf     FSR
  clrf      combuff
  clrf      current_cmdlen
  clrf      flags

wait_cmd
  call      com_rx_byte
  movwf     INDF          ; process received byte
  incf      FSR,f
  btfss     F_CMD_STARTED
  goto      wait_cmd_len
  movf      current_cmdlen,f
  btfsc     STATUS,Z
  goto      new_cmd
  decfsz    current_cmdlen,f
  goto      wait_cmd
  goto      exec_cmd

wait_cmd_len              ; command code received, now wait for length
  bsf       F_CMD_STARTED
  goto      wait_cmd

new_cmd                   ; got new command code and length -> check it
  movf      combuff,w
  sublw     CMD_MAX
  btfss     STATUS,C
  goto      invalid_cmd
  movlw     CMD_MIN_LEN         ; check for minimum command len
  subwf     combuff + .1,w
  btfss     STATUS,C
  goto      invalid_cmd
  movlw     .2                  ; 2 bytes already received
  subwf     combuff + .1,w
  movwf     current_cmdlen
  goto      wait_cmd

exec_cmd                        ; command is complete -> check csum
  movlw     combuff
  movwf     FSR
  movf      combuff + .1,w
  movwf     cnt
  clrf      csum
exec_cmd_check_csum
  movf      INDF,w
  xorwf     csum,f
  incf      FSR,f
  decfsz    cnt,f
  goto      exec_cmd_check_csum
  movf      csum,f
  btfss     STATUS,Z
  goto      csum_error

  movf      combuff,w           ; command is correct and complete -> dispatch
  addwf     PCL,f
  goto      wait_new_cmd
  goto      cmd_identify        ; identify
  goto      cmd_boot            ; boot
  goto      HOOK_CMD_RESET      ; reset
  goto      HOOK_CMD_R_FLASH    ; read flash segment
  goto      HOOK_CMD_W_FLASH    ; write flash segment
  goto      HOOK_CMD_R_EEPROM   ; read eeprom
  goto      HOOK_CMD_W_EEPROM   ; write eeprom
  goto      HOOK_CMD_R_CONFIG   ; read config
  goto      HOOK_CMD_R_CONFIG   ; write config

  ;; ** generic error messages *******
invalid_cmd               ; received command code is not known or len is bogus
  movlw     E_INV_CMD
  call      ack_cmd
  goto      wait_new_cmd

csum_error                 ; received command has an invalid check sum
  movlw     E_BAD_CSUM
  call      ack_cmd
  goto      wait_new_cmd

address_invalid            ; received command uses invalid address (i.e. not aligned to 16bytes)
  movlw     E_ADDR_INVALID
  call      ack_cmd
  goto      wait_new_cmd

address_prohibited         ; received command uses prohibited address (i.e. FLASH < 0x100)
  movlw     E_ADDR_PROHIB
  call      ack_cmd
  goto      wait_new_cmd

  ;; ** generic command handlers ************
  ;; ** identify *******
cmd_identify
  clrf      csum
  movf      combuff,w
  call      com_tx_byte

  movlw     .18
  call      com_tx_byte

  movlw     E_OK
  call      com_tx_byte

  movlw     VERSION_MIN
  call      com_tx_byte
  movlw     VERSION_MAJ
  call      com_tx_byte

  movlw     NAME_0
  call      com_tx_byte
  movlw     NAME_1
  call      com_tx_byte
  movlw     NAME_2
  call      com_tx_byte

  movlw     DEVID_L
  call      com_tx_byte
  movlw     DEVID_H
  call      com_tx_byte

  movlw     FLASH_SIZE_L
  call      com_tx_byte
  movlw     FLASH_SIZE_H
  call      com_tx_byte
  movlw     FSS
  call      com_tx_byte

  movlw     EEPROM_SIZE_L
  call      com_tx_byte
  movlw     EEPROM_SIZE_H
  call      com_tx_byte
  movlw     MESS
  call      com_tx_byte

  movlw     CFG
  call      com_tx_byte

  movf      csum,w
  call      com_tx_byte
  goto      wait_new_cmd

  ;; ** boot *******
cmd_boot
  movlw     E_OK
  call      ack_cmd
  goto      USERVECT

  ;; ** not implemented commands *******
cmd_not_impl
  movlw     E_NOT_IMPL
  call      ack_cmd
  goto      wait_new_cmd