contrib/loaders/erase_check/stm8_erase_check.s

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2
   3 /*
   4  *   Copyright (C) 2017 Ake Rehnman
   5  *   ake.rehnman(at)gmail.com
   6  */
   7 ;;
   8 ;; erase check memory code
   9 ;;
  10  .org 0x0
  11 ;; start address
  12  start_addr: .byte 0x00
  13        .word 0x8000
  14 ;; byte count
  15  byte_cnt: .byte 0x00
  16        .word 0x8000
  17 ;
  18 ; SP must point to start_addr on entry
  19 ; first relocate start_addr to the location
  20 ; we are running at
  21 start:
  22         ldw X,SP
  23         ldw .cont+2,X
  24         ldw X,(start_addr+1,SP) ;start addr
  25         ldw Y,(byte_cnt+1,SP)   ;count
  26         ld A,#0xff
  27 ;
  28 ; if count == 0 return
  29 .L1:
  30         tnzw Y
  31         jrne .decrcnt   ;continue if low word != 0
  32         tnz (byte_cnt,SP)       ;high byte
  33         jreq .exit      ;goto exit
  34 ;
  35 ; decrement count (byte_cnt)
  36 .decrcnt:
  37         tnzw Y  ;low word count
  38         jrne .decr1
  39         dec (byte_cnt,SP)       ;high byte
  40 .decr1:
  41         decw Y; decr low word
  42 ;
  43 ; first check if [start_addr] is 0xff
  44 .cont:
  45         ldf A, [start_addr.e]
  46         cp A,#0xff
  47         jrne .exit ;exit if not 0xff
  48 ;
  49 ; increment start_addr (addr)
  50         incw X
  51         jrne .L1
  52         inc (start_addr,SP)     ;increment high byte
  53         jra .L1
  54 ;
  55 .exit:
  56         ldw (start_addr+1,SP),X ;start addr
  57         ldw (byte_cnt+1,SP),Y   ;count
  58         break