contrib/loaders/checksum/armv7m_crc.s

   1 /***************************************************************************
   2  *   Copyright (C) 2010 by Spencer Oliver                                  *
   3  *   spen@spen-soft.co.uk                                                  *
   4  *                                                                         *
   5  *   This program is free software; you can redistribute it and/or modify  *
   6  *   it under the terms of the GNU General Public License as published by  *
   7  *   the Free Software Foundation; either version 2 of the License, or     *
   8  *   (at your option) any later version.                                   *
   9  *                                                                         *
  10  *   This program is distributed in the hope that it will be useful,       *
  11  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  12  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  13  *   GNU General Public License for more details.                          *
  14  *                                                                         *
  15  *   You should have received a copy of the GNU General Public License     *
  16  *   along with this program; if not, write to the                         *
  17  *   Free Software Foundation, Inc.,                                       *
  18  *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
  19  ***************************************************************************/
  20
  21 /*
  22         parameters:
  23         r0 - address in - crc out
  24         r1 - char count
  25 */
  26
  27         .text
  28         .syntax unified
  29         .cpu cortex-m3
  30         .thumb
  31         .thumb_func
  32
  33         .align  2
  34
  35 _start:
  36 main:
  37         mov             r2, r0
  38         mov             r0, #0xffffffff /* crc */
  39         mov             r3, r1
  40         mov             r4, #0
  41         b               ncomp
  42 nbyte:
  43         ldrb    r1, [r2, r4]
  44
  45         ldr             r7, CRC32XOR
  46         eor             r0, r0, r1, asl #24
  47         mov             r5, #0
  48 loop:
  49         cmp             r0, #0
  50         mov             r6, r0, asl #1
  51         add             r5, r5, #1
  52         mov             r0, r6
  53         it              lt
  54         eorlt   r0, r6, r7
  55         cmp             r5, #8
  56         bne             loop
  57
  58         add             r4, r4, #1
  59 ncomp:
  60         cmp             r4, r3
  61         bne             nbyte
  62         bkpt    #0
  63
  64 CRC32XOR:       .word   0x04c11db7
  65
  66         .end