!**************************************************************************
!*
!* Network driver interface for netboot bootrom
!*
!* Module:  chksum.S
!* Purpose: Routine to compute a checksum
!* Entries: dochecksum
!*
!**************************************************************************
!*
!* Copyright (C) 1998-2003 Gero Kuhlmann <gero@gkminix.han.de>
!*
!*  This program 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 2 of the License, or
!*  any later version.
!*
!*  This program 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 this program; if not, write to the Free Software
!*  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
!*
!* $Id: chksum.S,v 1.4 2003/01/25 23:29:41 gkminix Exp $
!*


!
!**************************************************************************
!
! Load assembler macros and other include files.
!
#include <general.inc>


!
!**************************************************************************
!
! Start code segment.
!
	.text

	public	dochecksum


!
!**************************************************************************
!
! Compute checksum of a given memory area
! Input:  DS:SI  -  pointer to memory area
!         CX     -  size of memory area
! Output: AL     -  checksum
! Registers changed: AX, CX
!
dochecksum:

	cld
	push	si
	xor	ax,ax
chks1:	lodsb
	add	ah,al			! add all bytes together
	loop	chks1
	mov	al,ah
	pop	si
	ret


!
!**************************************************************************
!
	end