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发表于 2013-1-6 21:55:29
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/* Copyright (c) 2002, 2003, 2004 Marek Michalkiewicz
Copyright (c) 2005, Joerg Wunsch
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
* Neither the name of the copyright holders nor the names of
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE. */
/* $Id: crc16.h,v 1.2.2.1 2006/04/19 20:35:54 joerg_wunsch Exp $ */
#ifndef _UTIL_CRC16_H_
#define _UTIL_CRC16_H_
#include <stdint.h>
/** \defgroup util_crc <util/crc16.h>: CRC Computations
\code#include <util/crc16.h>\endcode
This header file provides a optimized inline functions for calculating
cyclic redundancy checks (CRC) using common polynomials.
\par References:
\par
See the Dallas Semiconductor app note 27 for 8051 assembler example and
general CRC optimization suggestions. The table on the last page of the
app note is the key to understanding these implementations.
\par
Jack Crenshaw's "Implementing CRCs" article in the January 1992 isue of \e
Embedded \e Systems \e Programming. This may be difficult to find, but it
explains CRC's in very clear and concise terms. Well worth the effort to
obtain a copy.
A typical application would look like:
\code
// Dallas iButton test vector.
uint8_t serno[] = { 0x02, 0x1c, 0xb8, 0x01, 0, 0, 0, 0xa2 };
int
checkcrc(void)
{
uint8_t crc = 0, i;
for (i = 0; i < sizeof serno / sizeof serno[0]; i++)
crc = _crc_ibutton_update(crc, serno);
return crc; // must be 0
}
\endcode
*/
/** \ingroup util_crc
Optimized CRC-16 calculation.
Polynomial: x^16 + x^15 + x^2 + 1 (0xa001)<br>
Initial value: 0xffff
This CRC is normally used in disk-drive controllers.
The following is the equivalent functionality written in C.
\code
uint16_t
crc16_update(uint16_t crc, uint8_t a)
{
int i;
crc ^= a;
for (i = 0; i < 8; ++i)
{
if (crc & 1)
crc = (crc >> 1) ^ 0xA001;
else
crc = (crc >> 1);
}
return crc;
}
\endcode */
static __inline__ uint16_t
_crc16_update(uint16_t __crc, uint8_t __data)
{
uint8_t __tmp;
uint16_t __ret;
__asm__ __volatile__ (
"eor %A0,%2" "\n\t"
"mov %1,%A0" "\n\t"
"swap %1" "\n\t"
"eor %1,%A0" "\n\t"
"mov __tmp_reg__,%1" "\n\t"
"lsr %1" "\n\t"
"lsr %1" "\n\t"
"eor %1,__tmp_reg__" "\n\t"
"mov __tmp_reg__,%1" "\n\t"
"lsr %1" "\n\t"
"eor %1,__tmp_reg__" "\n\t"
"andi %1,0x07" "\n\t"
"mov __tmp_reg__,%A0" "\n\t"
"mov %A0,%B0" "\n\t"
"lsr %1" "\n\t"
"ror __tmp_reg__" "\n\t"
"ror %1" "\n\t"
"mov %B0,__tmp_reg__" "\n\t"
"eor %A0,%1" "\n\t"
"lsr __tmp_reg__" "\n\t"
"ror %1" "\n\t"
"eor %B0,__tmp_reg__" "\n\t"
"eor %A0,%1"
: "=r" (__ret), "=d" (__tmp)
: "r" (__data), "0" (__crc)
: "r0"
);
return __ret;
}
/** \ingroup util_crc
Optimized CRC-XMODEM calculation.
Polynomial: x^16 + x^12 + x^5 + 1 (0x1021)<br>
Initial value: 0x0
This is the CRC used by the Xmodem-CRC protocol.
The following is the equivalent functionality written in C.
\code
uint16_t
crc_xmodem_update (uint16_t crc, uint8_t data)
{
int i;
crc = crc ^ ((uint16_t)data << 8);
for (i=0; i<8; i++)
{
if (crc & 0x8000)
crc = (crc << 1) ^ 0x1021;
else
crc <<= 1;
}
return crc;
}
\endcode */
static __inline__ uint16_t
_crc_xmodem_update(uint16_t __crc, uint8_t __data)
{
uint16_t __ret; /* %B0:%A0 (alias for __crc) */
uint8_t __tmp1; /* %1 */
uint8_t __tmp2; /* %2 */
/* %3 __data */
__asm__ __volatile__ (
"eor %B0,%3" "\n\t" /* crc.hi ^ data */
"mov __tmp_reg__,%B0" "\n\t"
"swap __tmp_reg__" "\n\t" /* swap(crc.hi ^ data) */
/* Calculate the ret.lo of the CRC. */
"mov %1,__tmp_reg__" "\n\t"
"andi %1,0x0f" "\n\t"
"eor %1,%B0" "\n\t"
"mov %2,%B0" "\n\t"
"eor %2,__tmp_reg__" "\n\t"
"lsl %2" "\n\t"
"andi %2,0xe0" "\n\t"
"eor %1,%2" "\n\t" /* __tmp1 is now ret.lo. */
/* Calculate the ret.hi of the CRC. */
"mov %2,__tmp_reg__" "\n\t"
"eor %2,%B0" "\n\t"
"andi %2,0xf0" "\n\t"
"lsr %2" "\n\t"
"mov __tmp_reg__,%B0" "\n\t"
"lsl __tmp_reg__" "\n\t"
"rol %2" "\n\t"
"lsr %B0" "\n\t"
"lsr %B0" "\n\t"
"lsr %B0" "\n\t"
"andi %B0,0x1f" "\n\t"
"eor %B0,%2" "\n\t"
"eor %B0,%A0" "\n\t" /* ret.hi is now ready. */
"mov %A0,%1" "\n\t" /* ret.lo is now ready. */
: "=d" (__ret), "=d" (__tmp1), "=d" (__tmp2)
: "r" (__data), "0" (__crc)
: "r0"
);
return __ret;
}
/** \ingroup util_crc
Optimized CRC-CCITT calculation.
Polynomial: x^16 + x^12 + x^5 + 1 (0x8408)<br>
Initial value: 0xffff
This is the CRC used by PPP and IrDA.
See RFC1171 (PPP protocol) and IrDA IrLAP 1.1
\note Although the CCITT polynomial is the same as that used by the Xmodem
protocol, they are quite different. The difference is in how the bits are
shifted through the alorgithm. Xmodem shifts the MSB of the CRC and the
input first, while CCITT shifts the LSB of the CRC and the input first.
The following is the equivalent functionality written in C.
\code
uint16_t
crc_ccitt_update (uint16_t crc, uint8_t data)
{
data ^= lo8 (crc);
data ^= data << 4;
return ((((uint16_t)data << 8) | hi8 (crc)) ^ (uint8_t)(data >> 4)
^ ((uint16_t)data << 3));
}
\endcode */
static __inline__ uint16_t
_crc_ccitt_update (uint16_t __crc, uint8_t __data)
{
uint16_t __ret;
__asm__ __volatile__ (
"eor %A0,%1" "\n\t"
"mov __tmp_reg__,%A0" "\n\t"
"swap %A0" "\n\t"
"andi %A0,0xf0" "\n\t"
"eor %A0,__tmp_reg__" "\n\t"
"mov __tmp_reg__,%B0" "\n\t"
"mov %B0,%A0" "\n\t"
"swap %A0" "\n\t"
"andi %A0,0x0f" "\n\t"
"eor __tmp_reg__,%A0" "\n\t"
"lsr %A0" "\n\t"
"eor %B0,%A0" "\n\t"
"eor %A0,%B0" "\n\t"
"lsl %A0" "\n\t"
"lsl %A0" "\n\t"
"lsl %A0" "\n\t"
"eor %A0,__tmp_reg__"
: "=d" (__ret)
: "r" (__data), "0" (__crc)
: "r0"
);
return __ret;
}
/** \ingroup util_crc
Optimized Dallas (now Maxim) iButton 8-bit CRC calculation.
Polynomial: x^8 + x^5 + x^4 + 1 (0x8C)<br>
Initial value: 0x0
See http://www.maxim-ic.com/appnotes.cfm/appnote_number/27
The following is the equivalent functionality written in C.
\code
uint8_t
_crc_ibutton_update(uint8_t crc, uint8_t data)
{
uint8_t i;
crc = crc ^ data;
for (i = 0; i < 8; i++)
{
if (crc & 0x01)
crc = (crc >> 1) ^ 0x8C;
else
crc >>= 1;
}
return crc;
}
\endcode
*/
static __inline__ uint8_t
_crc_ibutton_update(uint8_t __crc, uint8_t __data)
{
uint8_t __i, __pattern;
__asm__ __volatile__ (
" eor %0, %4" "\n\t"
" ldi %1, 8" "\n\t"
" ldi %2, 0x8C" "\n\t"
"1: bst %0, 0" "\n\t"
" lsr %0" "\n\t"
" brtc 2f" "\n\t"
" eor %0, %2" "\n\t"
"2: dec %1" "\n\t"
" brne 1b" "\n\t"
: "=r" (__crc), "=d" (__i), "=d" (__pattern)
: "0" (__crc), "r" (__data));
return __crc;
}
#endif /* _UTIL_CRC16_H_ */
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