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MSP430实现循环冗余算法
[ 2006-6-18 14:54:59 | By: 超越梦想 ]
/******************************************************************************
; Code for application report slaa221 - "CRC Implementation with MSP430"
;
; E.Lenchak
; Texas Instruments, Inc
; March 2004
; Built with IAR Embedded Workbench Version: 3.20A
;******************************************************************************
; THIS PROGRAM IS PROVIDED "AS IS". TI MAKES NO WARRANTIES OR
; REPRESENTATIONS, EITHER EXPRESS, IMPLIED OR STATUTORY,
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; YOUR USE OF THE PROGRAM.
;
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; well as other intellectual property laws. To protect TI's
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; that in no event will you alter, remove or destroy any
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;******************************************************************************/
/**********************************************************************************
FUNCTIONS: 16/32-bit CRC Algorithms, bitwsie and table methods
ARGUMENTS: "bitwise algorithm function signature"
return: CRC
arg1: CRC init value
arg2: CRC generator polynomial
arg3: pointer to the message
arg4: size of message in bytes
"table-based algorithm function signature"
return: CRC
arg1: CRC init value
arg2: pointer to CRC table (specific to generator polynomial)
arg3: pointer to the message
arg4: size of message in bytes
***********************************************************************************/
#ifdef __ICC430__
＃i nclude "msp430x16x.h"
#endif
＃i nclude "..\inc\crc.h"
/**************************************
CRC MEMBERS (FUNCTIONS)
**************************************/
// this is an equivalent C implementation to the assembly implementation
unsigned short crc16MakeBitwise(unsigned short crc, unsigned short poly,
unsigned char *pmsg, unsigned int msg_size)
{
unsigned int i, j, carry;
unsigned char msg;
unsigned short temp;
temp = *pmsg++ << 8;
temp |= *pmsg++;
crc ^= temp;
for(i = 0 ; i < msg_size-2 ; i ++)
{
msg = *pmsg++;
for(j = 0 ; j < 8 ; j++)
{
carry = crc & 0x8000;
crc = (crc << 1) | (msg >> 7);
if(carry) crc ^= poly;
msg <<= 1;
}
}
for(i = 0 ; i < 2 ; i ++)
{
for(j = 0 ; j < 8 ; j++)
{
carry = crc & 0x8000;
crc <<= 1;
if(carry) crc ^= poly;
}
}
return(crc ^ CRC16_FINAL_XOR);
}
// this is a C-optimized implementation
unsigned short crc16MakeBitwise2(unsigned short crc, unsigned short poly,
unsigned char *pmsg, unsigned int msg_size)
{
unsigned int i, j;
unsigned short msg;
for(i = 0 ; i < msg_size ; i ++)
{
msg = (*pmsg++ << 8);
for(j = 0 ; j < 8 ; j++)
{
if((msg ^ crc) >> 15) crc = (crc << 1) ^ poly;
else crc <<= 1;
msg <<= 1;
}
}
return(crc ^ CRC16_FINAL_XOR);
}
// this is an equivalent C implementation to the assembly implementation
unsigned long crc32MakeBitwise(unsigned long crc, unsigned long poly,
unsigned char *pmsg, unsigned int msg_size)
{
unsigned int i, j, carry;
unsigned char msg;
unsigned long temp;
temp = (unsigned long)(*pmsg++) << 24;
temp |= (unsigned long)(*pmsg++) << 16;
temp |= (unsigned long)(*pmsg++) << 8;
temp |= (unsigned long)(*pmsg++);
crc ^= temp;
for(i = 0 ; i < msg_size-4 ; i ++)
{
msg = *pmsg++;
for(j = 0 ; j < 8 ; j++)
{
carry = crc >> 31;
crc = (crc << 1) | (msg >> 7);
if(carry) crc ^= poly;
msg <<= 1;
}
}
for(i = 0 ; i < 4 ; i ++)
{
for(j = 0 ; j < 8 ; j++)
{
carry = crc >> 31;
crc <<= 1;
if(carry) crc ^= poly;
}
}
return(crc ^ CRC32_FINAL_XOR);
}
// this is a C-optimized implementation
unsigned long crc32MakeBitwise2(unsigned long crc, unsigned long poly,
unsigned char *pmsg, unsigned int msg_size)
{
unsigned int i, j;
unsigned long msg;
for(i = 0 ; i < msg_size ; i++)
{
msg = *pmsg++;
msg <<= 24;
for(j = 0 ; j < 8 ; j++)
{
if((msg ^ crc) >> 31) crc = (crc << 1) ^ poly;
else crc <<= 1;
msg <<= 1;
}
}
return(crc ^ CRC32_FINAL_XOR);
}
unsigned short crc16MakeTableMethod(unsigned short crc, TBL_MEM unsigned short *table,
unsigned char *pbuffer, unsigned int length)
{
while(length--)
crc = table[((crc >> 8) ^ *pbuffer++)] ^ (crc << 8); // normal
return(crc ^ CRC16_FINAL_XOR);
}
unsigned short crc16rMakeTableMethod(unsigned short crc, TBL_MEM unsigned short *table,
unsigned char *pbuffer, unsigned int length)
{
while(length--)
crc = table[(crc & 0xFF) ^ *pbuffer++] ^ (crc >> 8); // reflected
return(crc ^ CRC16R_FINAL_XOR);
}
unsigned long crc32MakeTableMethod(unsigned long crc, TBL_MEM unsigned long *table,
unsigned char *pbuffer, unsigned int length)
{
while(length--)
crc = table[((crc >> 24) ^ *pbuffer++)] ^ (crc << 8); // normal
return(crc ^ CRC32_FINAL_XOR);
}
unsigned long crc32rMakeTableMethod(unsigned long crc, TBL_MEM unsigned long *table,
unsigned char *pbuffer, unsigned int length)
{
while(length--)
crc = table[(crc ^ *pbuffer++) & 0xFFL] ^ (crc >> 8); // reflected
return(crc ^ CRC32R_FINAL_XOR);
}
/************************************
CRC UTILITIES
************************************/
void crc16BuildTable(unsigned short *ptable, unsigned short poly)
{
unsigned int i, j;
for(i = 0; i <= 255; i++)
{
ptable[i] = i << 8;
for(j = 0; j < 8; j++)
ptable[i] = (ptable[i] << 1) ^ (ptable[i] & 0x8000 ? poly : 0);
}
}
void crc32BuildTable(unsigned long *ptable, unsigned long poly)
{
unsigned int i, j;
for(i = 0; i <= 255; i++)
{
ptable[i] = (long)i << 24;
for(j = 0; j < 8; j++)
ptable[i] = (ptable[i] << 1) ^ (ptable[i] & 0x80000000 ? poly : 0);
}
}
unsigned long bitReflect(unsigned long data, unsigned int width)
{
unsigned long result = 0;
unsigned int i;
for (i = 1; i < (width + 1); i++)
{
if(data & 1) result |= 0x1L << (width - i);
data >>= 1;
}
return result;
}
/************************************ END ***************************************/
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