| /****************************************************************************** ; 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". 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To protect TI''s ; rights in the Program, you agree not to decompile, reverse ; engineer, disassemble or otherwise translate any object code ; versions of the Program to a human-readable form. You agree ; that in no event will you alter, remove or destroy any ; copyright notice included in the Program. TI reserves all ; rights not specifically granted under this license. Except ; as specifically provided herein, nothing in this agreement ; shall be construed as conferring by implication, estoppel, ; or otherwise, upon you, any license or other right under any ; TI patents, copyrights or trade secrets. ; ; You may not use the Program in non-TI devices. ; ;******************************************************************************/ /********************************************************************************** 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__ #include "MSP430x16x.h" #endif #include "..\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 << 8; for(j = 0; j < 8; j++) ptable = (ptable << 1) ^ (ptable & 0x8000 ? poly : 0); } } void crc32BuildTable(unsigned long *ptable, unsigned long poly) { unsigned int i, j; for(i = 0; i <= 255; i++) { ptable = (long)i << 24; for(j = 0; j < 8; j++) ptable = (ptable << 1) ^ (ptable & 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; |
