smallcrc8.c

ti-Chipcon CC1010 1G以下Soc源码库。包括rf,powermodes,clockmodes,flashRW,interrupts,timer,pwm,uart...所有底层驱动源码

/*****************************************************************************
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 *      ***        ***                                                       *
 *      ***   +++   ***                                                      *
 *      ***   + +   ***                                                      *
 *      ***   +                            CHIPCON CC1010                    *
 *      ***   + +   ***                     CUL - smallcrc                   *
 *      ***   +++   ***                                                      *
 *      ***       ***                                                        *
 *       ***********                                                         *
 *        *********                                                          *
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 * Author:              JOL                                                  *
 *****************************************************************************
 * Revision history:                                                         *
 *                                                                           *
 * $Log: smallcrc8.c,v $
 * Revision 1.1  2002/10/14 12:26:12  tos
 * Initial version in CVS.
 *
 *                                                                           *
 ****************************************************************************/

#include <chipcon/cul.h>


//----------------------------------------------------------------------------
//	byte culSmallCRC8(...)
//
//	Description:
//		A CRC-8 (DOW) implementation optimized for small code size.
//		The function should be called once for each byte in the data
//		the CRC is to be performed on. For the invocation on the first byte
//		the value CRC8_INIT should be given for _crcReg_. The value returned
//		is the CRC-8 of the data supplied so far. This CRC-value should be
//		added at the end of the data to facilitate a later CRC check. During
//		checking the check should be performed on all the data AND the CRC-16
//		value appended to it. The data is intact if the value returned is 0.
//
//	Arguments:
//		byte crcData
//			The data to perform the CRC-8 operation on.
//		byte crcReg
//			The current value of the CRC register. For the first byte the
//			value CRC8_INIT should be supplied. For each additional byte the
//			value returned for the last invocation should be supplied.
//
//	Return value:
//		The updated value of the CRC8 register. This corresponds to the 
//		CRC-8 of the data supplied so far. During CRC checking, after working
//		through all the data and the appended CRC-8 value, the value will be
//		0 if the data is intact.
//----------------------------------------------------------------------------
byte culSmallCRC8(byte crcData, byte crcReg) {
	byte i;

	for (i = 0; i < 8; i++) {
		if ((crcReg & 0x80) ^ (crcData & 0x80))
			crcReg = (crcReg << 1) ^  CRC8_POLY;
		else
			crcReg = (crcReg << 1);
		crcData <<= 1;
	}
	return crcReg;
} // culSmallCRC8




//----------------------------------------------------------------------------
//  byte culSmallCRC8Block(...)
//
//	Description:
//	    A CRC-8 (DOW) implementation optimized for small code size on blocks
//      of data. For the invocation on the first and/or only block the value
//      CRC8_INIT should be given for _crcReg_. The value returned
//		is the CRC-8 of the data supplied so far. This CRC-value should be
//		added at the end of the data to facilitate a later CRC check. During
//		checking the check should be performed on all the data AND the CRC-8
//		value appended to it. The data is intact if the value returned is 0.
//
//	Arguments:
//		byte* crcData
//			A pointer to the block of data to perform the CRC-8 operation on.
//      word length
//          The number of bytes in this block.
//		byte crcReg
//			The current value of the CRC register. For the first block the
//			value CRC8_INIT should be supplied. For each additional block the
//			value returned for the last invocation should be supplied.
//
//	Return value:
//		The updated value of the CRC8 register. This corresponds to the 
//		CRC-8 of the data supplied so far. During CRC checking, after working
//		through all the data and the appended CRC-8 value, the value will be
//		0 if the data is intact.
//----------------------------------------------------------------------------
byte culSmallCRC8Block(byte* crcData, word length, byte crcReg) {
    word j;
	byte i, dataByte;

    for (j = 0; j < length; j++) {
        dataByte = *crcData++;
    	for (i = 0; i < 8; i++) {
    		if ((crcReg & 0x80) ^ (dataByte & 0x80))
    			crcReg = (crcReg << 1) ^ CRC8_POLY;
    		else
    			crcReg = (crcReg << 1);
    		dataByte <<= 1;
    	}
    }
    return crcReg;
} // culSmallCRC8Block