qdn_crc.c

/*
 **************************************************************************
 *
 *     ROM CRC CALCULATION CODE
 *
 **************************************************************************
 *
 *  This file contains the CRC generating routines and the CRC table.
 *
 *  The 16 bit CRC routines use the same standard CCITT16 16 bit
 *  generating polynomial (x16 + x12 + x5 + 1) used by the XMODEM
 *  communication protocol.
 * representations:
 * normal:0x1021, reversed: 0x8408, reciprocal: 0x8810
 *
 * This is also the same as the CRC16 0x11021 calculation that is performed
 * by IAR/EWARM ielftool.
 *
 *  Every possible arrangement of 1, 2, or 3 bit errors will be detected. 
 *  Nevertheless, there remains a small possibility that some errors will 
 *  not be detected--this happens when the pattern of the errors results 
 *  in a new value which, when divided, produces exactly the same remainder 
 *  as the correct block.  With a properly constructed 16-bit CRC, there is 
 *  an average of one error pattern which will not be detected for every 
 *  65,535 which would be detected.  That is, with CRC-CCITT, we should 
 *  be able to detect 65535/65536ths or 99.998 percent of all possible errors.
 *
 **************************************************************************
 */



/*
 *  SYSTEM INCLUDE FILES
 *************************
 */




/*
 *  USER INCLUDE FILES
 ***********************
 */


#include "g8_crc.h"
#define WORD uint16_t
#define BYTE uint8_t


/*
 *  USER DEFINES / MACROS
 **************************
 */

#define CRC_INIT      (0x0000)  /*  Initial value for CRC calculation */



/*
 *  DATA DECLARATIONS (EXTERNS, GLOBALS, STATICS)
 **************************************************
 */



/*  CRC lookup table */

const WORD crc_table[256] = {

	0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7, 
	0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF, 
	0x1231, 0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6, 
	0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE, 
	0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485, 
	0xA56A, 0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D, 
	0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4, 
	0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC, 
	0x48C4, 0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823, 
	0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B, 
	0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12, 
	0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A, 
	0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41, 
	0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49, 
	0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70, 
	0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78, 
	0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F, 
	0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067, 
	0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E, 
	0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256, 
	0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D, 
	0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405, 
	0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C, 
	0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634, 
	0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB, 
	0x5844, 0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3, 
	0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A, 
	0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92, 
	0xFD2E, 0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9, 
	0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1, 
	0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8, 
	0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0 
	
};




/*
 *********************************************************************
 *
 *     crc_buffer_calc()
 *
 *     Called to calculate the CRC of a buffer.
 *
 * ENTRY:
 *    buf - byte pointer to array over which to calculate the CRC
 *    len - number of bytes in the buffer
 *
 * EXIT:
 *    WORD - 16-bit CRC of buffer contents
 *
 *********************************************************************
 */


WORD G8_CRC_BufferCalc(const BYTE *buf, uint32_t len)  {
    WORD crc;
    uint32_t k;
    BYTE const *cptr;

    /*  Loop through data buffer and generate CRC  */
    crc = CRC_INIT;

    for (k = 0, cptr = buf; (k < len); k++, cptr++) {
        update_crc((*cptr), crc, crc_table);
    }

    return(crc);
}