#define POLYNOMIAL 0x8005 //#define USE_CRC_TABLE #ifndef USE_CRC_TABLE static unsigned short crc_table[256]; #else static unsigned short crc_table[256] = {0x0000, 0x8005, 0x800F, 0x000A, 0x801B, 0x001E, 0x0014, 0x8011, 0x8033, 0x0036, 0x003C, 0x8039, 0x0028, 0x802D, 0x8027, 0x0022, 0x8063, 0x0066, 0x006C, 0x8069, 0x0078, 0x807D, 0x8077, 0x0072, 0x0050, 0x8055, 0x805F, 0x005A, 0x804B, 0x004E, 0x0044, 0x8041, 0x80C3, 0x00C6, 0x00CC, 0x80C9, 0x00D8, 0x80DD, 0x80D7, 0x00D2, 0x00F0, 0x80F5, 0x80FF, 0x00FA, 0x80EB, 0x00EE, 0x00E4, 0x80E1, 0x00A0, 0x80A5, 0x80AF, 0x00AA, 0x80BB, 0x00BE, 0x00B4, 0x80B1, 0x8093, 0x0096, 0x009C, 0x8099, 0x0088, 0x808D, 0x8087, 0x0082, 0x8183, 0x0186, 0x018C, 0x8189, 0x0198, 0x819D, 0x8197, 0x0192, 0x01B0, 0x81B5, 0x81BF, 0x01BA, 0x81AB, 0x01AE, 0x01A4, 0x81A1, 0x01E0, 0x81E5, 0x81EF, 0x01EA, 0x81FB, 0x01FE, 0x01F4, 0x81F1, 0x81D3, 0x01D6, 0x01DC, 0x81D9, 0x01C8, 0x81CD, 0x81C7, 0x01C2, 0x0140, 0x8145, 0x814F, 0x014A, 0x815B, 0x015E, 0x0154, 0x8151, 0x8173, 0x0176, 0x017C, 0x8179, 0x0168, 0x816D, 0x8167, 0x0162, 0x8123, 0x0126, 0x012C, 0x8129, 0x0138, 0x813D, 0x8137, 0x0132, 0x0110, 0x8115, 0x811F, 0x011A, 0x810B, 0x010E, 0x0104, 0x8101, 0x8303, 0x0306, 0x030C, 0x8309, 0x0318, 0x831D, 0x8317, 0x0312, 0x0330, 0x8335, 0x833F, 0x033A, 0x832B, 0x032E, 0x0324, 0x8321, 0x0360, 0x8365, 0x836F, 0x036A, 0x837B, 0x037E, 0x0374, 0x8371, 0x8353, 0x0356, 0x035C, 0x8359, 0x0348, 0x834D, 0x8347, 0x0342, 0x03C0, 0x83C5, 0x83CF, 0x03CA, 0x83DB, 0x03DE, 0x03D4, 0x83D1, 0x83F3, 0x03F6, 0x03FC, 0x83F9, 0x03E8, 0x83ED, 0x83E7, 0x03E2, 0x83A3, 0x03A6, 0x03AC, 0x83A9, 0x03B8, 0x83BD, 0x83B7, 0x03B2, 0x0390, 0x8395, 0x839F, 0x039A, 0x838B, 0x038E, 0x0384, 0x8381, 0x0280, 0x8285, 0x828F, 0x028A, 0x829B, 0x029E, 0x0294, 0x8291, 0x82B3, 0x02B6, 0x02BC, 0x82B9, 0x02A8, 0x82AD, 0x82A7, 0x02A2, 0x82E3, 0x02E6, 0x02EC, 0x82E9, 0x02F8, 0x82FD, 0x82F7, 0x02F2, 0x02D0, 0x82D5, 0x82DF, 0x02DA, 0x82CB, 0x02CE, 0x02C4, 0x82C1, 0x8243, 0x0246, 0x024C, 0x8249, 0x0258, 0x825D, 0x8257, 0x0252, 0x0270, 0x8275, 0x827F, 0x027A, 0x826B, 0x026E, 0x0264, 0x8261, 0x0220, 0x8225, 0x822F, 0x022A, 0x823B, 0x023E, 0x0234, 0x8231, 0x8213, 0x0216, 0x021C, 0x8219, 0x0208, 0x820D, 0x8207, 0x0202 }; #endif void gen_crc_table(); unsigned short update_crc(unsigned short crc_accum, unsigned char *data_blk_ptr, unsigned short data_blk_size); void gen_crc_table() { #ifndef USE_CRC_TABLE register unsigned short i, j; register unsigned short crc_accum; /* 0 ~ 255 까지의 CRC를 미리 계산 */ /* ex) i=2 이면 0x020000 을 polynomial로 CRC 나눗셈 하는 것임 */ for(i=0; i<256; i++) { crc_accum = ((unsigned short)i<<8); /* CRC나눗셈이 가능하도록 8-bit shift */ for(j=0; j<8; j++) { /* 나머지항의 MSB가 1인지 검사 */ if(crc_accum & 0x8000L) crc_accum = (crc_accum << 1) ^ POLYNOMIAL; /* 참이면 1-bit shift하고 polynomial을 빼줌(==XOR) */ else crc_accum = (crc_accum << 1); /* 거짓이면 1-bit shift만 함*/ } /* 결과적으로 총 16-bit가 shift 되었고 */ /* 나머지만 남게 됨 */ crc_table[i] = crc_accum; //printf("%03d=%04x, ", i, crc_accum); //if(i%7 == 0) // printf("\n"); } #endif return; } /* 이전에 계산한 CRC 값을 추가된 데이터에 맞춰 갱신함 이전: ___________ 8005 | XX 00 00 yy yy ---> CRC 갱신: ______________ 8005 | XX ZZ 00 00 yy yy 00 ww ww ---> CRC' */ unsigned short update_crc(unsigned short crc_accum, unsigned char *data_blk_ptr,unsigned short data_blk_size) { register unsigned short i, j; for(j=0; j> 8) ^ *data_blk_ptr++) & 0xff; crc_accum = (crc_accum << 8) ^ crc_table[i]; /* 나머지항의 하위 바이트는 뒤에 0x00 이 */ /* 추가되어 자리수가 올라가고 앞자리의 */ /* 나머지와 더해짐 */ } return crc_accum; } /********************************************************** CRC-16 test sample **********************************************************/ void main() { unsigned short crc, check; unsigned char in_frame[20]; unsigned char out_frame[20]; gen_crc_table(); /* 임의 데이터 생성 */ in_frame[0] = 0x55; in_frame[1] = 0xA1; in_frame[2] = 0x12; in_frame[3] = 0x34; /* 송신측의 CRC 생성 */ crc = update_crc(0, in_frame, 4); printf("\n====== CRC-16 Demo ========\n"); printf("\nTransmitter CRC result = %X", crc); /* 수신측의 검증 */ out_frame[0] = in_frame[0]; out_frame[1] = in_frame[1]; out_frame[2] = in_frame[2]; out_frame[3] = in_frame[3]; out_frame[4] = (crc & 0xFF00) >> 8; out_frame[5] = (crc & 0x00FF); check = update_crc(0, out_frame, 6); printf("\nReceiver CRC check = %X\n", check); }