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8位crc校验分析及程序

科普小知识2022-03-20 08:32:11
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CRC 中的生成多项式,是有很多标准的。其统一的规律是:最高位、最低位都为1。8位CRC校验通常用的是CRC-8,其生成多项式为:107H = 1 0000 0111B进行异或运算时,最高位,就算是移出去了,因此,只用 07H 进行异或计算即可。

CRC校验实用程序库 在数据存储和数据通讯领域,为了保证数据的正确,就不得不采用检错的手段。在诸多检错手段中,CRC是最著名的一种。CRC的全称是循环冗余校验,其特点是:检错能力极强,开销小,易于用编码器及检测电路实现。从其检错能力来看,它所不能发现的错误的几率仅为0.0047%以下。

从性能上和开销上考虑,均远远优于奇偶校验及算术和校验等方式。因而,在数据存储和数据通讯领域,CRC无处不在:著名的通讯协议X.25的FCS(帧检错序列)采用的是CRC-CCITT,WinRAR、NERO、ARJ、LHA等压缩工具软件采用的是CRC32,磁盘驱动器的读写采用了CRC16,通用的图像存储格式GIF、TIFF等也都用CRC作为检错手段。下面介绍硬件生成与计算CRC的过程。

8位CRC校验程序

//本程序是完成CRC-8的方程式为X^8+X^2+X+1的源代码,经调试后正确通过!

#include “reg52.h”

#define CRCnum 5

char CRCArray[CRCnum]={0x16,0x0f,0x17,0xe9,0x03};//需要CRC计算一串数0x160f17e903

unsigned char cal_crc(unsigned char *ptr, unsigned char len);

void main()

{

char CRC;

CRC=cal_crc(CRCArray,CRCnum);//得到CRC的代码

}

unsigned char cal_crc(unsigned char *ptr, unsigned char len)

{

unsigned char i; unsigned char crc=0; while(len--!=0)

{

for(i=0x80; i!=0; i/=2)

{

if((crc&0x80)!=0)

{

crc*=2; crc^=0x07;

} /* 余式CRC乘以2再求CRC */

else

crc*=2;

if((*ptr&i)!=0)

crc^=0x07; /* 再加上本位的CRC */ } ptr++;

}

return(crc);

}

CRC8位校验程序分析

crc8校验查表法实现方法——查表法 生成多项式X^8+X^6+X^4+X^3+X^2+X^1

const uchar crctable[] = {

0, 94,188,226, 97, 63,221,131,194,156,126, 32,163,253, 31, 65,

157,195, 33,127,252,162, 64, 30, 95, 1,227,189, 62, 96,130,220,

35,125,159,193, 66, 28,254,160,225,191, 93, 3,128,222, 60, 98,

190,224, 2, 92,223,129, 99, 61,124, 34,192,158, 29, 67,161,255,

70, 24,250,164, 39,121,155,197,132,218, 56,102,229,187, 89, 7,

219,133,103, 57,186,228, 6, 88, 25, 71,165,251,120, 38,196,154,

101, 59,217,135, 4, 90,184,230,167,249, 27, 69,198,152,122, 36,

248,166, 68, 26,153,199, 37,123, 58,100,134,216, 91, 5,231,185,

140,210, 48,110,237,179, 81, 15, 78, 16,242,172, 47,113,147,205,

17, 79,173,243,112, 46,204,146,211,141,111, 49,178,236, 14, 80,

175,241, 19, 77,206,144,114, 44,109, 51,209,143, 12, 82,176,238,

50,108,142,208, 83, 13,239,177,240,174, 76, 18,145,207, 45,115,

202,148,118, 40,171,245, 23, 73, 8, 86,180,234,105, 55,213,139,

87, 9,235,181, 54,104,138,212,149,203, 41,119,244,170, 72, 22,

233,183, 85, 11,136,214, 52,106, 43,117,151,201, 74, 20,246,168,

116, 42,200,150, 21, 75,169,247,182,232, 10, 84,215,137,107, 53};

备注:在数据传输中CRC或传过来的数据,可能低字节在前,高字节在后,这就造成查表法表中被查数据不同。

unsigned char crc_array[256] = {

0x00, 0x5e, 0xbc, 0xe2, 0x61, 0x3f, 0xdd, 0x83,

0xc2, 0x9c, 0x7e, 0x20, 0xa3, 0xfd, 0x1f, 0x41,

0x9d, 0xc3, 0x21, 0x7f, 0xfc, 0xa2, 0x40, 0x1e,

0x5f, 0x01, 0xe3, 0xbd, 0x3e, 0x60, 0x82, 0xdc,

0x23, 0x7d, 0x9f, 0xc1, 0x42, 0x1c, 0xfe, 0xa0,

0xe1, 0xbf, 0x5d, 0x03, 0x80, 0xde, 0x3c, 0x62,

0xbe, 0xe0, 0x02, 0x5c, 0xdf, 0x81, 0x63, 0x3d,

0x7c, 0x22, 0xc0, 0x9e, 0x1d, 0x43, 0xa1, 0xff,

0x46, 0x18, 0xfa, 0xa4, 0x27, 0x79, 0x9b, 0xc5,

0x84, 0xda, 0x38, 0x66, 0xe5, 0xbb, 0x59, 0x07,

0xdb, 0x85, 0x67, 0x39, 0xba, 0xe4, 0x06, 0x58,

0x19, 0x47, 0xa5, 0xfb, 0x78, 0x26, 0xc4, 0x9a,

0x65, 0x3b, 0xd9, 0x87, 0x04, 0x5a, 0xb8, 0xe6,

0xa7, 0xf9, 0x1b, 0x45, 0xc6, 0x98, 0x7a, 0x24,

0xf8, 0xa6, 0x44, 0x1a, 0x99, 0xc7, 0x25, 0x7b,

0x3a, 0x64, 0x86, 0xd8, 0x5b, 0x05, 0xe7, 0xb9,

0x8c, 0xd2, 0x30, 0x6e, 0xed, 0xb3, 0x51, 0x0f,

0x4e, 0x10, 0xf2, 0xac, 0x2f, 0x71, 0x93, 0xcd,

0x11, 0x4f, 0xad, 0xf3, 0x70, 0x2e, 0xcc, 0x92,

0xd3, 0x8d, 0x6f, 0x31, 0xb2, 0xec, 0x0e, 0x50,

0xaf, 0xf1, 0x13, 0x4d, 0xce, 0x90, 0x72, 0x2c,

0x6d, 0x33, 0xd1, 0x8f, 0x0c, 0x52, 0xb0, 0xee,

0x32, 0x6c, 0x8e, 0xd0, 0x53, 0x0d, 0xef, 0xb1,

0xf0, 0xae, 0x4c, 0x12, 0x91, 0xcf, 0x2d, 0x73,

0xca, 0x94, 0x76, 0x28, 0xab, 0xf5, 0x17, 0x49,

0x08, 0x56, 0xb4, 0xea, 0x69, 0x37, 0xd5, 0x8b,

0x57, 0x09, 0xeb, 0xb5, 0x36, 0x68, 0x8a, 0xd4,

0x95, 0xcb, 0x29, 0x77, 0xf4, 0xaa, 0x48, 0x16,

0xe9, 0xb7, 0x55, 0x0b, 0x88, 0xd6, 0x34, 0x6a,

0x2b, 0x75, 0x97, 0xc9, 0x4a, 0x14, 0xf6, 0xa8,

0x74, 0x2a, 0xc8, 0x96, 0x15, 0x4b, 0xa9, 0xf7,

0xb6, 0xe8, 0x0a, 0x54, 0xd7, 0x89, 0x6b, 0x35,

};