51单片机的CRC程序通过查表的办法进行计算对于51单片机相当适用

51单片机的CRC程序，此程序是通过查表的办法进行计算，对于51单片机相当适用

1. 
   
2. 
   
3. #define BYTE_BITS 8 // Number of bits in byte<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
   
4. #define TABLE_SIZE  1<<BYTE_BITS // Size of table
   
5. #define WIDTH 16 // width of poly(number of most significnt bit)
   
6. #define MSB_MASK    1<<(WIDTH-1) // Mask for high order bit in word
   
7. #define POLY 0x1021 // Ploy. Bit #16 is set and hidde
   
8. typedef unsigned short Crc16;
   
9. Crc16 table[TABLE_SIZE];
   
10. void crc16init()
    
11. {
    
12. Crc16 i, val,t1,t2;
    
13. int j;
    
14. for(i=0;i<TABLE_SIZE;++i)
    
15. {
    
16. val=i<<(WIDTH-BYTE_BITS);
    
17. for(j=0;j<BYTE_BITS;++j)
    
18. {
    
19. t1= val<<1;
    
20. t2=((val&MSB_MASK) ? POLY : 0);
    
21. val=t1^t2;
    
22. }
    
23. table[i]=val;
    
24. }
    
25. }
    
26. 
    
27. Crc16 crc16(Crc16 crc, void const* src, int cnt)
    
28. {
    
29. unsigned char const* s=(unsigned char const*)src;
    
30. while(cnt--)
    
31. crc=(crc<<BYTE_BITS)^table[(crc>>(WIDTH - BYTE_BITS)) ^ *s++];
    
32. return crc;
    
33. }
    
34. 
    
35. void main()
    
36. {
    
37. unsigned char data[12]={0x54, 0xD3, 0x07, 0x0C, 0x17, 0x45, 0x0B,0x0E ,0x19,0,0};
    
38. Crc16 result;
    
39. crc16init();
    
40. result=crc16(0,&data[0],9);
    
41. data[9]=(result>>8)&0xff;
    
42. data[10]=result&0xff;
    
43. result=crc16(0,&data[0],11);
    
44. 
    
45. }<!--EndFragment-->
    

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