CS4210 Datasheet, PDF (32/102 Pages) National Semiconductor (TI) – IEEE 1394 OHCI Controller

Operational Description (Continued)
ff ff ff ff ff ff ff ff -> CRC1 = feh, CRC2 = 70h
01 23 45 67 89 ab cd ef -> CRC1 = 19h, CRC2 = 07h
00 00 00 00 00 00 00 00 -> CRC1 = bfh, CRC2 = f4h
#include <stdio.h>
typedef unsigned char uchar_t;
typedef unsigned short ushort_t;
typedef unsigned long long_t;
ushort_t calc_crc(ushort_t r, uchar_t d);
ushort_t rev16(ushort_t src);
/* main routine */
int main(int argc, char *argv[])
{
ushort_t residual = 0xffff;
int din;
uchar_t byte;
uchar_t crc1, crc2;
while(scanf("%2x", &din ) != EOF ) {
byte = din;
printf("%2.2x ", byte);
residual = calc_crc(residual, byte);
};
printf("\n");
residual = rev16(residual);
crc1 = ~(residual & 0x00ff);
crc2 = ~(residual>>8);
printf("CRC1 = %2.2hxh\n", crc1);
printf("CRC2 = %2.2hxh\n", crc2);
return(0);
/* calc_crc - apply a byte of data to the 16-bit CRC */
}
ushort_t calc_crc(ushort_t r, uchar_t d)
{
ushort_t bit_in;
int i;
for(i=0;i<8;i++) {
bit_in = (d>>i) & 0x0001;
if((r>>15) ^ bit_in)
r = (((r<<1) & 0x7ffb) | ((r>>15 ^ ((r>>14)&0x0001) ^ bit_in) << 15) |
((r>>15 ^ ((r>>1)&0x0001) ^ bit_in) << 2) | 0x0001 );
else
r <<= 1;
}
return(r);
}
ushort_t rev16(ushort_t src)
{
return(
((src&0x0001)<<15) |
((src&0x0002)<<13) |
((src&0x0004)<<11) |
((src&0x0008)<<9) |
((src&0x0010)<<7) |
((src&0x0020)<<5) |
((src&0x0040)<<3) |
((src&0x0080)<<1) |
((src&0x0100)>>1) |
((src&0x0200)>>3) |
((src&0x0400)>>5) |
((src&0x0800)>>7) |
((src&0x1000)>>9) |
((src&0x2000)>>11) |
((src&0x4000)>>13) |
((src&0x8000)>>15);
}
Figure 3-1. CRC1 and CRC2 Sample Code
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