topic What should be the value of seed and generator polynomial? in S32K

What should be the value of seed and generator polynomial?

beingalpha18 — Wed, 22 Jul 2020 10:48:23 GMT

Hi,

I am using CRC module of S32K142, But I am not able to understand what should be the value of seed and generator polynomial for real CRC calculation on data.

Re: What should be the value of seed and generator polynomial?

kef2 — Wed, 22 Jul 2020 18:35:05 GMT

Hi,

Seed and poly depends on CRC type. This routine works for 16 bits CRC-CCITT (0x1021 poly):

unsigned int crc16(const void* buf, size_t len)

{

char oddlen;

union{

unsigned char *c;

unsigned short *s;

unsigned long *l;

}ptr;

PCC->PCCn[PCC_CRC_INDEX] |=PCC_PCCn_CGC_MASK;

CRC->CTRL |= CRC_CTRL_TCRC_MASK;

CRC->GPOLY = 0x10210000; // poly <<16

CRC->CTRL |= CRC_CTRL_WAS_MASK;

CRC->DATAu.DATA = 0x0;

CRC->CTRL &= ~CRC_CTRL_WAS_MASK;

ptr.l = (void*)buf;

oddlen = len & 3;

len /= 4u;

while(len--)

{

CRC->DATAu.DATA = __builtin_bswap32(*ptr.l++);;

}

while(oddlen--)

{

CRC->DATAu.DATA_8.LL = *ptr.c++;

}

return CRC->DATAu.DATA_16.H;

}

Edward

Re: What should be the value of seed and generator polynomial?

Robin_Shen — Tue, 28 Jul 2020 06:21:06 GMT

Hi Mr Alpha,

You can read: Understanding and implementing CRC (Cyclic Redundancy Check) calculation

seed also calls initial value

Hope it helps!

Best Regards,

Robin

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