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SPC560P40 eDMA feeds CRC engine. Wrong CRC values produced

jamesteske9
Associate II

‎2015-04-08 08:10 AM

Posted on April 08, 2015 at 17:10

I am hoping someone has experience using the CRC engines with success.  I am feeding the CRC input register with 32 or 16 or 8 bit sizes of the same data and the CRC produces different outputs.  I have to be doing something wrong.  Seeded with $FFFFFFFF.  Any special concerns with using the eDMA or the CRC would be appreciated.

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3 REPLIES 3
jamesteske9
Associate II

‎2015-04-09 12:48 PM

Posted on April 09, 2015 at 21:48

I found out from the helpful folks at ST that the CRC generator does not put out a CRC16-CCITT or a CRC32 ethernet as advertized without a little bit of manipulation first.  Since it is pretty tough to get a DMA to do this manipulation, it is nearly impossible to send data into the CRC engine with a DMA and expect the industry standard CRC results.  Check erratas for info about using the CRC engine that missed getting into the RM0022.

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Erwan YVIN
ST Employee

‎2015-04-28 06:19 AM

Posted on April 28, 2015 at 15:19

Hello James ,

Sorry for the late answer.

 I am checking in our side if we have an application note to help you.

      Best Regards

                   Erwan

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Erwan YVIN
ST Employee

‎2015-05-27 09:08 AM

Posted on May 27, 2015 at 18:08

Hello James ,

Did you solve your issue ? When i populate the CRC Engine by byte / by word. i have the same result. we have tested by SW or by HW (8 bits /32 bits) .. the result is the same . 

(crc_struct[instance].CRC_n)->CNTX[instance].CRC_INP.W = WORD;
or
(crc_struct[instance].CRC_n)->CNTX[instance].CRC_INP.B[0] = ((uint8_t)(WORD & 0x000000FF));
(crc_struct[instance].CRC_n)->CNTX[instance].CRC_INP.B[1] = ((uint8_t)((WORD & 0x0000FF00) >> 8));
(crc_struct[instance].CRC_n)->CNTX[instance].CRC_INP.B[2] = ((uint8_t)((WORD & 0x00FF0000) >> 16));
(crc_struct[instance].CRC_n)->CNTX[instance].CRC_INP.B[3] = ((uint8_t)((WORD & 0xFF000000) >> 24));

/*-----------------------------------------------------------------------*/ Parameters: polynom : 0x4C11DB7 order : 32 crcinit : 0xFFFFFFFF direct, 0x46AF6449 nondirect crcxor : 0xFFFFFFFF refin : 1 refout : 1 Results: /*-----------------------------------------------------------------------*/ Expected value is = 0xE951A406 Actual value from IPs is = 0xE951A406 Test passed Tomorrow, i am going to send to you a non-official application developped from ''SPC5Studio''. Have you got a small example of your application ? Best regards Erwan
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