CRC problems on MC33771

[andyworsley]

Hi, I am trying to implement code for the MC33771, but I'm struggling to make sense of the CRC description in the datasheet. It uses a 9 bit polynomial 0x12F, but on page 41 it shows, what I presume is, a hardware implementation where X8 is the same as X0, so X8 doesn't operate on the current CRC value, but on the incoming data from the stream. However, the diagram below it shows all 9 bits operating on the CRC.

I've been trying for several days to get this to work, using every combination I can think of, with no success. I have also tried a number of online checkers, all of which come up with different answers to the ones in the examples in the datasheet.

As this project has incredibly tight timescales, I'm really up against it, so if anyone has sample code that works with this polynomial or an algorithm that does, I would be very grateful.

Thanks

Andy

[prabusekar]

Hi Sir, i am writing code communicate with MC33771 through MC33664 ,using TPL Communication( sample code )

SPI0 as master (tx) - NXP S32K144

SPI2 as slave(rx)- NXP S32K144 -Microcontroller

i send write data via spi0 (TX),i am getting echo data  only in spi2( rx) 

NO RESPONSE FROM MC3371

it happen both write and read command 

pls help me

Regards 

Prabu.S

[TomasVaverka]

Hello Prabu,

I can provide you an example code as well as an application note with basic guidelines for the configuration and programming of the MC33771 BCC.

However, it cannot be shared without a signed NDA with your NXP Sales Representative or Distributor. Then please create a private support ticket.

Thank you for your understanding.

Best regards,

Tomas

[prabusekar]

Thank you Sir, 

Now i can Communicate With MC33771.

[regregex]

Hello Andy,

What is the document number/URL of the manual you referred to? I can only find short factsheets (MC33664FS, MC33772FS, MC33772SM).  I'm particularly interested as the CRC algorithm appears to be unique.

Thanks

Greg

[TomasVaverka]

Hello Greg,

Full datasheets are available under NDA. You will need to contact our local sales office or distributor to sign the required NDA to get the datasheets.

Best regards,

Tomas

[TomasVaverka]

Hi Andy,

Attached you can find the CRC calculation software implemented on our Kinetis KL25Z MCU.

Hope it helps.

Regards,

Tomas

PS: If my answer helps to solve your question, please mark it as "Correct" or “Helpful”. Thank you.

[andyworsley]

Thanks Tomas,

that code works! I did notice that the code uses a seed of 0x42, where the datasheet says it should be 0xFF. Is this an error in the datasheet?

Regards

Andy