topic Re: CRC: bytewise vs. wordwise different results in Kinetis Microcontrollers

CRC: bytewise vs. wordwise different results

xarowubas — Mon, 14 May 2018 13:46:46 GMT

Device: K60 (little-endian)

I program in assembly.

If I write 4 bytes representing the ASCII string "abcd" as a 32 bit *word* to CRC_CRC, I get a different checksum than when I write 4 single bytes in the order 'a', 'b', 'c', 'd' to CRC_CRC[LL], i.e., 4 separate STRB instructions.

Why?

results for wordwise calculation:

input: abcd
checksum: 0x79A5961D

input: dcba
checksum: 0x1D39469F

results for bytewise calculation:

input: abcd
checksum: 0x1D39469F

input: dcba
checksum: 0x79A5961D

Re: CRC: bytewise vs. wordwise different results

Robin_Shen — Wed, 16 May 2018 09:01:22 GMT

Hi Xaro,

Don't know how you configure the CRC module.
Have you try to refer the crc example in SDK_2.2_TWR-K60D100M(C:\SDK_2.2_TWR-K60D100M\boards\twrk60d100m\driver_examples\crc)?

I can only get the result 0xED82CD11 by using online CRC calculation.

I can also get the same result from K60 running crc example in SDK_2.2_TWR-K60D100M.

Best Regards,

Robin

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Re: CRC: bytewise vs. wordwise different results

Robin_Shen — Thu, 14 Jun 2018 09:13:30 GMT

wordwise calculation

If you debug that example, you can see the value write into CRC_DATA is 0x64636261

bytewise calculation:

base->ACCESS8BIT.DATALL = *data;

input a(0x61)

input b(0x62)

input c(0x63)

input d(0x64)

Best Regards,

Robin