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LP87745-Q1: SPI CRC calaculation

Frank QIN
Expert 6465 points
Part Number: LP87745-Q1
Other Parts Discussed in Thread: AWR2944, LP87745

Hi Team,

We are using the LP87745 powering a AWR2944. We would like to turn on the SPI CRC.

According to the datasheet 8.5.1.1, the polynomial is 0x107, with Big-Endian. We are not sure the default value is 0xFF or 0x01, the output result is reversed.

During the test, the CRC value read was recorded. The value read back from 5E is 0x00, the CRC is 0x74. When value is 0x10, CRC is 0x04.

We tried different configuration, like different default value, different permutation. But we can't calculate the correct value same as the CRC value.

So we want to get an example. Like, when register 5E is 0x00, how should we calculate the CRC? What is the value we need to input and what is the default value and result?

Thanks!

Best,

Frank

  • 0
    TI__Guru* 78773 points

    Hi Frank,

    The device expert is out on Monday (holiday in Finland) and should be able to answer your question on Tuesday. 

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    TI__Expert 8990 points

    Hi Frank,

    The normal representation of polynomial is 0x07, Big-endian, initial value is 0xFF and no output result inversion .  The result inversion point will be updated in datasheet in new revision. 

    For SPI CRC calculation of 5E with 0x00, you need to include following data.

    0x5e, 0x10, 0x00 and then you will get 0x74 because SPI calculation includes, register adress + (page+0+reserved) + DATA bits. 

     

    BR,

    Ishtiaque