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TMS320F2808: Any hardware arbitration for eQep QPOSCNT ?

Simen Biao
Expert 1875 points
Part Number: TMS320F2808


Hi,

Any hardware arbitration for QPOSCNT when we write a value into the QPOSCNT and QCLK also occur to cause QPOSCNT Increment /Decrement?
What  happens with QPOSCNT ?

Using F2808 eQep, sometimes we can not write a value into QPOSCNT when  QCLK cause QPOSCNT Increment /Decrement.

Is this normal?


best regards.
Simen

  • 0
    TI__Genius 15385 points

    Hi Simen,

    In general purpose usage QPOSCNT should be Read ONLY register, while it is incrementing/decrementing on QCLK event.

    Let me get back to you with the specific details on the circuit behavior under these conditions.

    Regards,

    Nirav

  • 0 in reply to Nirav Ginwala
    TI__Genius 15385 points

    Hi Simen,

    More details to the earlier message - Once position counter QPOSCNT is enabled, it will act as Read ONLY register and any writes to it will have no effect. You can write into it for initialization before enabling, but not after it is enabled.

    Can you please provide a brief description on the requirements to write into the QPOSCNT while it is Incrementing/Decrementing?

    Regards,

    Nirav

  • 0 in reply to Nirav Ginwala
    Expert 1875 points

    Hi Nirav,

    Thanks for your answers.

    But,

    1. Could you point out "Once position counter QPOSCNT is enabled, it will act as Read ONLY register and any writes to it will have no effect" on user guide ?

    2. We can always write into QPOSCNT register, just sometimes have no effect. So suspect that QPOSCNT is written into conflict.

    best regards,

    Simen

  • 0 in reply to Simen Biao
    TI__Genius 15385 points

    Hi Simen,

    It is not mentioned in the user guide yet, but we can add to it. 

    In your application, when do you write into to the QPOSCNT register? Like I mentioned once it is enabled the writes will not have any effect.

    Regards,

    Nirav 

  • 0 in reply to Nirav Ginwala
    Expert 1875 points

    Dear Nirav,

    1. Customer has modified their algorithm to avoid it happen. They will close this issue.

    2. It is better if TI can add it to all c28x user guide " Once position counter QPOSCNT is enabled, it will act as Read ONLY register and any writes to it will have no effect. "

    Thank you.

    best regards,

    Simen

  • 0 in reply to Simen Biao
    TI__Genius 15385 points

    Hi Simen,

    Definitely, we will add it to the Technical Reference Manual.

    Thanks & Regards,

    Nirav