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Delfino 28335 XINTF use

Mike52327
Intellectual 450 points


Hello All,

In our HW design, we are using a delfino 28335 micro with NVRam (FRAM) from cypress.  Per the NVrams data sheet, if using chip select control (as the DSPs xintf does), we need to grantee a 55ns period where the chip select line remains high.  However, the Xintf does not allow for such.

The other possible way to interface with the NVRam is to keep the chip select low all the time.

So my question, is it valid to use the xintf of this DSP, but override the chipselect line and configure it as a GPIO and pull it low all the time?  The xintf will still be setup and will control the address lines, data lines, read and write lines as well.

Thanks

-mike

  • 0
    TI__Guru 61235 points
    Mike,

    The XINTF doesn't care about the chip select signal. It provides it only for the external device, and also so that you can interface more than one device to the XINTF using different CSn zones. If you want to tie the CSn line active all the time on the NVRam (or whatever you need to do for the particular chip), you can do so.

    If you have more than one device on the XINTF however, be careful. They'd better not both be chip selected at the same time, at least not for read operations!

    Regards,
    David
  • 0 in reply to David M. Alter
    Intellectual 450 points

    Thanks for the info.  Since we only have one device off the xintf, that works for out needs... 

    One more follow up question, do accesses to the xintf block interrupts?  We have a NVRam module off the xintf and have both an interrupt and main loop accessing the memory.  Variables are declared volatile as needed, but can an interrupt happen in the middle?  As an example, during the Active timing of an xintf read?  I could not see any mention of this in the xintf user guide.

    Thanks,

    -mike

  • 0 in reply to Mike52327
    TI__Guru** 115971 points

    Hi Mike,

    Interrupt will be only serviced after active read access is complete.

    Regards,


    Vivek Singh