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TMS320F28335: Can XINTF accommodate for read strobe high to Output High impeadance time?

stevenh
Guru 20035 points

Hello

The flash device I am using has a timing parameter named tDF (=Output enable high to Output High-Z time = 16ns). The Output enable is essentially the Read strobe.

XINTF doesn't seem to allow for this time in the Trail time.

Does the XINTF have any way to deal with the tDF time period?

Thanks,
Stephen

  

  • 0
    Genius 3735 points

    Stephen,

    The trail time should cover your scenario.  It can be set up to 6 clock cycles long; assuming the max clock of 150 MHz that would be 40 nsec, more than sufficient to cover 16 nsec.

    Regards,

    Bill

  • 0 in reply to Bill Finger
    Guru 20035 points

    Hello Bill,

    Thanks for the reply.

    Doesn't the trail time only take care of the time between the read/write stobe going high and the chip select (i.e. output enable) going high.  I had thought that once the chip select goes high, the trail time period will complete ( see page 14 of SPRU949D).  Am I incorrect?

    Stephen  

  • 0 in reply to stevenh
    Genius 3735 points

    It is the time from after the strobe goes high until the chip select goes high.  The timing parameter for your memory was from when nOE (same as nXRD) goes high until output-high-Z.  Setting the trailing parameter correctly will prevent other devices from trying to use the data lines until the device has gone to high impedance.  See timing diagram below.

    Regards,

    Bill

  • 0 in reply to Bill Finger
    Guru 20035 points

    Hello Bill,

    Ok, I thought about it again.  You are correct.  

    The output going high-z is dependent only on nOE going high and not Chip select.

    The flash timing diagram shows nOE and chip select going high at the same time.  It also has the tDF parameter measured with respect to both of them.  I had thought the output going to high-z had to occur after the chip select going high, which is not correct.

    Thanks, 

    Stephen