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SN74AVC4T774: NOR Flash does not boot the FPGA when rebooting. (Read)

KIM Andy
Expert 2530 points
Part Number: SN74AVC4T774
Other Parts Discussed in Thread: TS3A5018

HI

My customers are using the SN74AVC4T774 and have encountered the following problems.

* Circuit configuration

- SN74AVC4T774 was used for NOR Flash SPI communication.
- Communicates over the Selection (OE * pin) in the DSP / FPGA.
- The OE * pin is pulled down to communicate with the Default FPGA during initial operation.
 
* problem
   NOR flash download is possible after initial boot (wirte)
   However, NOR Flash does not boot the FPGA when rebooting. (Read)
 
* Debugging situation
1. After removal of U5 level shifter, confirm that download and booting are normal after SPI Direct connection.
2. Remove the U6 parts and use the U5 alone.
 
Because it is a part dedicated to SPI communication, we applied it at this stage.
Since the part is removed and normal operation is performed, please check whether there is a debugging point in the part separately.

  • 0
    TI__Mastermind 46045 points

    Hi Andy,

    Can you explain the issue in terms of our device, I'm not really sure what the issue is. Also, it doesn't look like they are level shifting since both supplies are at 1.8 V. What exactly are they trying to achieve?

    Also additional info like scope captures of the issue would be very beneficial.

  • 0 in reply to Dylan Hubbard
    Expert 2530 points
    Hi 
    thank you for your quick reply.
    As you said, the IC is not a role of level shifting.
    Customers use the SN74AVC4T774 for switching purpose.
    The problem is that if the IC is removed and the SPI is connected directly, it will work normally.
    However, if you mount it for use as above, you will not boot the FPGA when rebooting. (Read)
  • 0
    Guru 317370 points

    What direction are the FPGA data signals (DO0, DO1)? Their names imply they have both the same direction, but the two channels are configured differently.

    Anyway, it would have been simpler to use a four-channel analog switch like the TS3A5018.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 46045 points

    Hi Kim,

    I don't see any configuration issues with our device so I don't see why it would be working. I second Clemens' question, to see if the signal directions are accurate. Those aren't bidirectional signal lines are they? The pin names seem to indicate a dual SPI interface.

  • 0 in reply to Dylan Hubbard
    TI__Mastermind 46045 points

    Hi Kim,

    I haven't heard from you in a few days so I assume the problem has been resolved and will mark this thread as so. If not feel free to post a response to reopen the thread and I can continue to support.