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PANHA's avatar
PANHA
Icon for New Contributor rankNew Contributor
9 months ago

Inquiry About DFFE Input/Output Connection in Quartus

I would like to ask a quick question regarding the DFFE connection in Quartus.

As I observed in the symbol, there is a bubble (inverter) before both the PRN and CTRN inputs.

In this case, if I connect a High signal to PRN or CTRN, will the internal PRN and CTRN signals stay High, or will they become Low due to the inverter?

If there are any official documents, application notes, or recommended practices you could share on this topic, I would be grateful.

Thank you very much for your support.

Programmable Logic Device

3 Replies

  • FvM's avatar
    FvM
    Icon for Super Contributor rankSuper Contributor
    8 months ago
    "As I observed in the symbol, there is a bubble (inverter) before both the PRN and CTRN inputs.

    In this case, if I connect a High signal to PRN or CTRN, will the internal PRN and CTRN signals stay High, or will they become Low due to the inverter?"
    No. The circle doesn't indicate an inverter before "internal PRN". It indicates active low function of PRN, also letter N does the same. But it's not an inverter before an active low input.

    Connecting high respectively VCC to an active low input deactivates the input, leaving the pin open does the same.
  • ShengN_altera's avatar
    ShengN_altera
    Icon for Super Contributor rankSuper Contributor
    9 months ago

    Hi,


    They will become low due to inverter because they're active low.


    Thanks,

    Regards,

    Sheng


  • ShengN_altera's avatar
    ShengN_altera
    Icon for Super Contributor rankSuper Contributor
    8 months ago

    Hi,


    May I know do you have any further concern or consideration?


    Thanks,

    Regards,

    Sheng