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Altera_Forum's avatar
Altera_Forum
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13 years ago

Weak pull-up setting is ignored

Hi, please help me with this issue. I am stuck with enabling weak pull-up on the I/O pins. I set whole bus's defined by the location earlier weak pull-ups to ON, but fitter ignores it. How to do it properly? I read about constraints, but they should not apply here!

4 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    Don't know what you did exactly. Programmablé (weak) pull-up can be enabled in the Pin Planner or Assignment Editor.

  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    I'm not sure what you mean by "the fitter ignores it" but the pullup may be weaker than you think. Try using the Assignment Editor to assign "Passive Resistor" which can be pulled either up or down.

  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    Passive resistor option: quartus help says "This option is used in functional simulations only".

    Is there any way to _physically_ pull up the signal other than weak pull-up (which seems to be insufficient) and external resistor (which is another device on the board)?
  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    Be sure to have your pins as INOUT or IN. Setting "weak pull-up" in the assignment editor has always worked for me.