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Altera_Forum
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12 years ago

Cyclone IV - Using high impedance in GPIO

I have a project with 14 bidir. I use to test integrated circuits from college.

i use the 36 gpio pins in a protoboard with a flat cable. but when i put the bidir in high impedance, all outputs go to high level (but they continue in high impedance).

Firstly i think the weak pull-up resistor is on (and turn off). After I tried turn off all programmable adjustments. Nothing worked.

I am a computer scientist and maybe my fail is in eletronic level. I don't know.

Any suggestions? What can you do to help me?

6 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    What is driving the wire when you put the FPGA pins in high impedance?

  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    Since there isn't anything else driving the wire, when the bidir signals go into high-impedance state, the status present in the wire is "random".

  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    --- Quote Start ---

    Since there isn't anything else driving the wire, when the bidir signals go into high-impedance state, the status present in the wire is "random".

    --- Quote End ---

    So, why can I do?
  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    --- Quote Start ---

    So, why can I do?

    --- Quote End ---

    What's the problem?

    If you need them low add very high value pull down resistors from each line to gnd.

    ?

    Nial