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Altera_Forum's avatar
Altera_Forum
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13 years ago

state of unprogrammed or powered off fpga pins

Hi everyone,

I would like to know the state of pins of an unprogrammed (blank or no config device) or powered off cyclone 4 FPGA, specifically whether it is safe to pull them up/down while in this state. I would also like to know if it is safe to do this while the device is being programmed i.e the bitstream is in the process of being shifted in. (the program will set these pins to inputs).

details: I have a cyclone IV board which I am going to connect to the GPIOS of an ARM SOC, I would like to be able to run the SOC (generally holding the connections to the FPGA high) without necessarily severing the connection or previously configuring the FPGA.

Thanks for the answers,

S

1 Reply

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    13 years ago

    Driving within rated voltage range is possible, the pins are high-Z respectively expose a weak pull-up. Refer to "Hot socketing" and "Power-on-reset-circuitry" sections in device manual for details.