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Altera_Forum's avatar
Altera_Forum
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16 years ago

Cyclone III power up

When I power up the cyclone III board I see a 2.5V ~100msec pulse on the HSMC Bidirectional ports. From what I understand it is due to a weak pullup resitor on the output. I found in the pin planner you can add a column "weak pullup resistor" on/off then I turned the outputs I was using "off" but it had no effect. Anyone have an idea where I can turn this option off or if I can? If I check the Assignment editor under I/O Features it shows them off as well.

From what I read (Hot socketing and Power on Reset document) I have no choice but to use a stronger pull down R to prevent it from triggering my cct during power up.

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

    --- Quote Start ---

    From what I read (Hot socketing and Power on Reset document) I have no choice but to use a stronger pull down R to prevent it from triggering my cct during power up.

    --- Quote End ---

    Quite right. To prevent false output signals during power up, you can either use a high idle state of the respective IOs or external pull-down resistors.