Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

Warning: Found 20 output pins without output pin load capacitance assignment?

What is the method to find this info? Rough estimates usually adequate?

Where do these numbers go into Quartus?

2 Replies

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

    Unless you have a very timing-critical design, I believe this is one of the MANY Quartus II compilation warning messages that you can ignore. At least until you get down to the final optimization of the design.

    Anyone else have comments on this?
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    14 years ago

    I got the same warning, because the default cap load is 0pF for the pin output type you have specified. If you go to the Assignments/Device... tab and click on the "Device and Pin Options..." button, you will find "Capacitive Loading" under Category:. Here you can set the default load cap for the output driver type in your design.

    I find this useful for output timing analysis. It will also help you choose the minimum output drive strength to meet your desired output timing.