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Altera_Forum's avatar
Altera_Forum
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17 years ago

Adding On-Chip Terminations in Quartus

Hi all ... hopefully a simple question (ha ha ha ... don't they all start that way)

We've got a design that we're looking to clean up some signal integrity issues on and want to add the on-chip termination resistors. (Background details: Cyclone III, 16K chip, using Quartus 7.2 SP1)

We've gone into the Assignment Editor and for the pins in question we've added the following entries:

- In "I/O Features" we've added the pins in the "To" field

- Set "Assignment Name" to "Output Termination"

- Set "Value" to "Series 50 Ohm with Calibration" and

- Set "Enabled" to Yes

Now, my hardware guru goes on those pins with a scope and finds the rise and fall time to be identical ... which he feels indicates that the termination resistors weren't added.

Is there something else / something different we need to do to add these resistors?

Thanks

7 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    To see whether Quartus used your settings, check the "Output Termination" column in the "Output Pins" or "Bidir Pins" table in the "Resource Section" part of the Fitter compilation report. If the pin table does not list the terminations, perhaps there is a warning message about the settings not taking effect. Not all problem settings produce warnings though.

  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    Go into the Compilation Report -> Fitter -> Resource Section -> Output Pins and see if those pins have the termination on. Another place to look would be from this report, right-click on a particular port and Locate to Chip Editor. This will show it highlighed in the Chip Editor. Double clock on the port and the Resource Property Editor will come up, showing a graphical representation of what's going on inside the IO cell. If it's not there, the next step would be to figure out why the assignment didn't take(look through messages for something on this assignment...)

  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    Thanks all ... appreciate the quick replies. Turns out that was the default, so the reason we didn't see any change was that there wasn't any when we explicitly added in the terminations.

  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    You could have choosen minimum drive strength before which isn't very different from 50 ohms series termination.

  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    As FvM said, you can try changing the drive strength. Dropping the drive strength should help. Sometimes the default drive strength is a bit too much.

    Also review the signal's routing.