Forum Discussion

anonimcs's avatar
anonimcs
Icon for Contributor rankContributor
1 year ago
Solved

Enable on-chip termination for Differential Transceiver clocks

Hi all, I was wondering what .qsf assignments I would need to enable on-chip termination for my differential transceiver clocks. The target device is an Arria10. When I tried using the line below, I...
Configuration
Generic Io
  • FvM's avatar
    FvM
    1 year ago

    Hi,

    as far as I understand you are still searching for valid .qsf entry for transceiver clock input termination.

    Valid settings are listed in this document: https://www.intel.com/content/www/us/en/docs/programmable/683296/24-3.html
    As far as I see, the settings are the same for previous Quartus Pro versions.

    The option for transceiver reference clock termination is XCVR_A10_REFCLK_TERM_TRISTATE

    allowed values are TRISTATE_OFF and TRISTATE_ON

    TRISTATE_OFF corresponds to 100 ohm differential termination.

    Some confusion is caused by the fact, that Quartus Std. uses a different option name
    XCVR_REFCLK_PIN_TERMINATION

    values are AC_COUPLING, DC_COUPLING_EXTERNAL_RESISTOR and DC_COUPLING_INTERNAL_100_OHMS

    See: https://www.intel.com/content/www/us/en/docs/programmable/683084/current/settings-file-reference-manual.html

    To check which termination has been actually implemented, you can review QPP fitter report/Plan Stage/Input Pins.


    Regards
    Frank

AR_A_Intel's avatar
AR_A_Intel
Icon for Super Contributor rankSuper Contributor
1 year ago

Hi

For enabling on-chip termination in your Arria 10 transceiver clocks, the correct syntax varies based on whether you’re working with differential inputs or need specific resistance values. Intel typically recommends the following .qsf assignments for Arria 10:

set_instance_assignment -name INPUT_TERMINATION "DIFFERENTIAL 100 OHM" -to clk_xcvr_1 -entity myDesign

This is the preferred method for specifying 100-ohm differential termination on transceiver reference clocks. Make sure your entity name and clock name (clk_xcvr_1 in this example) match your design.

For more information refer: https://www.intel.com/content/www/us/en/docs/programmable/683084/current/xcvr-a10-rx-term-sel.html


  • anonimcs's avatar
    anonimcs
    Icon for Contributor rankContributor
    1 year ago

    Hi,

    I can try that for sure, but I don't get that my design works with an invalid syntax for the clock termination. It's a differential clock and 100 ohm internal termination is recommended, so I would expect the things to go wrong when I used the syntax I posted. Could you tell me why ?

    Kind regards