Article ID: 000083970 Content Type: Troubleshooting Last Reviewed: 07/25/2013

Why are VCC_CLKIN power supplies for transceiver REFCLK required to be connected to 1.5V source as reported in Quartus II Fitter Report?

Environment

  • Cyclone® IV GX FPGA
  • Quartus® II Subscription Edition
  • BUILT IN - ARTICLE INTRO SECOND COMPONENT
    Description

    All VCC_CLKIN supplies require 2.5V sources when used to power the transceiver REFCLK input pins. The REFCLK pins are powered by these dedicated VCC_CLKIN3A, VCC_CLKIN3B, VCC_CLKIN8A, and VCC_CLKIN8B power supplies separately in their respective I/O banks.

     

    When REFCLK pins are assigned to the supported I/O standarads such as 1.5 PCML I/O standard in Quartus® II software version beginning with 11.0, the Fitter reports invalid VCC_CLKIN level. This is a software bug.

     

    Please make sure that the VCC_CLKIN supplies are tied to 2.5V source on your board.

     

    This issue is not observed if you are using a Quartus II software version eariler than 11.0.

    Resolution

    This issue is resolved in the Quartus II software version 12.1.

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