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AR# 39446

Virtex-6 - GTX TXPLLLKDET RXPLLLKDET / Spartan-6 - PLLLKDET - Lock Signals Do Not Return to LOW when REFCLK Stops

Description

In Virtex-6, why is the GTX PLL lock indicator set HIGH, even if the REFCLK is a flat line?

Solution

After achieving a lock status, the Virtex-6 GTX TXPLLLKDET and RXPLLLKDET signals do not return to LOW if the REFCLK suddenly stops. 

The same situation happens with PLLLKDET in Spartan-6 GTP.

For those designs where the REFCLK is not free running, or has holes, the presence of the REFCLK must be monitored in the fabric.

AR# 39446
Date Created 08/02/2011
Last Updated 10/02/2014
Status Active
Type Known Issues
Devices
  • Virtex-6 CXT
  • Virtex-6 LX
  • Virtex-6 LXT
  • More
  • Virtex-6 SXT
  • Spartan-6 LXT
  • Less