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AR# 38550

Virtex-6 GTX and Spartan-6 GTP Transceivers - How do I enable "lock-to-reference" mode?


Previous Xilinx Serial Transceivers allowed for a "lock-to-reference" mode, which would force the CDR to lock to the reference clock and not track the incoming data. Do the Virtex-6 GTX or Spartan-6 GTP Transceivers have this functionality?


You can set both the Virtex-6 GTX and Spartan-6 GTP Transceivers so that the CDR is locked to the reference clock rather than the incoming data, which is the case when oversampling the incoming data. As such, the values for PMA_RX_CFG that correspond to oversampling can be used for lock-to-reference mode:

Virtex-6 GTX: PMA_RX_CFG =25h05CE000
Spartan-6 GTP:PMA_RX_CFG = 25h0F44000

NOTE: These settings disable the CDR, and, as a result, RXRECCLK is not synchronous to incoming data.

Linked Answer Records

Associated Answer Records

Answer Number Answer Title Version Found Version Resolved
37907 Virtex-6 GTX / Spartan-6 GTP - How to lock to REFCLK N/A N/A
AR# 38550
Date Created 01/10/2011
Last Updated 02/21/2013
Status Active
Type General Article
  • Virtex-6 CXT
  • Virtex-6 HXT
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