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AR# 45148

7 Series GTX GTH CTLE and DFE frozen setup

Description

In 7 series GTX and GTH, how can I stop the Linear Equalizer and the DFE from continuously adapting and freezing the current setup?

Solution

If freezing the linear equalizer and the DFE is necessary, the following ports should be driven to 1'b1:

GTX and GTH:
RXDFEAGCHOLD
RXDFELFHOLD
RXDFETAP2HOLD
RXDFETAP3HOLD
RXDFETAP4HOLD
RXDFETAP5HOLD
RXDFEUTHOLD
RXDFEVPHOLD
RXDFEOSHOLD
RXLPMHFHOLD
RXLPMLFHOLD

GTH only
RXDFETAP6HOLD
RXDFETAP7HOLD
RXDFESLIDETAPHOLD

Cases when keeping the DFE in hold mode is recommended:

For scrambled data or for scrambled and encoded data, the adaptation algorithm provides the best equalization result in any temperature, voltage and silicon variation.

In case of non random patterns (i.e., in the very particular case when a comma is sent forever in a 8B10B encoded signal), the adaptation algorithm could bring to a wrong state and should be suspended.

The "hold" condition should follow a training period where the pattern is not random. It is difficult to know in advance when the received pattern will be random, but it is possible to check the received data and eventually repeat the DFE adaptation in case received data is a long series of the same comma which may cause an adaptation failure.

AR# 45148
Date Created 08/31/2012
Last Updated 01/10/2014
Status Active
Type General Article
Devices
  • Kintex-7
  • Virtex-7
  • Artix-7