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AR# 63704

UltraScale GTH/GTY - How to switch to use internal PRBS pattern generator when using Async Gearbox mode


When the async gearbox is enabled, the PRBS generator cannot be enabled by switching the TXPRBSSEL port.   



Assuming a GT is configured to operate in Async Gearbox mode, the following steps must be taken to get the PRBS generator to function.

To return to Async Gearbox mode, undo all of the changes and reset the PCS. 

Some of the changes are to attributes, so DRP is required. 

  1. Put the PCS into reset by asserting TXPCSRESET.
  2. Set the attribute TXGEARBOX_EN = 1'b0 via DRP.
    Originally it is 1'b1.
  3. Set the port TXOUTCLKSEL to 3'b010 (TXOUTCLKPMA).
    Originally it is 3'b101 (TXPROGDIVCLK).
  4. Set the attribute TXBUF_EN = 1'b1 (Enable TX Buffer) via DRP.
    Originally it is 1'b0
  5. Set TXPRBSEL and RXPRBSEL to the desired PRBS pattern.
    Originally it is 4'b0000 (Pat Gen/Chk off)
  6. Release TXPCSRESET
This procedure will be documented in future versions of both the UltraScale GTH and GTY User Guides. 
AR# 63704
Date Created 02/25/2015
Last Updated 04/08/2015
Status Active
Type General Article
  • Kintex UltraScale
  • Virtex UltraScale