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AR# 59634

LogiCORE IP DisplayPort v4.0 - Why do I see a AUX channel timeout when performing larger AUX channel transactions?


Why do I see an AUX channel timeout when performing larger AUX channel transactions?


In the DisplayPort v4.2 and earlier, the timeout circuit was starting its count too early.  

If large transactions were delayed too long, this would cause the core to time out.  

The timeout counter has been fixed in the DisplayPort v4.2 (Rev. 1) core in Vivado 2014.1 or later.

Users should still make sure that they are not violating the 400us timeout in the DisplayPort Specification as it can cause failures in AUX communications.  

This can happen if the DisplayPort Sink delays the start of a large transaction until close to the limit of 300us.  

If the transaction does not complete before 400us, then the DisplayPort Sink core will time out.

For example an AUX channel read of 12-16 bytes that starts close to the end of the 300us DisplayPort Sink reply limit of 300us, might take long enough to cause a timeout to occur in the DisplayPort Source.

If users find that they cannot meet the 400us timeout then they can work around this by breaking up larger transactions into smaller transactions that will complete before the 400us timeout.

Linked Answer Records

Master Answer Records

Answer Number Answer Title Version Found Version Resolved
54522 LogiCORE IP DisplayPort - Release Notes and Known Issues for Vivado 2013.1 and newer tool versions N/A N/A
AR# 59634
Date Created 03/04/2014
Last Updated 05/28/2014
Status Active
Type General Article
  • DisplayPort