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AR# 35034

Design Assistant for PCI Express - Completion Timeouts Cause the System to Freeze


This article discusses that completion timeouts may result in system hangs.

Note: This Answer Record is a part of the Xilinx Solution Center for PCI Express(Xilinx Answer 34536) TheXilinx Solution Center for PCI Express is available to address all questions related to PCIe. Whether you are starting a new design with PCIe or troubleshooting a problem, use the Solution Center for PCIeto guide you to the right information.


The most common cause of a system hang or freeze is due to a completion timeout occurring on the host. In other words, the root complex issued a read to the endpoint and the endpoint does not return a completion.

The user needs to ensure the application is draining incoming packets and returning completions for any Non-Posted packets. In most cases these will be memory reads.

If a completion timeout is expected, use ChipScope analyzer on the user application interface to ensure completions are being returned for received memory reads.

Revision History
08/13/2010 - Initial Release

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AR# 35034
Date 12/15/2012
Status Active
Type General Article
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