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AR# 58606

14.7 Route - WARNING:Route:438 - The router has detected an unroutable situation due to local congestion

Description

The following error occurs during PAR in ISE Design Suite.

How can I resolve it?


WARNING:Route:438 - The router has detected an unroutable situation due to local congestion. The router will finish the 
rest of the design and leave one or more connections as unrouted. The cause of this behavior might be putting too 
much logic into a single CLB. To allow you to use FPGA editor to isolate the problems, the following is a list of (up 
to 10) such congested connections: 

Congestion on : OMUX(32168,-13919) signal : xxx 
Congestion on : OMUX(32168,-13919) signal : xxx
Congestion on : OMUX(30309,-16616) signal : xxx
......

Solution

In general this error occurs because the CLB resource is over utilized which result in OMUX routing congestion.

An OMUX in this context refers to the output switchbox paths available to the components in the CLB tile.

To resolve this error, first check in FPGA Editor to see where these signals come from.
 
  1. If these signals come from the BRAM and Multiplier, please refer to (Xilinx Answer 32080).
     
  2. If these signals come from normal slice logics inferred from the code, check if LOC or RLOC constraints are used on these logics.
    Evaluate if the resources within the CLB are over-utilized under these constraints and change the constraints accordingly.
     
  3. If these signals come from a user defined Macro, evaluate if the resources within the CLB are over-utilized in the Macro and modify the Macro accordingly.
     
  4. Sometimes using different cost table helps to resolve the error.




AR# 58606
Date Created 12/02/2013
Last Updated 03/23/2015
Status Active
Type General Article
Tools
  • ISE Design Suite