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AR# 33422

ISE Simulator (ISim) - Error "tracing limit is reached. Signal tracing will stop!"


Keywords: Tracing Limit

I am able to launch a simulation of my design using ISim. However, after it has run for some time, I encounter the following error:

"tracing limit is reached. Signal tracing will stop!"

What is a "tracing limit" and how can I resolve this issue?



A "tracing limit" is a limit on the total number of transitions that can be stored in the Waveform Database (wdb) file for viewing in the Waveform Viewer based on the available system memory. This error can occur when the simulator is unable to allocate enough memory to store a large number of transitions occurring in a simulation.

To resolve this issue, you can do one of two things:

- Install the latest ISE Design Suite 11 Update. Running the latest version of the simulator offers enhanced memory usage, allowing for simulations to run longer with a larger number of waveform transitions.

- Add to the Wave window only the signals that are relevant to the verification process. For example, not all top level signals are of interest in a given simulation session. Removing traced signals from the Wave window results in less memory consumption, allowing the simulator to simulate to completion without issuing the error.


The tracing limit error can occur prematurely on machines with large amount of memory available. This is a known issue with ISim in ISE Design Suite 11 tools and it has been fixed in ISE Design Suite 11 Update 4 (11.4) .

Please download and install the latest ISE Design Suite update from the Download Center at: http://www.xilinx.com/support/download/index.htm.
AR# 33422
Date Created 09/08/2009
Last Updated 11/19/2009
Status Active
Type General Article