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AR# 41144

ISE Simulator (ISIM) - Memory Leak can occur on Linux when infinite loop occurs

Description

Certain coding constructs which can lead to an infinite loop occurring in simulation can also cause memory leaks in ISE Simulator.

In older versions, for example 11.x, this issue would crash a machine due to the memory leak and the machine would need to be rebooted.

In later software releases, ISE Simulator produces an error stating that the application needs to close.

"The simulator has terminated in an unexpected manner. Please review the ISim log (isim.log) for details."

An example of code which can cause this problem can be seen here:

--- begin code

process

begin

if(clk'event and clk = '1') then

gen_input <= gen_input_next;

end if;

cnt <= cnt + 1;

end process;

--- end code

Solution

Improvements made in the tool to reduce the number of memory leaks in ISE Simulator.

Errors will now occur to close down the GUI instead of allowing ISIM to run until the memory leak occurs.

For the above example you will see a Warning message similar to the following when running the simulation:

WARNING:HDLCompiler:1369 - "####.vhd" Line ##: Possible infinite loop; process does not have a wait statement

To fix this issue, add a sensitivity list and add the "cnt <= cnt + 1" line into the if statement as follows:

--- begin code

process(clk)

begin

if(clk'event and clk = '1') then

gen_input <= gen_input_next;

cnt <= cnt + 1;

end if;

end process;

--- end code


AR# 41144
Date Created 03/09/2011
Last Updated 10/01/2014
Status Active
Type General Article
Tools
  • ISE Design Suite - 11.2
  • ISE Design Suite - 11.3
  • ISE Design Suite - 12.1
  • More
  • ISE Design Suite - 12.2
  • ISE Design Suite - 12.3
  • ISE Design Suite - 12.4
  • ISE Design Suite - 13.1
  • Less