Resolution 1 This issue occurs only with the behavioral model of the FIFO Generator v5.2 core. To work around this error, generate a structural model for the core.
To do so:
1. Double-click on the "Manage Cores" process in the ISE software when highlighting the core, or create a new CORE Generator standalone project.
2. In the CORE Generator project properties, select "Structural" for the Simulation Model selection.
The simulation should now run successfully.
This is a known issue in ISim 11.3 and newer updates. The issue has been fixed in ISE Design Suite 12.1.
To download and install the latest version of ISE Design Suite, visit the Download Center at
http://www.xilinx.com/support/download/index.htmResolution 2 This fatal error can occur when there is no signal at the right side of any of the statements inside an always block. This results in always@* returning "NULL", causing a fatal error.
An example of such an always block is as follows:
always @(*) begin
xaui_clk_ready <= 1'b1;
end
This is a known issue with ISim in previous updates of ISE Design Suite 11. The issue has been fixed in ISE Design Suite 11 Update 4 (11.4) . Please download and install the latest ISE software update from the Download Center at:
http://www.xilinx.com/support/download/index.htm