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AR# 44505

13.3 XST - "ERROR:HDLCompiler:1831 - "<*>.v" Line <*>: Complex expression in event control"

Description

XST produces following messages when it comes across a complex expression in event control:

"ERROR:HDLCompiler:1831 - "<*>.v" Line <*>: Complex expression in event control
INFO - You can change the severity of this error message to warning using switch -change_error_to_warning "HDLCompiler:1831"

Solution

This error occurs if the sensitivity list of an event control statement contains a complex expression that is not a plain signal or the posedge/negedge of a signal.

Take the following piece of code as an example:

module top (
input clk,
input en,
input b,
output reg q );

always@(posedge clk & en) // event expression is too complex
begin
end
endmodule

The Verific XST (version 13.3) will give the following error message for the above piece of code:
"ERROR:HDLCompiler:1831 - "top.v" Line 3: Complex expression in event control
INFO - You can change the severity of this error message to warning using switch -change_error_to_warning "HDLCompiler:1831""

AR# 44505
Date Created 10/13/2011
Last Updated 05/19/2012
Status Active
Type Error Message