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AR# 20391

XST - "ERROR:Xst:1468 - "file.v" line xx: Unexpected event in always block sensitivity list"

Description

The following error occurs when I try to use the Verilog 2001 combinational sensitivity list (always @*) when reading a two-dimensional array:

"ERROR:Xst:1468 - "file.v" line xx: Unexpected event in always block sensitivity list"

Example

reg [1:0] lock_valid[1:0];

reg a ;

always @*

begin

if (lock_valid[0] == 2'b00)

a = 1'b1 ;

else

a = 1'b0 ;

end

Solution

You must have all the elements of the array in the two-dimensional array that is read in the sensitivity list.

To work around this issue, use the following:

reg [1:0] lock_valid[1:0];

reg a ;

always @(lock_valid[0],lock_valid[1])

begin

if (lock_valid[0] == 2'b00)

a = 1'b1 ;

else

a = 1'b0 ;

end

This issue is fixed for Virtex-6 and Spartan-6 devices.

AR# 20391
Date Created 09/03/2007
Last Updated 12/15/2012
Status Active
Type General Article