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AR# 14681

4.1i XST - "WARNING:Xst:646 - Signal <signal_name> is assigned but never used"

Description

Keywords: XST, 4.1i, natural, optimized, not used, unconstrained, vector

Urgency: Standard

General Description:
When I use a signal declaration of the type "natural", with an unconstrained length similar to the following:

signal signal_name : natural;

the following message is returned in the synthesis report when XST optimizes the signal out:

"WARNING:Xst:646 - Signal <signal_name> is assigned but never used."

Solution

To fix this problem, constrain the natural variable.

In this example, the corrected line would be:

signal signal_name : natural range 0 to 3;
AR# 14681
Date Created 05/15/2002
Last Updated 08/06/2003
Status Archive
Type General Article