UPGRADE YOUR BROWSER

We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

AR# 14546

6.1i XST - "WARNING:Xst:646 - Signal <signal_name> is assigned but never used." Is the alias construct supported?

Description

Keywords: XST, VHDL, alias, construct, support

Urgency: Standard

General Description:
When I use the alias construct, a number of the following errors are reported:

"WARNING:Xst:646 - Signal <signal_name> is assigned but never used."
"XST 524: All outputs of the instance <instance_name> of the block <module_name> are unconnected in block <block_name>."

Solution

The alias construct is not fully supported in XST; the following alias constructs are not supported:

- An alias of an alias
- An alias declaration without subtype_indication
- Signatures on alias declarations
- An operator symbol as alias_designator
- An alias of an operator symbol
- Character literals as alias designators
- An alias to user-defined functions

Some issues with the alias construct are fixed in the latest 5.2i Service Pack available at:
http://support.xilinx.com/xlnx/xil_sw_updates_home.jsp
The first service pack containing the fix is 5.2i Service Pack 2.
AR# 14546
Date Created 04/23/2002
Last Updated 10/20/2005
Status Archive
Type General Article