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AR# 13801

7.1i XST - "ERROR:Xst:853 - Unsupported item in port list for module <module_name>"


Keywords: Verilog, HDL, port, list, XST

Urgency: Standard

General Description:
XST reports the error below when I attempt to describe an "anonymous port" in Verilog 2001, or when a Verilog sub-module has a port list with port widths as follows:

module my_ff(clk,ff_in[7:0],rst,ff_out[7:0],en);
input clk;

"ERROR:Xst:853 - Unsupported item in port list for module <module_name>"



Anonymous Port

NOTE: You can use an anonymous port to describe ports that have no internal connection. This is useful when your design is implemented with a pre-determined interface (set of ports), but the design does not need to connect to one or more ports internally.

Example of an anonymous port:

module ff (d, clk, q, );

The empty space after the port "q" is the anonymous port. XST does not currently support anonymous ports.


Port Width Declared in the Port Listing
Declaring port widths in the port listing is standard Verilog coding; however, declaring ports widths in the port listing is not currently supported in Verilog sub-modules. To work around this issue, declare the widths of the ports in the port declarations and not in the port lists.
AR# 13801
Date Created 08/29/2007
Last Updated 10/23/2008
Status Archive
Type General Article