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AR# 3895

Foundation, Translate: Where does the &__A__ net name in my warning come from?

Description

Keywords: Foundation, Translate, ngdbuild, basnu, &__A__

Urgency: Standard

General Description:

When running through the Xilinx Implementation tools with
Foundation, Ngdbuild (translate) produces warnings/errors
regarding nets named similar to:

&__A__17 <-- The number may be different.

The problem is that these nets do not make sense to the user
because he/she did not name any nets in the design like this.
How can one debug this problem?

Solution

The Foundation edif netlist generator labels unnamed busses
using this form (&__A__#).
Depending on the Warnings/Errors, the problem lies with the
busses defined by the hierarchy of the message. If you only
have one bus at that specified hierarchy, then work with that
bus to resolve the issue.

To avoid the default naming, be sure to label each bus.

For troubleshooting, if after labelling each bus, you continue
to have default bus labels (&__A__#) in warnings/errors, you
can export your design as an xnf netlist. Do this in the
Foundation schematic editor:
1. In the schematic editor, from the top level sheet, select
Options - Export Netlist.
2. Then select the file type as Xilinx and select the top level
.alr or .alb file.
3. Click on Open.

This will generate .xnf netlists for the design.

4. Move the top-level edif from the working directory (it can
be deleted).
5. Run the implementation tools by starting the Design Manager.
Do not start the Design Manager through the Foundation
Project Manager, instead, goto Start - Programs - Xilinx...
- Design Manager.
6. Create a new project. Point to the top-level xnf file as the design file and give a different name for the working directory (eg ...\xproj -> ...\xproj2).
7. Run through the implementation.

The Warning/Error messages should now point to specific bus names, rather than the default &__A__# labels. Use these
specific names to debug the design.

Some things to look for:
1. Make sure that when connecting a bus to a macro, that the
bus has the correct number of bits for the macro pin.
2. Make sure that if you tap off bits of a bus, and you use the
remaining bits in a macro, that the new segment of bus,
after the tapping, has a label with the correct bit width.
3. Make sure that if a bus is connected to a macro pin, that
the full bus width is used within the macro, rather than
just part of the whole bus that is connected to the pin. It
is best to reduce the macro pin bus width rather than drop
the unused bits within the macro.

AR# 3895
Date Created 05/11/1998
Last Updated 08/12/2003
Status Archive
Type General Article