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# 10668

3.1i WebPACK XST - "ERROR: NGDBuild:467 - output pad net '' has an illegal buffer"


Keywords: WebPACK, OBUFT, OBUF, tri, 3-state, web, pack, NGDBuild, NGD, build, buffer

Urgency: Standard

General Description:
When using an OBUFT in a schematic design in WebPACK for an XC9500 device, I encounter the following "NGDBuild:467" error:

ERROR: NGDBuild:467 - output pad net '' has an illegal buffer.


This has been fixed in WebPACK 4.1i.

Work-around for WebPACK 3.1i:

The bug prevents XST from realizing that the OBUFT is an output buffer; therefore, XST places an OBUF after the OBUFT. This is an illegal connection, which generates the error in NGDBuild.

The work-around is to use the OBUFE with an inverter on the enable line; this provides logic that is equivalent to an OBUFT. XST properly recognizes the OBUFE as an output buffer.
AR# 10668
Date Created 04/08/2014
Last Updated 08/20/2014
Status Archive
Type General Article