AR# 16287

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Schematic - "ERROR:NgdBuild:466 - output pad net '' has illegal connection" is reported for a schematic design with bidirectional ports

Description

My design passes schematic design rule checks, but NGDBuild errors similar to the following are reported during the translate process:

"Checking expanded design ...

ERROR:NgdBuild:466 - output pad net 'd0' has illegal connection

ERROR:NgdBuild:466 - output pad net 'd1' has illegal connection

ERROR:NgdBuild:466 - output pad net 'd2' has illegal connection

ERROR:NgdBuild:466 - output pad net 'd3' has illegal connection"

Solution

These errors occur if the ECS schematic design uses bidirectional ports and I/O buffer symbols are present on the output, but not on the input.

For example:

If a bidirectional port is connected to the output of an OBUFT and to the D input of an FD register symbol, the errors above are reported.

To correct the problem, add an appropriate input I/O buffer symbol. The example above will be fixed if an IBUF symbol is placed between the port and the D input of the FD (or by using an IFD symbol in place of the FD symbol).

AR# 16287
Date 12/15/2012
Status Active
Type General Article
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