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AR# 4240

4.1i XC4000 MAP - Connection to TDO pad lost when signal is merged (WARNING::x4kdr:23...The comp..."DIA_RSCI" does not have any pins that are being used")

Description

Keywords: merge, trim, unconnected, IOB, EPIC

Urgency: Hot

General Description:
MAP loses the connection to a TDO pad when the net driving the TDO pad is merged into another net. The circuit has the following configuration:

DFF->INV->INV->OBUF->TDO

The resulting circuit included a configured TDO component with no net attached; this leads to the following DRC warning:

WARNING:x4kdr:23 - Blockcheck: The comp (mapped physical logic cell) "DIA_RSCI" does not have any pins that are being used.

Solution

This problem can be avoided by putting a KEEP (no merge) property on the net driving the OBUF:

NET netname KEEP;
AR# 4240
Date Created 07/13/1998
Last Updated 08/20/2003
Status Archive
Type General Article