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