Internal Error: Sub-system: CDB, File: /quartus/db/cdb/cdb_net_sys.cpp, Line: 3973

Description

Due to a problem in the Quartus® II software version 12.0 SP1 and earlier, you may see this error if your design contains a tristate output pin if the Fitter packs the output enable register into an IO element and the data input of the tristate buffer is tied to a constant logic '1'.

Resolution

To avoid this problem, perform one of the following actions:

• Use the Fast Output Enable Register assignment set to Off to prevent the Fitter from packing the output enable register into the IO element
• Connect data input of the tristate buffer to a non-static signal

This problem is fixed beginning with the Quartus II software version 12.1.