To enable metastability mean time between failures (MTBF) analysis and optimization in the Quartus® II software version 9.0, you must identify which registers are part of a synchronization register chain.
Setting the Auto value for the global Sychronizer Identification setting on the TimeQuest Timing Analyzer page of the Settings dialog box generates a list of likely synchronization chains in your design, based on the software’s automatic synchronizer detection criteria. However, MTBF is not reported or optimized for automatically detected synchronizer register chains.
Altera recommends applying the Synchronizer Identification option Forced If Asynchronous to each register in a synchronization chain. Instance-specific assignments ensure that the software analyzes an accurate set of synchronizers to report an accurate MTBF. If you use the global Auto Synchronizer Identification setting to detect likely synchronizers, you must still use specific assignments to identify the true synchronizers for MTBF analysis. Apply the Synchronizer Identification option using the Assignment Editor or Tcl assignments.
For complete details about metastability MTBF reporting in the Quartus II software, refer to the Managing Metastability with the Quartus II Software (PDF) chapter in volume 1 of the Quartus II Handbook.