Device Family: Intel® Stratix® 10

Intel Software: Quartus Prime Pro

Type: Answers

Area: Tools


Last Modified: May 17, 2019
Version Found: v19.1
Bug ID: 1409335092

Why does the synchronizer chain "altera_std_synchronizer_nocut" have unsafe MTBF in the metastability report in Timing Analyzer?

Description

Due to a problem with the Intel® Quartus® Prime Pro edition version 19.1, the synchronizer chain "altera_std_synchronizer_nocut" might  have an unsafe Mean Time between Failure (MTBF) when it follows an asynchronous transfer. This is because the synchronizer chain is merged with retimer-created registers, which breaks the synchronizer requirements. Without a synchronizer, an asynchronous transfer will have a very low MTBF and be reported as being unsafe.

Workaround/Fix

To work around this problem for the Intel® Quartus® Prime Pro Edition software, turn off the early retimer by writting the following assignment in the Quartus Settings file (.qsf):

"set_global_assignment -name FITTER_EARLY_RETIMING OFF" 

This problem is scheduled to be fixed in a future Intel® Quartus® Prime Pro Edition software release.