Intel® Quartus® Prime Standard Edition User Guide: Design Recommendations

ID 683323
Date 9/24/2018
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3.1. Metastability Analysis in the Intel® Quartus® Prime Software

When a signal transfers between circuitry in unrelated or asynchronous clock domains, the first register in the new clock domain acts as a synchronization register.

To minimize the failures due to metastability in asynchronous signal transfers, circuit designers typically use a sequence of registers (a synchronization register chain or synchronizer) in the destination clock domain to resynchronize the signal to the new clock domain and allow additional time for a potentially metastable signal to resolve to a known value. Designers commonly use two registers to synchronize a new signal, but a standard of three registers provides better metastability protection.

The timing analyzer can analyze and report the MTBF for each identified synchronizer that meets its timing requirements, and can generate an estimate of the overall design MTBF. The software uses this information to optimize the design MTBF, and you can use this information to determine whether your design requires longer synchronizer chains.