This article explains in detail why two-FF synchronizers can help prevent metastability from propagating and resolve CDC issues in digital IC design . As explained in this article , the main problem with Clock Domain Crossing ( CDC ) is metastability due to setup or hold time violations of asynchronous crossing signals when capturing by the destination clock domain, in which the metastable state can propagate throughout the design causing data loss and even chip malfunction. Metastability in CDC design is not preventable, but synchronizers can be employed to avoid the propagation of the metastable state; hence, prevent system failures. How can two-FF synchronizers prevent metastability from propagating? As explained in this article and also shown in the waveform above, when the first flip-flop (FF) data input violates the setup or hold time requirements, the output A/B becomes metastable. However, after an unpredictable delay (Tco), the FF output would settle to a stable logi