Asynchronous Clock Pulse Synchronizer

Asynchronous signal lt Synchronizer clock period Similar to the circuit above, this synchronizer is typically put into a special library cell to keep the The input signal of a pulse synchronizer is a single clockwide pulse that triggers a toggle circuit in the originating clock. The output of the toggle circuit switches from high to low and

It consists of two flip-flops that operate in asynchronous clock domains, mitigating the risk of metastability. The first flip-flop captures the incoming signal, while the second flip-flop stabilizes the signal and ensures reliable transmission to the destination clock domain. The Pulse Synchronizer is a powerful technique that ensures the

In an asynchronous clock domain crossing CDC, where the source and destination clocks have no frequency relationship, a signal from the source domain has a non-zero probability of changing within the setup or hold time of a destination flip-flop it drives. A toggle synchronizer which has a pulse to level converter at the source side and

that has transitions synchronized to a local or sample clock.quot The most common synchronizer used by digital designers is a two-flip-flop synchronizer as shown in Figure 3. SNUG San Jose 2001 Synthesis and Scripting Techniques for Rev 1.2 Designing Multi-Asynchronous Clock Designs 4 aclk bclk dat adat bdat1 bdat2 adat bdat1 bdat2 aclk bclk quot0

PulseToggle Synchronizer. Consider a simple togglepulse synchronizer like this credits edn.com For this pulse synchronizer to work correctly, the output signal from flop-A has to be stable for a minimum time period such that there is at least one clock edge at destination clock that will sample the data correctly without metastability

Clock 1 is considered the synchronous clock and clock 2 is the asynchronous clock. They have simulated frequencies of 100 MHz and 59 MHz respectively. Observe that sync_out follows the in signal by three rising edges of clk_1. It's as if sync_out is a replica albeit a delayed replica that is stretched to by 3 rising edges of clk_1.

f sampling clock frequency a asynchronous event frequency For a typical .25um ASIC library FF t 0.31ns T o 9.6as t r 2.3ns For f 100MHz, a 1MHz Traditional synchronizer n SIG is asynchronous, and META might go metastable from time to time n However, as long as META resolves before the

Next one is a bit tricky one how to synchronise a pulse from one clock domain to the other? Two-flop synchoniser fails miserably when passing a pulse from fast clock to slow clock. Native Pulse synchroniser works well but has chances of missing pulses, if generated at consecutive cycles. So handshake-based pulse synchroniser is preferred.

period of the synchronizer clock plus the required hold time of the first synchro-nizer flip-flop. The safest pulse width is twice the synchronizer clock period.This synchronizer does not work if the input is a single clockwide pulse entering a slow-er clock domain however, the pulse syn-chronizer solves this problem. The input signal of a

Pulse synchronizer. In handshake based pulse synchronizer, as shown in Figure 5 and Figure 6, synchronization of a pulse generated into source clock domain is guaranteed into destination clock domain by providing an acknowledgement. There is one restriction in pulse synchronizer that back to back one clock gap pulses cannot be handled.