How does 2-FF synchronizer ensure proper synchronization?
When multi bit signals are synchronized with 2 flip flop synchronizer, each bit is synchronized using separate 2-FF synchronizer. Metastability can cause a flip flop to settle down either to a true value or a false value. So output of every synchronizer may not settle to correct value at same clock.
What is meant by clock synchronization?
Clock synchronization is a topic in computer science and engineering that aims to coordinate otherwise independent clocks. Even when initially set accurately, real clocks will differ after some amount of time due to clock drift, caused by clocks counting time at slightly different rates.
When to use 2 flops in clock domain synchronizer?
The 2 Flops allow signal to settle down and sample it correctly without getting into Metastable State. We may also use 3 stages of D-Flops if needed but 2 D-Flops are sufficient for most of the cases. The general rule is period of destination clock should be 1.5 times of source clock period. Example below shows the 2 D-Flop Synchronizer .
When to use double flop or flip flop synchronizer?
When signals move from one clock domain to another, it may not be sampled correctly leading to unstable oscillations in the signal called metastability. Double Flop Synchronizer or Two flip-flop synchronizer is the simplest synchronization technique to ensure that the signal is sampled correctly at the destination domain.
Can a pulse be synchronized from fast clock domain to slow clock domain?
A pulse cannot be synchronized directly using 2 FF synchronizer. While synchronizing from fast clock domain to slow clock domain using 2 FF synchronizer, the pulse can be skipped which can cause the loss of pulse detection & hence subsequent circuit which depends upon it, may not function properly.
How is a pulse synchronizer used in a FPGA?
In order to synchronize data, a control pulse is generated in source clock domain when data is available at source flop. Control Pulse is then synchronized using 2 flip flop synchronizer or pulse synchronizer (Toggle or Handshake) depending on clock ratio between source and destination domain.