in which of the following double synchronization is not possible,when two clocks clkA and clkB are used
where
clkA - source clock
clkB- destination clock
1.clk A has greater freq than clk B
2.clk A has less freq than clk B
3.clk A has double freq than clk B
4.both have same freq but they are asynch to each other
U can use double synchronisation for clocks from lower to higher frequency but not the other way around. Have to be careful here while analyzing so that u don't loose any data.
As the u will loose the data if its higher to lower frequency. In this case u need to design FIFO after calculating the depth.
If the clocks have same freq but r asynch then u need to know the phase diff.
You can use double synchronization between any clocks just that you need to make sure that you have data stable from source domain to be sampled in Destination domain.