Clock domain crossing

What is this clock domain crossing actually means? 

Why people show up as a big concern in constraining?

Is it a Big Fish to deal or a Normal Fish to cook.... 

... The very famous Document that everyone will have for CDC

Doc1 - http://www.sunburst-design.com/papers/CummingsSNUG2008Boston_CDC.pdf

Just follow up this site (Doc 2)- and you shall be able to get why we need a handshake methodology, for CDC.

Doc 2 - https://filebox.ece.vt.edu/~athanas/4514/ledadoc/html/pol_cdc.html

Ok, Let us start with the basic understanding from here.

When we say 2 clocks crossing; think in all possible assumptions like:

- Both the clocks may be of different/same source; they might differ in frequencies (slighter/larger).

- One thing to worry about is how we can get the data without missing?

Can we check a CDC timing check in Static Timing Analysis?

Assume that we have 2 clocks for launch and capture:

3 Major issues as we already know in CDC. 

1) Metastability            2) Data incoherence        3) Data Loss 

We use synchronizers, as given in the Doc 1 and 2, we have our problem resolved from RTL perspective.

Here we will see, how a timing report looks like?

...... to be continued.... 

Hariharan GB

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