Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
Consider the domain as a sub-circuit. So if a part of your circuit is running at X Mhz and the other part is running at Y Mhz(X not equal to Y) and they both want to exchange data then it is considered a case of cross clock domains. Problems like metastability starts to creep up.