How does TimeQuest Analysis determine Launch edge & Latch edge?

David,

I don't think I saw your second question. TimeQuest(and the fitter using TimeQuest) will try to meet your requirements. But if two clocks are asynchronous, what would a valid requirement be? Since there is no common relationship between the clocks, there is no possible delay that would satisfy all conditions. So for asynchronous clocks, the designer needs to tell TimeQuest they are asynchronous and it basically ignores them, as does the fitter. (The fitter will still try to optimize the path to use the least amount of routing as possible, so you generally get a decent fit, but it's not going to sacrifice placement/routing of a valid path to help these asynchronous paths). Asynchronous transfers are generally out of the realm of static timing analysis and up to the user to properly design for, so that the circuit can handle "any relationship" between the clocks/data and still work. An asynchronous FIFO does this. Handshaking schemes usually do this. There are other situations(like synchronizing an asynchronous signal, etc.).