During ECO process, i have to add a few flops. However i don't know which level of the clock tree these flops have to be connected?
Is there a way by which the tool automatically detects/connects these flops to the corresponding clock tree and not affect the skew and still meet the timing?
Are there any guidelines as to how to perform clock ECOs for the newly added flops?
It sounds like these flops don't already exist in the design as spares (which would already be connected to the clock tree). If you are just adding them now, you'll have to decide exactly where on the clock tree you want to connect them. This will depend on what else this new flop talks to. You probably want to place it on either the branch of your clock tree that has the flops the new flop talks to, or a branch with similar skew, if it's not too far away. A lot depends on your floorplan, too, and where you have room to place these new flops. It's possible that you'll have to do another timing opt to fix any timing violations after you get this new logic in.
Thanks for your suggestions.
Since the changed netlist comes from FrontEnd they are unaware of the physical attributes, like placement. During the eco process, it is possible to place them in an appropriate location using ecoPlace and/or other commands in order to satisfy their timing requirements. However the only missing part is the connection of the clock pin of the flop to the appropriate level in the clock tree.The netlist might tie the CK pin of the flop to the module/main CLK.
There are other tools in the industry which automatically identifies the level in the clock tree to which the newly added flops are to be connected to meet the timing requirements. This feature is part of incremental/eco CTS. Hence was wondering if there's a way to accomplish the same using encounter as well.
I don't think there's a way to do this, but it sounds like a great enhancement request!
Thanks for acknowledging the request. I've already filed a CCR for the same. Hope to see this feature implemented very soon.
Could you let me know the CCR #? I'd like to track it myself - I think it's a great request and will be very useful!