Is there a way or tool to characterize custom cells. I mean tools that can generate .lib and physical library.
I am not sure if tools that characterize custom cells exist, but I guess its a very hectic process when done manually. You need to change a lot of parameters (PVTs) and see how the cell reacts to them etc. Will let you know if I get any more info on the same.
Is there a tutorial or project or paper that describes the whole flow?
The complete flow would be a very elaborate one with a lot of details coming in. I haven't come across a very detailed one, but we guys did make one during my certification program. Gimme a few days, I'll dig it out for you.
how to restrict cells in P&R. That means to P&R a design with certain specific standard cells are used only.
For example if the design is of a full adder, i just want 2 input AND and OR Standard cells to be used and not XOR Standard cell.
Well for this you'll have to restrict cells to be used in your design while performing synthesis, because when you P&R your design, the tool identifies the cells present in your gate-level netlist, goes to the physical library, picks the physical data of those cells (like shape and size) and places the cell.
So, if you want to use only AND and OR cells in your full adder and not XOR cells, you should place a restriction on cells to be used while performing synthesis on your RTL netlist of your full adder. The cells to be used in your design are finalized at the synthesis stage; after that you don't have control on the type of cells in your design.
The experienced fraternity, do give your views on this. Hope what I've said is correct.