I used Design Compiler before and do synthesis bottom-up. Now I changed to use RTL compiler to do synthesis. I have read the user manual but I did not found how to do bottom-up synthesis using RTL compiler. Could any one tell me or show me a simple synthesis script for bottom-up synthesis?
Do you have to stick to bottom-up? From what I understand DC users do bottom-up because of capacity limitations. You should find the capacity to be higher in RC, probably allowing you to switch to top-down.
In reply to croy:
I want to how to do bottom-up synthesis using RC.
Could you please give some suggestions?
Thanks very much!
In reply to airland:
not sure what you are after. Synthesis tools do not know what you are gonig to do with the netlist so you can always use a synthesized netlist at the next level up. What are the specific of your bottom-up question ? For fast designs I would argue that Top-down traditionally yields better results. The benefits of top-down are various:
- single scripts environment to maintain
- no need to budget/guesstimate I/O delays
- better optimization of constant driven paths
This is not to say there are no benefits to running bottom up but the motivation you mention is better suited for top-down than bottom-up IMHO. In anycase, as per your original question, please clarify what aspects you are looking for and we can try to better help you
In reply to grasshopper:
Thanks for your kindly reply. I know top-down is better. I just want to know how to do bottom-up synthesis.
My question is as following:
read the whole design for one time and then use like DC's set current_design, set_dont_touch, etc. to synthesis each submodules and then synthesis the top module. For this usage we only need invoke RC license for one time; if we read one submodule, and use RC to synthesis; then read another submodule to synthesis, etc. This will invoke RC license for many times. If the license is not enough, it may be not suitable.
So I want to know whether RC support this usage (like DC to read the whole large design for one time and then synthesis each submodules/top modules with bottom-up method) or not.