I get the following error during synthesis

ABC: Error: The network is combinational.

. Any idea how to get around it? or what might be causing it? Thanks for the help!

i would look at this issue: https://github.com/The-OpenROAD-Project/OpenLane/issues/173 i think abc tries to pass everything in as combinational unless you specify that you want things passed as sequential using -dff or something.

Thanks for the reply. In my design 2 modules are completely combinational and I need them to be that way as they are asynchronous. The other modules are sequential. So 1) would the tag -dff try passing those 2 modules as sequential? Could you please explain what that means. I am a bit confused. 2) I dont see any variables in the config.json to pass the same..or i might be missing it. Could you help me with how to pass the options? Thanks alot for the help!

I don't think there's a way to do it from the config.json file right now. I think you have to manually change the synth.tcl script..? I'm not sure though- i'm trying to figure it out myself as well. I would look here for more info about how abc does sequential vs. combinational synthesis. I'm also pretty new to these tools and the asic flow in general so I'm not sure if I even understand it correctly: https://people.eecs.berkeley.edu/~alanmi/abc/abc.htm

Thanks for the info! I myself am quite new to the flow. If I figure something out will definitely share it here too.

I don’t personally know, but the error has come up before. https://open-source-silicon.slack.com/archives/C016H8WJMBR/p1695639513619239?thread_ts=1695628555.522779&cid=C016H8WJMBR @Charly Meyer any advice?

Thank you!