maintaining the pcell structure in a gds

Hi Adhil,

Which version are you using, you didn't say?  Since you mention Stream Out (and not "XStream Out"), I will assume you are using IC5141. There is an option: "Dump Pcell Info" on the Options form for Stream Out and this will create a directory which will contain the pcell masters as SKILL, use the same options during Stream In and you should be able to perform a round-trip translation.  Look at the documentation for more detailed information (transref.pdf, pages 94 (Dump Pcell Info), 112 (Keep Pcells) 118, 124, 149).

Hope this helps!

Lawrence.

thanks man, one question, what if the pcells are already flattened into individual cells, how can we revert it back?

Hi Adhil,

It is unlikely that you can convert the new individual masters back into Pcell instances - if the Pcell instances were recorded with the parameters and their values you might be able to do it, but this could be very tricky to reverse.  So to keep Pcell instances as they are, use the Keep Pcells option.

Regards,

Lawrence.

Hi Adhil,

And even with the "keep pcells" option, the stream file still contains separate cells for each pcell variant - this is because the stream format does not have the capability to truly keep the pcells as pcells. Personally I think that the "keep pcells" idea is of dubious value, because the only use is to allow you to stream back in the stream file (essentially unaltered) provided you've kept the side file and also all the setup (PDK etc) exactly as it was at the time. It would be far better just to archive the original database alongside the stream file, and then there's no need to stream it back in again.

Andrew.

do you have some code to point me in the right direction?

Code for what?

a method to archive the database, and then to use it in a template when streaming in the gds

Adhil,

By archiving the database I mean backing it up (e.g. storing on tape, or whatever you would normally do to archive design data). The reason I've heard from customers is that they keep the GDS file and the side files produced by the "keep pcells" option in stream out so that they can restore it later (and presumably they then archive the two). But since the Cadence database contains far more the just layout data (including connectivity, schematics and symbols, models etc) you'd surely be better off archiving the whole lot when a project is finished.

There's not a means to "use it as a template when streaming in the gds" - I don't entirely understand what you mean (probably because that's not possible nor makes sense).

Regards,

Andrew.

Hi 

what i meant was to use the archived database as a reference for virtuoso, so as to use it to identify the cells which were pcells and subsequently, revert it back during streamin, provided the technology library is given. :)

 Adhil  

Adhil,

You can only do that if you used the keep pcells option (only available in IC5141 and before) when you streamed out, and then used those additional side files when streaming back in, because otherwise there's no mapping information stored which tells it what the original pcell parameters were for each variant, and what the pcell was.

If you've archived the database, there's no need to stream it back in - that's the point I was trying to make...

Regards,

Andrew.