Re: Creating transistor nodes with multicut rules in Electric tech. editor

[Steven Rubin]

> I've been working on creating an Electric technology library so it can be
> used for full-custom designs for our chosen foundry. Largely I have had no
> problems and have successfully extracted and DRC-checked Electric's GDS-II
> output with third-party tools.
>
> The problem I now have is that I can't make nMOS and pMOS transistor
> primitives where a varying number of Active-Metal1 contacts are inserted
> as the transistor is made wider. As far as I can determine, the Electric
> technology compiler does not seem to determine multicut rules for
> transistor primitives. The 'mocmos' technology source file provides
> additional C routines to allow it to do this for the
> '*-Scalable-Transistor' primitives.
>
> Can Electric's technology editor derive multicut rules for transistors?
>
> I have tried numerous examples, for instance:
>   http://www.cl.cam.ac.uk/users/afw27/transient/scalable.gif
> In every case I have tried converting the library into a technology
> Electric has either complained about unassociated contacts, differing
> number of contacts in the examples or failed to infer the rule.
>
> What I would ideally like to do is to instantiate an nMOS primitive and
> then change the width from, say, 100 to 1000 units, and have Electric
> automatically add more contacts. Is this possible just using the
> technology editor to create the technology library?
>
> If not, does this mean I have to integrate the mocmos
> 'Scalable-Transistor' code into the dumped C code of the technology
> library I have built, or can anyone offer an easier way of doing this?

Electric's technology editor cannot ever be as powerful as the C code that 
it generates.  You are right: the current version does not understand the 
"scalable-transistor" primitives of the "mocmos" technology.  That means 
you cannot build contacts into a transistor and expect it to 
understand.  This is why it all boils down to code in the end: there are 
many special-cases that only hand-coding can solve.

One alternative to hand-editing the results of tech-edit is to enhance the 
technology editor itself.  However, one look at that code will convince you 
that it is easier to use the "scalable transistor" code in "mocmos.c".

   -Steven Rubin