[Magic-dev] Method of storing layer information in MAGIC files

[Stefan Robert]

Ah,

this behaviour is normal and is a feature of the magic tech file.

You need to understand the concept behind the "compose" section of the 
tech file (which defines wich layers are either added or deleted when 
one is created on top of the other one) and the "cifoutput" section 
where it defines which layer are exported in gds format when you use 
the "calma" function.

Why was this behaviour chosen over retaining all layer information in 
the MAG file? Well I cannot answer this in full, but I can easily 
imagine that this can save a lot of disk space and speed-up the 
responsiveness of magic because, when you have a properly defined 
"compose" and cifoutput section, you do not need "real layer" 
information in the layout view.

It is just a matter of understanding how magic works comparatively to 
Cadence for example. Do notexpect Magic to behave like Cadence Virtuoso 
Layout (or other commercial layout tool), Magic has a different 
philosophy that has its drawbacks and advantages... and not having 
"real layer" information is not really "drawback" in Magic because 
actually "real layer" information is accessible.

Stéfan



Le 05-02-03, à 20:59, La supreme Poofias a écrit :

> Hi,
>
> I'm running in to a problem regarding the way layers are stored in 
> .MAG files. The basic problem is that certain layers drawn over other 
> layers cause the underlying layer information to be deleted.
>
> For example, if I were to draw an n-diffusion to metal1 contact, the 
> underlying information about the ndiff is deleted. That is to say, if 
> I were to erase the contact, the ndiff which was underneath the 
> contact is gone, as well. I thought I was making a mistake with 
> erasing vs. deletion, but I looked at the actual MAG files, and the 
> ndiff information was gone.
>
> To me, this seems like an inherent flaw in the file format, and it's 
> contrary with the concept of "layers." If I place a contact above a 
> diffusion, it doesn't mean that the diffusion is gone, even though I 
> can't see it anymore from the 2D overhead view. If I delete a top 
> layer, I expect the bottom layers to remain intact.
>
> I'm sure that there are quick hacks around this situation, such as 
> using the stretch and move tools, but I run in to a lot of problems 
> with those, as well (eg: one layer moves on top of another layer, and 
> then the bottom layer information seems to disappear). However, is 
> there a way to force MAGIC to retain true layer information?
>
> Regards,
>
> -K.S.
>
>
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