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From: R. Timothy Edwards (tim AT stravinsky DOT jhuapl.edu)
Date: Mon Apr 21 2003 - 13:12:27 EDT

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    Dear Charles,

> I am assuming myself by studying some magic features that I havent looked at
> before in the latest magic-7.2.36 file. I suspect my issues are my
> understanding and not a magic issue. Heres the situation. I have a modest
> inverter magic file created with the default technology. I can do a 'cif
> write invlay.cif' followed by a 'cif read invlay.cif' and I see two off grid
> errors for a file that was created with the same technology. The off grid
> errors are reffering to the GND and Vdd lines in my file at the top and
> bottom of the inverter and they are:
> 
> 94 GND 0 -90 CMF;
> 94 Gdd 0 90 CMF;
> 
> Magic is saying that they are off the lambda grid by 1/2 and are snapped to
> grid. I would expect them to be the same as they were both created by magic
> with the same technology file.

Possibly I screwed up something with regard to CIF input, as I haven't seen
anything like this, but then I usually make minimal use of labels, and I'm 
not sure if I have tried writing/reading back labels from CIF/GDS recently.
I did muck with the code recently, though.  You didn't say whether the
labels ended up in the right place because it could be a read error but it
could also be simply that it was not supposed to print the warning message
there.

> If I subsequently say, 'gds write invlay.gds; followed by 'gds read
> invlay.gds', magic says : "Reading invlay", then "Reading XXXXX1" and the
> screen is now blank. I really dont know what the XXXXX1 is referring to and
> I am puzzled why the screen is blank.

GDS files do not define a "top level" cell like CIF does.  In GDS, all layout
is defined inside cells, including whatever is on top.  So the usual
procedure for reading GDS is to follow the read by doing "cellname top" to
see what cell or cells are at the top level of the hierarchy.  The "cell
view" window is helpful for doing this, in the GUI-wrapped version of the
Tcl-based 7.2.  In this case, though, you know what your top-level cell
is (invlay), so after the GDS read, you should be able to do "load invlay"
to get the invlay cell back in the layout window as the edit cell.

					Regards,
					Tim

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