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From: R. Timothy Edwards (tim AT stravinsky DOT jhuapl.edu)
Date: Wed Jan 02 2002 - 16:54:24 EST

  • Next message: Jeff W. Sondeen: "Re: CIF and nanometers" 

    Dear Magic Hackers (esp. Jeff Sondeen and Philippe Pouliquen):

   There were some email posts to the magic-dev group a while back about the
implementation of the "nanometers" keyword in the cifoutput section of the
magic techfile.  As I recall, Philippe argued that the 1 centimicron limitation
was not a limitation of the CIF spec, per se, because the DS command can
always be specified with a scale divisor such that "DS 0 1 10" would
effectively put all measurements in nanometers, assuming all prior scaling
is 1:1.  If so, then to deal with tech feature sizes like 0.13 um, the
cifoutput section should really allow a "scale expander" in addition to
the "scale reducer", so the CIF output file can make use of this scale
expander instead of having a scale expander fixed at 2.  "scale" values
which are odd numbers in the cifoutput section would automatically
cause both the scale and the expander to be doubled (so box centers still
fall on integer boundaries).  "nanometers" would effectively be a 
shorthand for a scale expander of 10.  "calmaonly" would be unnecessary,
and would do nothing.

   The real question, then, is whether any CIF readers (especially MOSIS)
make an implicit assumption about minimum CIF values being integer
centimicrons, or whether they follow the spec to the letter and allow
any scaling.  I know that MOSIS rounds off, such as the TSMC 0.25 um
process becomes a 0.24 um process in the CIF output sent to MOSIS, and
I presume that MOSIS scales it by a factor of 25/24 before passing it
on to the vendor.  How would MOSIS handle a CIF file that used a scale
expander to exactly represent lambda=0.125?  Would the CIF file parser
hiccup and die, or would it actually take the input as written?  (Jeff,
can you answer this question?)

   If MOSIS can handle sub-centimicron measurements in CIF, I intend
to rewrite the CIF section to take a scale expander from the tech file
and generate output accordingly, as outlined above.  Suggestions,
please?

						Regards,
						Tim

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