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From: Philippe O. Pouliquen (philippe AT alpha DOT ece.jhu.edu) Date: Fri Mar 30 2001 - 09:48:32 EST
Mikael Sahrling <mikael AT mta5 DOT snfc21.pbi.net> wrote: > > Jeff W. Sondeen <sondeen AT rcf-fs DOT usc.edu> wrote: >> >> Mikael Sahrling <mikael AT mta5 DOT snfc21.pbi.net> wrote: >>> >>> 2) input/output stream. One of the technologies we're working with >>> have a grid-size of 0.025 microns. This will not work with the >>> cifinput/output scale of centimicrons. Yes it will. CIF does not currently prohibit dimensions smaller than 1 centimicron. You specify the scale in the CIF DS statement, where a 1-to-1 scale would result in units of 1 centimicron. >>> Instead I changed the cif/calma source code to support millimicrons >>> instead. My suggestion is to change the scale to millimicrons. No! Don't do that! Your CIF files will be non-standard! >> however, my understanding is that CIF format by definition must be in >> a scale of .01um. also, calma (GDS) is supposed to be .001 um but i >> think that's a convention. Hardly a convention, its the *definition* > This could be, I always use calma format ... . If this is true the > technology we're using (0.025 microns grid) is incompatible with CIF. > Maybe one could have a setting such that if calmaonly is used in the > cifinput/output section the scale is in millimicrons ... ? When you describe a physical object, you have to specify the unit of length. For convenience, the default unit is 1 centimicron for CIF, and 1 millimicron for GDS/CALMA. Otherwise, the CIF/GDS interpreters would have to recognize all sorts of units (meters, feet, inches, mils, furlongs :-). It is true that historically, Magic has prohibited the use of CIF when lambda is not an even integer number of centimicrons. I believe that this may be due to an early definition of CIF prohibiting features smaller than 1 centimicron (coupled with Magic contact placement), or perhaps an early version of the DS statement didn't have a denominator. Maybe somebody with a copy of Mead & Conway can check on this. In any case, other layout tools (e.g. Tanner L-Edit) happily produce CIF with arbitrary ratios of lambda to centimicrons, and these CIF files are handled without incident by MOSIS (for instance). Philippe Pouliquen The Johns Hopkins University
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