Magic Tutorial #9: Format Conversion for CIF and CalmaJohn OusterhoutComputer Science DivisionElectrical Engineering and Computer SciencesUniversity of CaliforniaBerkeley, CA 94720(Updated by others, too.)This tutorial corresponds to Magic version 7.Tutorials to read first:Magic Tutorial #1: Getting StartedMagic Tutorial #2: Basic Painting and SelectionMagic Tutorial #4: Cell HierarchiesCommands introduced in this tutorial::calma, :cifMacros introduced in this tutorial:(None)1 BasicsCIF (Caltech Intermediate Form) and Calma Stream Format are standard layout description lan-guages used to transfer mask-level layouts between organizations and design tools. This tutorialdescribes how Magic can be used to read and write files in CIF and Stream formats. The version ofCIF that Magic supports is CIF 2.0; it is the most popular layout language in the university designcommunity. The Calma format that Magic supports is GDS II Stream format, version 3.0, corre-sponding to GDS II Release 5.1. This is probably the most popular layout description language forthe industrial design community.To write out a CIF file, place the cursor over a layout window and type the command–1–September 26, 2001 Magic Tutorial #9: Format Conversion for CIF and Calma:cifThis will generate a CIF file called name.cif, where name is the name of the root cell in thewindow. The CIF file will contain a description of the entire cell hierarchy in that window. If youwish to use a name different from the root cell, type the command:cif write fileThis will store the CIF in file.cif. Start Magic up to edit tut9a and generate CIF for that cell.The CIF file will be in ASCII format, so you can use Unix commands like more and vi to see whatit contains.To read a CIF file into Magic, place the cursor over a layout window and type the command:cif read fileThis will read the file file.cif (which must be in CIF format), generate Magic cells for thehierarchy described in the file, make the entire hierarchy a subcell of the edit cell, and run thedesign-rule checker to verify everything read from the file. Information in the top-level cell (usuallyjust a call on the “main” cell of the layout) will be placed into the edit cell. Start Magic up afreshand read in tut9a.cif, which you created above. It will be easier if you always read CIF whenMagic has just been started up: if some of the cells already exist, the CIF reader will not overwritethem, but will instead use numbers for cell names.To read and write Stream-format files, use the commands :calma read and :calma, respec-tively. These commands have the same effect as the CIF commands, except that they operate onfiles with .strm extensions. Stream is a binary format, so you can’t examine .strm files with a texteditor.Stream files do not identify a top-level cell, so you won’t see anything on the screen afteryou’ve used the :calma read command. You’ll have to use the :load command to look at the cellsyou read. However, if Magic was used to write the Calma file being read, the library name reportedby the :calma read command is the same as the name of the root cell for that library.Also, Calma format places some limitations on the names of cells: they can only containalphanumeric characters, “$”, and “ ”, and can be at most 32 characters long. If the name of a celldoes not meet these limitations, :calma write converts it to a unique name of the form n, wheren is a small integer. To avoid any possible conflicts, you should avoid using names like these foryour own cells.You shouldn’t need to know much more than what’s above in order to read and write CIF andStream. The sections below describe the different styles of CIF/Calma that Magic can generate andthe limitations of the CIF/Calma facilities (you may have noticed that when you wrote and readCIF above you didn’t quite get back what you started with; Section 3 describes the differences thatcan occur). Although the discussion mentions only CIF, the same features and problems apply toCalma.2 StylesMagic usually knows several different ways to generate CIF/Calma from a given layout. Each ofthese ways is called a style. Different styles can be used to handle different fabrication facilities,–2–Magic Tutorial #9: Format Conversion for CIF and Calma September 26, 2001which may differ in the names they use for layers or in the exact mask set required for fabrication.Different styles can be also used to write out CIF/Calma with slightly different feature sizes ordesign rules. CIF/Calma styles are described in the technology file that Magic reads when it startsup; the exact number and nature of the styles is determined by whoever wrote your technology file.There are separate styles for reading and writing CIF/Calma; at any given time, there is one currentinput style and one current output style.The standard SCMOS technology file provides an example of how different styles can be used.Start up Magic with the SCMOS technology (magic -Tscmos). Then type the commands:cif ostyle:cif istyleThe first command will print out a list of all the styles in which Magic can write CIF/Calma (inthis technology) and the second command prints out the styles in which Magic can read CIF/Calma.You use the :cif command to change the current styles, but the styles are used for both CIF andCalma format conversion. The SCMOS technology file provides several output styles. The ini-tial (default) style for writing CIF is lambda=1.0(gen). This style generates mask layers for theMOSIS scalable CMOS process, where each Magic unit corresponds to 1 micron and both wellpolarities are generated. See the technology manual for more information on the various styles thatare available. You can change the output style with the command:cif ostyle newStylewhere newStyle is the new style you’d like to use for output. After this command, any futureCIF or Calma files will be generated with the new style. The :cif istyle command can be used inthe same way to see the available styles for reading CIF and to change the current style.Each style has a specific scalefactor; you can’t use a particular style with a different scalefactor.To change the scalefactor, you’ll have to edit the appropriate style in the cifinput or cifoutputsection of the technology file. This process is described in “Magic Maintainer’s Manual #2: TheTechnology File.”3 RoundingThe units used for coordinates in Magic are generally different from those in CIF files. In Magic,most