The Convert Menu: Data Input/Output, Format Conversion

In addition to the native cell-per-file format, Xic has interoperability with the archive file formats listed below. These file types can be read into Xic directly with the Open command, and generated with the Save As command. The Convert Menu provides for setting format-specific conversion parameters, and contains other conversion commands.

Under Unix/Linux, files are opened in 64-bit offset mode. This enables files larger than 2Gb to be processed.

Native Xic cells use a CIF-like ASCII format, with one cell per file. This is the default format used by Xic, but is not particularly efficient with respect to input/output speed and disk space.

In addition to the native cell-per-file format, Xic supports a number of archive formats, which can contain one or more cell descriptions.

GDSII
The GDSII (Stream) format is an industry-standard binary file format for cell hierarchies and libraries. Xic can read Format Release 3-7 files, and write either Format Release 7 or Format Release 3 (which is readable on systems supporting Format Release 3-7). GDSII files that have been compressed with the GNU gzip program or equivalent can be read directly, and similarly compressed GDSII output can be generated by Xic.

The GDSII directives absolute magnification, absolute angle, and absolute path width are not supported in Xic. If found in input, the values are taken as relative, and a warning is issued. These are not supported by other file formats in a portable way, and should be considered obsolete.

CGX
The CGX (Computer Graphics eXchange) format is a public-domain binary archive format developed by Whiteley Research Inc. Similar in structure to GDSII, the advantages are more efficient data representation for reduced file size and ease of parsing for faster read/write. Although presently available only in Whiteley Research products, it is anticipated that the format will eventually be supported by other vendors. CGX files that have been compressed with the GNU gzip program or equivalent can be read directly, and similarly compressed CGX output can be generated by Xic.

OASIS
The Open Artwork System Interchange Standard (OASIS) is a new standard for mask layout data being developed by the SEMI organization. This is a binary format which features more compact representation and thus smaller files than GDSII.

More information is available from wrcad.com/oasis.

The present status of OASIS support in Xic is complete:

1. Xic can read any spec-conforming OASIS file.
2. OASIS output from Xic is readable by any other spec-conforming tool.
3. Exceptions to the above are bugs, please report!

Although it is ``not documented'', Xic can directly read OASIS files that have been compressed with the gzip program or equivalent. Unlike for GDSII files, this is not really supported, and it is not possible to write gzipped OASIS output from Xic. It is preferable to use the compression provided in the OASIS format.

CIF
The CIF format, though a bit archaic, is still popular. Xic supports a number of selectable dialects and extensions.

If the input file is in CIF format, and symbol (cell) names are not provided (i.e., no symbol name extension is found), the generated symbol names will be ``SymbolN'', where N is the integer symbol number given in the CIF file.

In general, files produced with this Xic release are NOT compatible with pre-Xic-4.0 releases.

The native cell files and CIF now accept and generate arbitrarily long layer names. These are not compatible with traditional CIF, or with older Xic releases. Older Xic releases will fail to read native cell files, or CIF files, with non-traditional layer names. Traditional CIF layer names contain four characters or fewer.

Native cell files and CIF files from the 4.0 branch that use traditional CIF layer names should be backward compatible in this respect.

There is a new syntax used for electrical node property strings. This will, in general, prevent backwards compatibility of schematic files. If the Out32nodes variable is set, files written will use the old node syntax, with loss of some data that is not supported by the older syntax, but files will be readable by older Xic programs.

The Convert Menu entry brings up a menu containing commands which perform explicit translations and other manipulations and diagnostics.

The table below lists the commands found in the Convert Menu, and gives the internal name and a brief description.

Convert Menu
Label	Name	Pop-up	Function
Export Cell Data	exprt	Export Control	Create a cell data file
Import Cell Data	imprt	Import Control	Read a cell data file
Format Conversion	convt	Format Conversion	Direct file-to-file format conversions
Assemble Layout	assem	Layout File Merge Tool	Merge layout data
Compare Layouts	diff	Compare Layouts	Find differences between layouts
Cut and Export	cut	Export Control	Write out part of a layout
Text Editor	txted	Text Editor	Text edit cell file

The Open command in the File menu can be used directly to read files in the supported formats for editing. When a cell is written to disk, it is by default written in the format of origin, though a format change can be coerced in the Save As command by supplying a file extension. Thus, there are alternatives to using many of the commands in the Convert Menu.

During a conversion, a log file is written by the converters. This file contains a record of messages emitted during the conversion. If during a conversion an error or warning message is emitted, a file browsing window containing the log file will appear when the conversion is complete, though this can be suppressed by setting the NoPopUpLog variable. These messages also appear on the prompt line during the conversion. The file browser is a read-only version of the text editor window, and has a number of associated keyboard commands, including word searching. See 3.13.2 for a listing of these commands.

On GDSII and OASIS input, if there is no specified mapping for a given layer and datatype, an attempt is made to map to the existing Xic layers, and if that fails, a new layer is created.

When reading CIF, layer names are matched to those defined in the current technology in a case-insensitive mode. This differs from native and CGX file types, which use case-sensitive matching. Layers found in the file which do not match any in the technology are created, using default parameters.