In the design of integrated circuits, the most popular format for interchange is the Calma GDS II stream format (GDS II is a trademark of Calma Company, a wholly . Portions of the GDSII Stream Format Manual, Documentation No. B97E, Feb. , reprinted with permission of Cadence Design Systems, Inc., River. GDS II is a database file format which is the de facto industry standard for . The GDSII or Stream file format stores its information in records.
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Possible types and values are: The third byte of the header is the formay type also known as a “token”. The next record begins immediately after the last byte included in the count. Exactly 1 pair SREF: GDSII specifications state that the first number should typically be set to less than 1. Path and boundary elements may have up to pairs of coordinates.
The third byte is the record type. This appendix omits the description of tape formatting, since disk files and disk file images on tape and other media are now the norm . When Holes As Polygons is not selected, polygons with holes are translated as single-segment polygons, the false edge segment becoming part of the polygon.
GDS II (Calma GDS II)
Contains four bytes which specify in database units the extension of a path outline beyond the first point of the path. Any opinions, findings, conclusions or recommendations expressed in this material are those of the author s and do not necessarily reflect the gormat of the National Science Foundation.
An array of coordinates in data base units. It is an integer between and This is another artifact of the 16 bit words that the stream file format assumes. The following is a list of record types. These elements are further defined in the Stream syntax list.
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For example, if a design contains an MLIN it will be flattened. The representation of negative numbers is the same as that of positive numbers, except that the highest order bit is 1, not 0. It is a binary file format representing planar geometric shapes, text labels, and other information about the layout in hierarchical form. GDSII files were originally placed on magnetic tapes.
This informationis used only when reading the data into a new library. The third point locates a position which is displaced from the reference point by the inter-row spacing times the number of rows.
I’ve noticed that some OK, many stream files that were originally written to disk using more modern software also pad the file to a multiple of bytes using NULL characters.
The records shown within square brackets ‘’ are optional. Different layers typically represent different processing steps for exposure on separate mask plates.
The names of the layers and its stram in the design is not stored. This limit can be set via the setup dialog or via a macro. In the MASK list, data types are separated from the layers witha semicolon.
The first is the number of columns. Lack of Support for Holes Lack of support for holes is usually not a problem, but should be considered. Note Because the GDSII stream is a block-structured binary file, it can easily be corrupted when transferring the file from one system to another. The value of the text type must ge in the range of 0 to For,at name is padded with nulls if it is shorter than 44 bytes.
GDSII Stream File Translator
The value must be from 0 to There may be from 1 to 32 ACL entries, each consisting of a group number, a user number, and access rights. If memory serves, Calma DOS allowed 6 characters in a file name, with a 2 character extension.
GDS II files can be read as normal files or gzip compressed files without an external decompresser. The hex numbers fogmat read backwards, from right to left, with each pair of digits representing a byte. Retrieved from ” https: Unfortunately, when one needs to compute the actual position of the polygonal entities, one must “reverse” this nesting; for large databases this turns out to be a difficult computation to do quickly.
The first two words, or four bytes, are called the “Record Header” A record can be as small as 4 bytes long.
Maximum length is characters. To calculate the size of a user unit in meters, divide the second number by the first. Fortunately, the way the database was created enabled users to extend many of the dejure limitations while maintaining defacto compatibility with the actual architectural underpinnings.