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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The first two bytes of the header contain a count in eight-bit bytes of the total record length. The minimum record length is four bytes. This marks the beginning of a structure reference element a reference or “call” to another cell in the library. Required for Filtered format, and present only in Filtered Stream files.
Bit 13 flags absolute magnification. 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.
Values are 0, 3, 4, 5, and The first is “No data present”. Geometrical objects may also be tagged with “datatypes”, which can be used for any purpose, but are most commonly used to group together similarly sized objects for compensation of the proximity effect.
Max size 44 bytes. A sgream exceeding this limit will be split by default. The actual stream file: This is done by adding an additional cell to the design with the name LayerNames that contains a text elements on each layer with the layer names.
This means that any software for reading or writing GDSII has to be able to extract each byte and interpret the bits. The reason for this is as follows. These free tools include editors,    viewers,  utilities to convert the 2D layout data into common 3D formats,   utilities to convert the binary format to a human readable ASCII format  and program libraries.
PATH  No data is present. GDSII path is imported as an ADS path with square corner type resulting in the loss of data in the path’s round-ended endpoints and corners.
Seven gdzii data types are defined. gfsii
The third byte is the record type. The code is 0x Square ended paths 1: Formmat first two numbers in brackets are the record type and the last two numbers in brackets are the data type see the table above. Print version of this Book PDF file. Starts with name of the first library and is followed by the second. The following records are not supported by Stream Release 3.
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Since Advanced Design System units can be inches, microns, mils, etc. Any stram, findings, conclusions or recommendations expressed in this material are those of the author s and do not necessarily reflect the views of the National Science Foundation.
Validate File A file validation is performed after any save operation. Although the number of vertices used to approximate an arc can be controlled via the Arc Resolution dialog box see Curved Element Limitationthe vertices limit may hdsii the program gdsli correctly evaluating polygons consisting of several arcs. By activating this option via the setup dialog or via a macro, all saved GDS II files will be padded to this length by adding a 0 at the end of the file.
End of library token. However it is possible to save such large polygon in multiple blocks. Actually, the data type seems redundant, since each record forkat has only one valid data type. It won’t make a lot of sense without that background.
The fifth data type is the “Four-Byte Real”. If a character string is an odd number of bytes long it is padded with a null character. An x appears in the box to the left of s elected attributes.
B.2 Calma GDS II stream format (GDSII)
Inserting an edge is valid for GDSII output, but may be a problem for certain mask generation software. It’s simply two bytes.
This enormous base of legacy code is probably what is slowing the transition to alternatives in particular OASIS. For example, if a design contains an MLIN it will be flattened. This record must not be present if none of the fonts have gdwii textfont file.
For example, if a boundary element used a property attribute 2 with property value “metal”, and property attribute 10 with property value “property”, then the total amount of property data would be 18 bytes. Objects contained in a GDS II file are grouped by assigning numerical attributes to them including “layer number”, “datatype” or “texttype”.
All About Calma’s GDSII Stream File Format
When transferring a file via tape, the block size must be preserved. The hex numbers are read backwards, from right to left, with each pair of digits representing a byte. In an AREF the first point strezm a position which is displaced from the reference point by the inter-column spacing times the number of columns.