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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It won’t make a lot of sense without that background. It is a binary file format representing planar geometric shapes, text labels, and other information about the layout in hierarchical form.
I’ve listed the essential ones here:. The pattern data is considered to be contained in a “library” of “cells”.
CHAPTER 1 GDSII format
NODE  No data is present. GDSII files were originally placed on magnetic tapes. For an 8-byte real, the mantissa is in bits 8 to Since Advanced Design System units can be inches, microns, mils, etc.
Each name is padded with nulls if it is shorter than 44 bytes. For every hex digit shifted, the exponent is decreased by one. The Advanced Design System reads GDSII files into a layout design without circuit or schematic information, internally converting the drawing data to the current layout units. Applies to pathtype 4. While these attributes were designed to correspond to the “layers of material” used in manufacturing an integrated circuit, their meaning rapidly became more abstract to reflect the way that the physical layout is designed.
Real numbers are not represented in IEEE format. One or more Stream records 3. The size, in layout units, fomat the text in the exported design. There are values for such things as the beginning of a structure, the beginning of a boundary, the end of a structure, and so on.
There may be more than one piece of data, but the rest of the record will be of this type. GDSII interpreters will either impose such a limit strea, or will impose an implicit limit by running out of memory during recursive operations.
The name of font 0 starts the record, followed by the remaining 3 fonts.
GDSII – LayoutEditor Wiki
The GDSII Stream format manual says that a record may be infinitely long, but frankly, I don’t see how it can get over bytes long, since the first two bytes of the record header are an unsigned integer that defines the length of the record. 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 prevent the program from correctly evaluating polygons consisting of several arcs.
GDSII is divided into “records. The database is binary for compactness. In some cases, this name does not match that of the imported file.
An element shown in lower case means that name can be further broken down in to a set of record types.
If memory serves, Calma DOS allowed 6 characters in a file name, with a 2 character extension. In database units, may be negative. When Flatten Components is selected, all instances whose artwork type is defined with an AEL macro will be flattened when exported.
GDS II (Calma GDS II)
It is stored in twos complement format, with the most significant byte first. If it is set, then reflection about the X axis is applied before angular rotation. Currently, the format is owned by Cadence Design Systems.
The fourth byte of the header describes the type of data contained within the record see table below. The 7 least significant bits of the first byte are the exponent in “excess 64” notation. Fromdefault is 3. Values are 0, 3, 4, 5, and The default value is 1. The GDSII specification includes the description of 69 different record types, but less than the half are normally used.
For example, if a design contains an MLIN it will be flattened. Therefore, some consideration should be given to the use of curved elements and the extensive use of arcs and circles in your layout design.
The string must adhere to CDOS file name conventions for length and valid characters, and may contain file extensions such as “. The attribute-value pairs associated with any one element must all have distinct attribute numbers. It is an integer between and An x appears in the box to the left of s elected attributes.
Valid values are 1 – inclusive. To calculate the size of a user fprmat in meters, divide the second number by the first. Improvements and Enhancements since ?
I’ll show the subtraction in the formula below. For AREFs, the entire array lattice is reflected, with the individual array elements riidly attached.
The reference library names may include directory specifiers separated with “: The value must be from 0 to