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GDSII is like Gerber for PCBs. It is a format that ASIC Foundries accept for the manufacture of ASICs/VLSIs (mainly standard cells).
Alike Gerber, GDSII contains Masks layers (as many as 24 to 30), including Metal top layer(s).
The Term RTL-to-GDSII refers to a design methodoly where already in the RTL stage, route problems, critical placements, Signal Integristy, Crosstalk, and other DRCs are taken under account to shorten up the "Timing Closure" cycle process.
This is especially true for the new nanometer technologies (below 0.13um)
This is a VERY short nutshell. Hope this helps....
GDSII has been used to transfer physical design data for decades.
Due to inefficiencies in the GDSII format, the best hierarchical processing applications were handicapped at output time; with the new format the differences in data handling efficiency of hierarchical EDA application software will become even more obvious.
Mentor Graphics Corporation plans to support the GDSII replacement format in the Mentor Graphics® Calibre® product family and the IC Station® tool suite in commercial release as soon as the first quarter of 2003.
Testing shows up to 10-50 times reductions in hierarchical data volume from GDSII, and up to two or more times reduction in flat data volume from MEBES mode5 format.
Mentor agreed to hand off all proprietary rights to ...
It contains a hierarchy of structures, each structure containing elements situated on layers. It is a binary format that is platform independent, because it uses internally defined formats for its data types.
The pattern data is considered to be contained in a library of cells. Cells may contain geometrical objects such as polygons (boundaries), paths, and other cells. Objects in the cell are assigned to layers of the design. Different layers typically represent different processing steps for exposure on separate mask plates. 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.
The GDS-II format specification limits the number of vertices per polygon (boundary) and wire (path) to not more than 200 pairs of coordinates. However, many packages, including LinkCAD, can read up to the technical maximum of 32,766 coordinate pairs. By default, when exporting to GDS-II, LinkCAD will not write more than 200 vertices and larger polygons and wires are split into fragments. You may remove this limitation in the GDS-II export options.
From what I know its the standard industrial format that holding the layout cells data in binary form that founded by Calma. Its is also called Stream format. Normally the files can be ended with formats (.stm, .gds, gdsii). There exist other formats like CIF from Caltech, Oasis by SEMI (Correct me if I am wrong), and others... All other giants EDA firms like do have their own formats like Cadence, Sypnosis.. all have their own...
Why do they call it GDS-II .. is it somethin like II binary version or what is it exatly.. i know its graphic design standard. i know it contains metal layer information includin mos layers!! till layer (12-20) - this is what most people know .. i want to know beyond it!!!
GDSII Stream format is the standard file format for transfering/archiving 2D graphical design data. It contains a hiearchy of structures, each structure containing elements (boundary/polygon, path/polyline, text,box, structure references, structure array references). The elements are situated on layers. It is a binary format that is platform independent, because it uses internally defined formats for its data types. While reading GDSII files, the GDSII internal data types (like reals, integers etc.) need to be converted to the platform/CAE package datatypes that are used.The GDSII format is a sequential list of records, each record contains a header to tell what information is in the record.The order of the record needs to be according to the GDSII BNF, because of this strict organization it is relativly easy to parse. The maximum number of vertixes is officially only 200 x,y pairs, but many packages can read up to the absolute maximum of 64k/2=32k, simple because this is the maximum record lenght that can be specified (two bytes).The format is hard to read, since it is binary, for that viewers are available to view (boolean) the contents as ASCII. Also an ASCII format has been developed (KEY format) which is more than just a text representation. It is possible to convert GDSIIformat to KEYformat and back. KEYformat has extended the basic primitives to contain cicrles, arcs, polygons/polylines with arc segments.