Monster Media 1996 #15

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≡≡ Introduction Introduction TLC2GDS and GDS2TLC Conversion Utilities ---------------------------------------- LASI drawings are not very useful if they cannot be converted to a commonly used CAD format, for mask generation or for transfer to another CAD system. The most common is formally called Calma Stream Format, which is also know as GDSII (Graphic Design System II), or just GDS. Although Calma drawing systems for ICs have become pretty obsolete, the data format survives, and most pattern generators accept it, and newer CAD systems such as CADENCE or MENTOR can usually convert it. LASI can be converted to GDS Format exactly, and from GDS with some limitations. LASI has a drawing structure that is very similar to the Calma drawing system, with the exception that LASI has box objects and is more limited in its data capacity and cell nesting depth. With LASI, cells are similar to Calma structures, except that a certain rank is given to a cell. With LASI there are no Calma boundary items, instead there are zero width paths usually called poly. LASI drawings transform easily into GDS because a box can be made into a boundary, a poly can become a boundary also, a path can transform directly into a path, and cells can easily become structures. Since there can be more or less an infinite number of TLC files, a GDS file with almost any number of structures can be converted to TLC files. The TLC files can then be selectively converted into LASI drawings. Likewise, a large collection of TLC files can be selectively converted into a GDS file. TLC2GDS.EXE is a program that converts a LASI drawing in TLC file format into Calma Stream Format. The file generated by TLC2GDS may be put on magtape, or more likely, be put on a floppy disk (in MS-DOS file format) for reading by pattern generators or work stations that have MS-DOS floppy reading capability. The GDS2TLC.EXE program will read back a GDS file and will construct a LASI drawing in TLC form as best as possible. A drawing first done on LASI will reconstruct exactly if returned from another drawing system without having been modified in some non-compatible way. Drawings made originally on other systems may occasionally convert differently, since LASI presently doesn't have such things as datatypes, texttypes, arrays or layer 0. Converting TLC to GDS (TLC2GDS) Page 1 - Conversion Setup Normally run TLC2GDS.EXE in the drawing directory of the drawing to be converted. TLC2GDS will start with the Conversion Setup page. It requires the following entries: ■ Main TLC file to be Converted. This is the TLC file that contains the main cell and references to any other lesser cells that may be used in that cell. It will automatically have the extension ".TLC". ■ Name of the GDS File to Make. This is the name that you want for the stream format file. You can add an extension other than ".GDS", but if you don't add an extension, ".GDS" will be added. If you leave this entry blank, it will be given the name of the main TLC file with the extension ".GDS". ■ GDS Drawing Library Name. This is the name to be included in the converted GDS file. This is usually for reference, since many applications don't require this name. ■ Physical Units (um or mil). This is name of the units in which the drawing has been done. This can only be "um" or "mil", and will default to "um". ■ LASI Units per Phys Units. This is the scale you used in your LASI drawing. It is what was set by the SCALE command, and was written into the TLC header record when you made your TLC files. If either Physical Units or LASI Units are left blank, TLC2GDS assumes that you want it to read these from header of the Main TLC File. It will disregard both of these items from the setup and substitute what it reads in the TLC file. ■ GDS Units per Phys Unit. This is the number of basic units that you want to be written into the UNITS record of the GDS file. This number should be an INTEGRAL multiple of the LASI units. It is typically 1000 units per micron, but can vary with applications. When TLC2GDS runs, it displays a Scale Bar at the bottom of the screen. This indicates the GDS units that is being used, the LASI units that are being used and the the Rescale Ratio, which is the ratio of GDS units to LASI units. To prevent roundoff errors, the Rescale Ratio should be an INTEGER. If the Rescale Ratio is not an integer TLC2GDS will display a warning, and will convert as accurately as it can. ■ The Scale Unit LSB Correction. This needs some explanation. This allows you to modify the Least Significant Bit of the scale numbers placed in the GDS file. This is about 10e-16 of the actual scale, but some conversion software (early Cadence for instance) is fussy and requires the exact bits. This will normally be 0. If you have trouble, try +1 or -1 and see if it fixes the problem. Note: This correction is applied to all 8-byte real numbers in the stream format records. Currently this only affects the UNITS, MAGNITUDE and ANGLE records. ■ X and Y Drawing Offsets. This is the offset to be added to the placement of the main cell to be put in the GDS file. This allows you to shift your drawing in the GDS file. It is in physical units. This shift is only applied to the main cell. That is, any lesser cells that TLC2GDS also generates are not shifted, since this would cause your drawing to be hopelessly distorted. For example, you may make a LASI drawing using the whole LASI drawing area so that you use negative coordinates, but a pattern generator only accepts coordinates greater than or equal to zero, you can add offsets equal to the most negative drawing coordinates, so that all coordinates are positive. ■ Datatype to Use. This is the GDS Datatype attribute for boundaries, etc. This is a parameter that LASI doesn't use. It can be 0-63; usually 0 is used. ■ Default Line Width. This is in physical units and is the width that open polygons or lines will be given if converted to paths. It works only if you convert with the Make Only Proper Poly switch set to "N" (see below). This width might have to be set to something greater than zero for some other drawing systems to accept the figure. This value can be set to zero, but the minimum value greater than zero will be limited to two GDS basic units. This may be less than the minimum LASI path width, and therefore may not convert back (using GDS2TLC) correctly. Set this to zero if you want polygons to unchanged. ■ Sort in Ascending Rank Order. The structures in the GDS file can be sorted by ascending or descending LASI rank. Some programs that use stream format may require that the main structure (highest ranking cell) come first in the data. Enter "N" if you want structures to be sorted so that the main structure comes first in the GDS file, or "Y" if you want it to come last. ■ Convert Text. If you want to convert LASI text, set the switch to "Y". Otherwise, text will not be converted. Text conversion is somewhat confusing because GDS has several attributes for its text. This is explained below under Text Setup. ■ Convert Names to Lowercase. Some systems into which LASI can be converted use lowercase names for the Calma structure names. You can have TLC2GDS convert any cell names to lowercase by setting this parameter to "Y". Normally this will be "N". ■ Make Only Proper Poly. This permits checking for polygons that may not produce shapes with area that are normally used in an IC or PC board. If this switch is set to "Y": ∙ Boxes with any opposite sides superimposed (crushed boxes) will be removed. ∙ Polygons with more than 200 vertices (Calma limit) will be reported. ∙ Polygons with one vertex (single point) will be removed. ∙ Polygons with only two vertices (line segments) will be removed. ∙ Open polygons with more than two vertices will be closed. ∙ Acute angles in paths or poly (before and after closure) will be reported. Setting this to "N" will permit conversion of open poly figures. If the Default Line Width is set to something greater than zero: ∙ Crushed boxes will be reported but NOT removed. ∙ Single points will be removed. ∙ Line segments will be changed to paths with the default width. ∙ Polygons with more than two vertices will NOT be closed, but will be changed to paths with the default width. ∙ Acute angles will NOT be checked. If the Default Line Width is zero, only crushed boxes will be reported. ■ Relocate Layer 64 to Layer. LASI uses layers 1-64, but Calma uses 0-63. you can move anything on layer 64 to any Calma layer 0-63. Usually 0 is convenient, but you must be sure that it is an unused layer in your LASI drawing. ■ Filter Single Layer. If the GDS file is going to a pattern generator, you might want to make files that contain only one layer. You can set this number to any layer from 1 to 64. Boundaries, paths and text ONLY ON THAT LAYER will be passed. If you want to pass all layers leave this entry blank. Warning: If you intend to transfer complete drawings in GDS format, be sure that the Filter Single Layer entry is blank. ■ Report Destination. This allows you to print or save a conversion report. The parameter must be one of the printers "LPT1","LPT2","LPT3" or "PRN" (=LPT1), "FILE" for the file TLC2GDS.RPT or blank for no report. If the Report Destination is blank, and a message occurs, the program will pause and wait for a key to be pressed. Otherwise, there will be no pause and the message will be written to the report. Page 2 - Text Setup Press ALT-T or click "Text" to go to Page 2, the Text Setup Page. GDS uses several attributes to construct text. TLC2GDS can relate these to each of four LASI Text Sizes. Normally, you would assign the Font attribute to different text sizes. Notice that there are 4 fonts and 4 sizes. The attributes that you use depend on just how you want to distinguish different texts. Different applications or conversions to other CAD systems will use different attributes. Some experimentation will probably be necessary to convert text reasonably correctly. Note: If your drawing contains text with a size not defined, the text will be converted with the attributes of the next SMALLER size. For the four text sizes, first enter the text size in physical units. Then set the following parameters: ■ Font, which can be 0 to 3. This is written into the PRESENTATION record. ■ Texttype, which can be 0 to 63. This is written to the TEXTTYPE record. ■ Magnification, which can be used to change text size if the other parameters produce text of the same size. This is written to the MAG record. ■ Text Width, which is usually 0, but may have to be set greater than zero so that certain CAD systems will accept the text. This is in physical units and is limited from 0 to the size of the text. This is written to the WIDTH record. ■ Vertical Justification, which may be set to top, center and bottom (T,C or B). LASI text is always left-bottom justified so normally you will set this to bottom or "B". This is written to the GDS PRESENTATION record. LASI text will pass its orientation to the GDS text. The orientation is written into the ANGLE and STRANS records. Starting Conversion When you are happy with the setup, press ALT-G or click "Go" to start conversion. If you have previously run TLC2GDS, there will be a setup file in the drawing directory named TLC2GDS.SET. If this is found, the setup parameters will be loaded when you first run TLC2GDS, and will be stored again as you start the conversion. This saves a great deal of time when running TLC2GDS since you only have to modify any parameters. Important: It is not guaranteed that future versions of TLC2GDS or GDS2TLC will have the same SET file format. If you see obvious errors in the setup values, just erase the old SET file, run the program again and modify the default values. Errors and Warnings Most errors ar self-explaining. The warnings that TLC2GDS lists as it converts are as follows: "TLC and Setup LASI Units do not Agree" means you are changing the LASI units to something different than what is written in the header of the TLC files you are converting. This may or may not be a useful thing to do, and will generally result in an oddly sized GDS drawing. To use the TLC header units, leave Physical Unit or LASI Units per Phys Unit blank. "Resolution Lost ..." means that the Rescale Ratio was not an integer. It is possible that a LASI coordinate will not fall exactly on a GDS coordinate. Usually this is not a serious problem, because the GDS units are usually much larger than the LASI units, so only a error that is a small fraction of a LASI unit will be made. "Duplicate Vertex Removed at ..." means that more than one consecutive vertex was found at the same location in a poly or path. The extra vertex was removed in the stream file. "More that 200 Vertices at ..." means that the limit of 200 vertices in the stream format for a single boundary or path was exceeded. The boundary or path WILL NOT be truncated but will be converted to stream anyway. This may not be acceptable to other stream reading programs, but will convert back using GDS2TLC. To correct this problem, go to your layout and break up the poly into smaller closed polygons or break the path into smaller segments. "Crushed Box (Removed) at ..." means that a box with opposite sides superimposed was found (and not converted). "Single Point Removed at ..." means that a poly or path with a single vertex was found and not converted. "Acute Poly/Path Angle at ..." means that a polygon or path was found with an acute angle in it. Generally, acute angles indicate shapes that may be hard to reproduce, or polygons or paths that have been folded back on themselves. "Poly Line Segment (Removed) at ..." means that a two vertex polygon was found (and the line was not converted). "Open Poly (Closed) at ..." means that the first and last points of a polygon were not the same (and a new point was added to close the poly). "Coincident Vertices at ..." means that two or more vertices in a single poly or path were at the same location. These vertices need not be sequential. This is just a warning that the boundary or path might not be a legal figure. Note: The X=,Y= reported is always the first point of a poly or path or the lower left corner of a box. L= is the layer. Converting GDS to TLC (GDS2TLC) Page 1 - Conversion Setup Nornally run GDS2TLC.EXE in the drawing directory of the drawing to be reconstructed from stream format. GDS2TLC will start with the Conversion Setup page. It requires the following entries: ■ Name of the GDS File to Convert. The extension of the file name is arbitrary, but is usually ".GDS" or ".CSF". The name may also include a path. ■ Path (or destination) of the TLC Files to be Made. If you want the files in the current directory leave this blank. ■ Physical Unit (um or mil). This is the physical unit in which the GDS drawing has been done. This can only be "um" or "mil", and will default to "um". ■ LASI Units per Phys Unit. This is scale you intend to use in your converted LASI layout drawing. It is the same scale you set using the SCALE command when you begin a LASI drawing. ■ X and Y Drawing Offsets. These are in physical units and are to be added to the placement of the "main" cells in the TLC files. This allows you to shift the position of GDS drawings in the TLC files. This shift is only applied to cells listed in the Structures to Offset list (see below). That is, any lesser cells that GDS2TLC also generates are not shifted, since this would cause your drawing to be hopelessly distorted. ■ Accept GDS Layers. If you don't want some of the GDS layers you can filter them out. List the layers the same way that you list layers in the LASI VIEW and OPEN commands, that is, using numbers and dashes separated by spaces. For all layers just enter "-". Note that GDS layers are 0-63. ■ Accept GDS Datatypes. For all datatypes enter "-". Note that datatypes are 0-63. ■ Convert GDS Text. If you want to convert any text in the GDS file set this to "Y". ■ Check for Open Poly. GDS2TLC will compares the first and last vertices of GDS boundaries. If they are different, GDS2TLC does not close the converted polygon, but leaves it open and displays a warning message. Set this to "N" if you want to bypass this check. ■ Replace Old TLC Files. GDS2TLC checks if a TLC file is already present the destination directory. If the TLC file is present, this switch will prevent it from being rewritten. If the TLC file for a cell is missing it will always be written. ■ Clear Optional Records. This needs a little explanation. GDS elements (boundaries, paths, etc.) can have optional records in their construction (width for paths, for example). An optional record that sets a parameter may or may not appear in the stream before an element is to be made. The value of the parameter needs to default to something, which could be the parameter set by a previous record (in another element) or the parameter can default to "no effect". Most of the time set this switch to "Y", and only try "N" if there is an obvious error in the conversion. ■ Manually Rename Structures. The names of GDS structure may have come from a UNIX system that can have non-DOS names, that is, they may be longer than 8 characters and may contain characters that are illegal in MS-DOS filenames. If this is set to "N" then GDS2TLC will try to modify any illegal names by truncating from the left and removing any illegal characters. If this fails, it will ask for you to enter a new name for a structure. If you set this to "Y", GDS2TLC will immediately ask for a new name without trying to modify the name. ■ Convert Boundaries to Boxes. If the GDS file contains boundaries that have exactly 5 vertices and form a rectangle, you can convert these to LASI boxes, otherwise they will convert to 4-sided polygons. ■ Recognize CR or LF as NL. Different CAD systems may use either CR (carriage return) or LF (line feed) as indicators of a new line in their text. LASI has single line text, but GDS2TLC can break multi-line text into individual LASI text lines. ■ Relocate Layer 0 to Layer. Since LASI does not use layer 0, you must move anything on that layer to some LASI layer. Normally, this will default to 64, but you can set the layer 1 to 64. ■ Make CELLS.REF File. You can generate a list of the converted cells in a CELLS.REF file. This is the same as TLCOUT.EXE generates, and is useful if you are converting a large number of unrelated cells. This file will be made in the same directory as the TLC files. ■ Report Destination. This allows you to print or save a conversion report. The parameter must be one of the printers "LPT1", "LPT2", "LPT3" or "PRN" (=LPT1), "FILE" for the file GDS2TLC.RPT or blank for no report. If the Report Destination is blank, and a message occurs, the program will pause and wait for a key to be pressed. Otherwise, there will be no pause and the message will be written to the report. Page 2 - Text Setup Press ALT-T or click "Text" to go to Page 2, the Text Setup Page. To convert text, first set the four LASI Text Sizes in physical units. The text sizes that you set will be in multiples of smallest LASI physical scale unit. These sizes will be rounded automatically by the LASI drawing program to the actual discrete text sizes used in LASI drawings, but you may enter any size that is "close" to the size that you want. Several attributes can be used to construct text. The attributes that GDS2TLC can use are: ■ Font, which can be 0 to 3. ■ Texttype, which can be 0 to 63. ■ Magnification, which can be used to change text size if the other parameters produce text of the same size. ■ Orientation, which allows text to be rotated in 90 deg increments and be flipped. ■ Vertical Justification, which can be top, center or bottom (T,C or B). LASI text is always left-bottom justified, but if center or top justification is found in the GDS file, a displacement will be added to the position of the LASI text. ■ Horizontal Justification is always changed to left. You can relate the four LASI Text Sizes to either Font or Texttype. Font is given first priority. Setting Font or Texttype to "-" causes that attribute to be ignored. Setting both to "-" defaults to minimum size, but still converts text. If you use Magnification, the text size will be further magnified by the MAG records found in the GDS file. If not set, magnification will be 1.0. If you use Orientation, the text will be rotated and flipped by the the ANGLE and STRANS records. If not set, text will be angle 0 and unflipped. If you use Justification, the text will be moved vertically as if the text's reference point was at the top, center or bottom of the text using the information in the PRESENTATION records. Some experimentation will probably be necessary to convert text reasonably correctly. Page 3 - Structures Setup Press ALT-S or click "Struct" to go to Page 3, the Structures Setup Page. There are two lists on this page: ■ Structures to Omit. Enter the names of any GDS structures that you don't want to be converted. GDS2TLC will simply read over these structures and not produce any TLC files. ■ Structures to Offset. GDS2TLC will add the offset that you set on the first setup page (above) to the placements of cells, boxes, paths and text in the listed structures when they convert to TLC. This allows you to move LASI cells to better locations. For example, you may get a GDS drawing made for a pattern generator that only accepts coordinates greater than or equal to zero, you can add negative offsets to the drawing coordinates so that the LASI drawing will be centered in the LASI drawing area, and you can use the full LASI drawing area. Starting Conversion When you are happy with the setup, press ALT-G or click "Go" to start conversion. The main processes will be indicated as the program runs. A count of the TLC objects will be displayed and will be written to the report. It is a good idea to make a report for future reference. Note: The counts show the actual number of TLC object records. The (Vertex) count shows how many vertices will be needed when the TLC objects are changed to internal LASI object records. If you have previously run GDS2TLC, there will be a setup file in the drawing directory named GDS2TLC.SET. If this is found, the setup parameters will be loaded when you first run GDS2TLC, and will be stored again as you start the conversion. This saves a great deal of time when running GDS2TLC since you only have to modify any parameters. Scale Conversion As GDS2TLC converts each individual structure, it checks each dimension (4-byte signed integer) for the least resolution (or coarsest grid) that will fit that particular structure. As it converts structures, it determines the least resolution that will convert ALL structures correctly, and displays it as the Minimum Feature size in the Scale Bar at the bottom of the screen. The number of LASI units needed to convert ALL structures is the reciprocal of the Minimum Feature. If you don't need the resolution of the original GDS drawing, you can set the LASI units to less than the GDS units. An example of this is when the original GDS contains arcs that were made with a resolution of a single grid unit. Usually you can use a much coarser grid, since when made into photomasks, the resolution will be no better than the mask making equipment. If you get a "Resolution Lost" warning, the LASI Units that were set caused some original GDS coordinate position to be misplaced. The new coordinate will be rounded to the LASI grid. Read Errors and Warnings. Note: Path widths in a GDS file (WIDTH records) should be drawn to HALF the resolution of position coordinates (XY records). If they are not, you can have the situation where the path sides will be on half LASI basic unit positions. LASI will tolerate this, but the sides will be drawn on either higher or lower basic unit positions, or a path side will be tilted between different basic units at either end. If this happens you should double your LASI Units. Conversion Process To convert from Stream Format, GDS2TLC goes through several processes to determine the criterion it will use to convert. GDS2TLC first scans the GDS file several times to determine a hierarchy of cells. It also tries to convert structure names to names that are MS-DOS acceptable. If a name is found that is a reserved word such as "PRN", or the name contains characters that are illegal in MS-DOS such as "*", depending on the setup switch (above), you will be asked for a substitute name. You will be continuously asked until you give an acceptable name. GDS2TLC will search the current directory for the TLC cell file of a cell that might not exist as a structure in the GDS file, but still be used in other structures in the GDS file. This allows the TLC file of a cell to be reconstructed without the lesser cells being present as structures in the GDS file. The only requirement is that the TLC files of its lesser cells exist already in the drawing directory. After the scanning has been done to establish hierarchy and the presence of TLC files, a list of the cellnames, their rank, the presence of the structure in the GDS file, the presence of a TLC file in the directory and the structure name is printed. Different colors are used to indicate the presence of GDS and TLC. Red indicates that a cell is missing. As explained above, if a TLC file is already present, it is retained even though the structure may exist in the GDS file. To have a new TLC file generated, the old TLC file must be deleted from the current directory, or the option of replacing all TLC files must be used when running GDS2TLC. If a LESSER cell does not exist as a structure in the GDS file, and the lesser's TLC file does not exist in the destination directory, then the name of the expected cell is inserted as TEXT into the TLC file being made and a warning message is given. Errors and Warnings Most errors ar self-explaining. The warnings that GDS2TLC lists as it converts are as follows: "Open Poly at ..." means that the first and last points of a boundary converted to a polygon were not the same. Note: The X=,Y= reported is always the first point of a poly or path or the lower left corner of a box. L= is the layer. "Resolution Lost ..." means that the number of LASI Units per Phys Unit was incorrect for the GDS dimensions. The number of LASI units may have been too small, or the LASI grid may have been the wrong size to fit the GDS dimensions exactly. The number given is the minimum number of LASI basic units that are needed. LASI units that are an INTEGRAL multiple of the number will also be correct. "(Object) Limit Reached". A GDS structure converted to more boxes, paths, vertices or cells than LASI has been designed. If you exceed the poly or vertex limit, and if you have not already done it, try converting 4-sided boundaries to boxes instead of polygons. "Structure is Missing ... Token Cell Made". GDS2TLC was unable to find the definition of a structure used as an SREF in other structures. GDS2TLC made a TLC file of a cell consisting of the text: "<<name>>". "Stream (Record Length, Record Type, Data Type) is Wrong". Your GDS file has an error in its basic format - you need a new GDS file. "Fatal Error ... Unrecognized Record Type". The GDS file had a coding error or a record type that GDS2TLC didn't know about. Send the GDS file to the author if possible. "Fatal Error ... Data Type Error". A type of data was read that was not 0-6 as expected in the GDS format. File is probably corrupted. "String Data Length Exceeds Allocation". ASCII string data was found that was longer than 32 characters for names and 512 characters for general strings. The string was truncated. "Too Many Structures in GDS File". The internal limit of 1600 different structures in the GDS file was exceeded. Try breaking the GDS file into smaller files with fewer unrelated structures, if possible. Possible Problems Converting from Stream Format is a little tricky because there are data forms in GDS that are unique and hard to carry over into LASI. These are some of the known problems: 1. When converting from GDS to LASI, if any structures are missing and a TLC file is not present, there is no way to tell if the missing structures or TLC files contain other missing structures or cells. 2. Presently, arrays of objects do not exist in LASI. Therefore, when converting from GDS, GDS2TLC makes arrays by copying cells. This can fill the LASI cell capacity if you don't watch out. 3. When GDS2TLC encounters text in a GDS file, it ignores justification and breaks down any multi-line text into single line LASI text objects. This means that your translated text may not be located exactly in the same place. You should also use only single line left-justified text on the other drawing system if you intend to bring it into LASI. 4. Some features of GDS are presently simply ignored, such as stretched components, and nodes. 5. If you abort while GDS2TLC is making a TLC file you will probably get an incomplete file. Erase it. Parameter Line Editor Parameter Line Editor Both programs now use a simple line editor that resembles the editor used with Windows. The editor operates as follows: ■ To move from parameter to parameter, press the UP/DOWN ARROW keys, (SHIFT)TAB, or click the mouse on a parameter. ■ Press PGUP/PGDN to move to the first or last parameter. ■ Press LEFT/RIGHT ARROW to move the text cursor left or right. ■ Press HOME/END to move the cursor to the beginning or end of a line. ■ Press BACKSPACE to erase a character to the left of the cursor. ■ Press DELETE to erase the character to the right of the cursor. ■ Press CTRL-BACKSPACE to completely erase a text line. ■ When you first select a parameter, typing any printable character other than SPACE or LEFT/RIGHT ARROW will replace the whole text line. ■ Press ENTER to return to the main page. ■ If you make a mistake press ESC to restore the original text.