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CIF

Caltech Intermediate form (CIF) is a low level graphics langage for specifying the geometry of integrated circuits. In contrast with GDS, the CIF is a text format exposed by nature to a different user interpretation and expansion. It appears that even the root format definitions are not quite followed by some of the major EDA vendors. Toped CIF interfaces are written to comply with CIF 2.0 definition as described in "A Guide to LSI implementation, Second Edition" by Robert W. Hon and Carlo H.Sequin. Toped is using also some of the CIF user expansions for which although "widely accepted" an authorithative reference was not found. See the wiki pages for more details on Toped CIF interface implementation.

[Note]Note

CIF interface might be updated in the future releases in case of compatibility problems with the major EDA vendors. Please do report incompatibilities.

CIF Layer Maps
The layer maps are presented in a form of lmap lists. They can be saved in a TELL variable and reused for import/export. The idea is that the user can interface with different technologies without redefining its toped layers. Each member of the CIF layer map is in the format described below. The format allows several CIF layers to merged into a single TDT layer.
[Tip]{tdt_lay, "cif_layer"}
int tdt_lay
This is the key field of the lmap structure which contains the TDT layer number. That TDT layer will be the target layer for import operations and source layer during the export.
string cif_layer
This string contains the CIF layer name according to the CIF 2.0 format description.

cifread

Parse a CIF file - this is the first step of the two-step process of CIF conversion. When executed this function parses the CIF file into memory checking it for validity, hierarchy structure and used layers. The function returns a list of strings containing the names of the top-level structures in the parsed file. To convert a CIF structure into TDT, use cifimport. When done, call cifclose to free the memory occupied by this operation. Only one CIF DB can reside in memory at a time. cifread will automatically remove the previous CIF database (if any) from the memory.

[Tip]string list cifread(file_name)
string file_name
A valid file name - platform dependent. OS environmental variables may be used.Compressed files are accepted as well - zip and gz formats.

Example 1. cifread

   string list top_s = cifread("/home/guest_user/layout/delivery.cif");

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cifimport

Convert CIF structure to TDT cell - this is the second step of the CIF import process. Function requires that a CIF file has been already parsed into the memory using cifread. It transfers the data from CIF representation into the corresponding TDT types. It is important to note that this function does not create a new TDT database. Instead it simply adds new cells to the TDT. This is supposed to facilitate the work of transferring layout blocks from design to design.

[Tip]cifimport …

void cifimport (top_structures, layer_map, recursive, overwrite)

void cifimport (top_structure, layer_map ,recursive, overwrite)

string list top_structures
A list of names of the top CIF structures to be imported.
string list top_structure
The name of the top CIF structure to be imported.
lmap list layer_map
The layer map to be used during the conversion.
bool recursive
Defines recursive behavior of the function. If true, the function will convert all the structures referenced directly or indirectly by the top structures. If false only the top structure will be converted.
bool overwrite
Defines the overwrite policy. If true - the cells created by the conversion will overwrite the TDT cell with the same name (if they exists). If false, the existing TDT cells will be preserved - i.e. CIF cell will not be converted if a TDT cell with this name already exists.

Toped will import only the layers listed in the layer_map. The layers not listed there will be silently omited. The function getciflaymap can be used to obtain the defualt layer map of the parsed CIF database.

Example 2. cifimport

   cifimport("top", {{1,"L01"}, {3,"L03"}, {4,"POLY"}}, true, false);
   cifimport(cifread("test_file.cif"), defaultciflaymap(), true, false);

In the example above, current TDT layout database will be updated with the CIF hierarchy starting with the cell named top_structure. All existing TDT cells will be preserved. Only 3 layers form the CIF data base will be imported.

The second example will convert the entire test_file.cif using default CIF layer map

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cifclose

Clean-up the memory from the CIF data parsed with cifread. After executing cifclose, cifimport can not be called until the next cifread. It is important to use this function, when parsed CIF database is no longer required.

[Tip]void cifclose ()
-

Example 3. cifclose

   cifclose();

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cifexport

Convert TDT database to CIF - The function translates the active layout or part of it database into CIF format.

[Tip]cifexport …

void cifexport (layer_map, filename_name, verbose_slang)

void cifexport (cell_name, recursive, layer_map, filename_name, verbose_slang)

string cell_name
The name of the top TDT cell to be exported.
bool recursive
Defines recursive behavior of the function. If true, the function will convert all the structures referenced directly or indirectly by the top structure. If false only the top structure will be converted.
lmap list layer_map
The layer map to be used during the conversion.
string file_name
A valid file name - platform dependent. OS environmental variables may be used.
bool cif_slang
By definition CIF syntax is failry free and allows a wide variety of "slangs". Toped maintains two type of CIF output which should be equivalent. The verbose dialect might not accepted by all tools. The default value of this option should be false

Toped will export only the layers listed in the layer_map. The layers not listed there will be silently omited. The function getciflaymap can be used to obtain the defualt layer map of the TDT data base.

Example 4. cifexport

   cifexport({{2,"L2"}, {4,"L4"}}, "/home/user/layout/seed.cif", false);
   cifexport("crop" , true, getciflaymap(false), "seed_part.cif", false);

In the first example above, current TDT layout database will be exported, but only layers 2 and 4. In the second one, cell hierarchy starting with the cell named crop will be converted, including all referenced cells.

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report_ciflayers

Prints the list of used layers in a CIF structure. The function can be used only if there is a CIF database in the memory.

[Tip]layout report_ciflayers( struct_name )
string struct_name
Target structure name

This function always takes into account the layers used in the entire hierarchy of structures, starting from struct_name.

Example 5. report_ciflayers

   report_ciflayers("some_struct");

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getciflaymap

Returns TDT-CIF layer map suitable for use in the interface functions cifimport and cifexport. The function checks whether a layer map has been already saved in the memory (see setciflaymap). It returns the saved map if it exists. If a map doesn’t exists in memory - the function generates a default layer map.

[Tip]lmap list getciflaymap( import )
bool import
Import and export functions might have different requirements for the layer map esspecially when Toped generates the default layer map. This parameter brings the information about the purpose of the generated map. It must be set to true if the generated map is going to be used in cifimport and false if it will be used in cifexport

If a default layer map can not be generated the function will issue an error on the log window. Depending on the input parameter this could be because a TDT ot CIF data base doesn’t exists in the memory.

Example 6. getciflaymap

   lmap list cifExportMap = getciflaymap(false);
   cifexport(cifExportMap, "all_design.cif", false);

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setciflaymap

Stores a TDT-CIF layer map as a Toped property. The map can be later retrieved using getciflaymap and is also used as an initial layer map in the CIF import/export dialogue boxes. The map will be dumped along with other editor properties by propsave

[Tip]void setciflaymap( layer_map )
lmap list layer_map
The layer map to be saved as a Toped property.

Example 7. setciflaymap

   lmap list cifDefaultMap = {{2,"ACTI"},{4,"POLY"},{60,"TEXT"}};
   setciflaymap(cifDefaultMap);

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clearciflaymap

Clean-up the memory from the layer map stored by setciflaymap. After executing clearciflaymap, getciflaymap will return the default layer map.

[Tip]void clearciflaymap ()
-

Example 8. clearciflaymap

   clearciflaymap();

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