While doing a parasitic exraction it is possible that there are more than one net short, the way to find this out is to check the transcript that is created bt the run_script file. use the command "run_script > transcript" to create the transcript. use "vi transcript" to view it, check if any short circuit information is present. If you find any short circuts listed, then use/add the following command line in your rules file " LVS ISOLATE SHORTS YES BY LAYER UNMERGED CELL ALL " After this do the extraction. Then you can do a LVS from the Calibre menu in IC to do a check. Compare the Layout to netlist, the layout is the GDS file and the netlist will be the one that was created by PEX. In LVS you can see a SHORTS Database. View it and highlight the shorts one after the other. Now you know where the short is, fix it and be happy. [Written by: Charles Thangaraj] [August 9th 2004] -------------Original full document follows -------------------- LVS Isolate Shorts Specification statement LVS ISOLATE SHORTS NO LVS ISOLATE SHORTS YES [BY LAYER] [UNMERGED] [{CELL PRIMARY | CELL ALL} [operand NAME text_name [... text_name]]] [FLAT] Summary Controls creation of an LVS short isolation database. Parameters * NO A secondary keyword that instructs LVS not to perform short isolation. This is the default behavior if you do not include this statement in your rule file * YES A secondary keyword that instructs LVS to perform short isolation. * BY LAYER An optional secondary keyword that specifies to generate output in separate DRC checks per short per layer. * UNMERGED An optional secondary keyword that instructs hierarchical LVS not to merge segmented polygons prior to output. Normally, hierarchical short isolations segments polygons for processing and then merges them before output. This keyword must appear before the NAME keyword if both are specified. This option is rarely used. * CELL PRIMARY | CELL ALL An optional secondary keyword set that specifies where hierarchical LVS isolates shorts between text objects. CELL PRIMARY - Isolates shorts between text objects in the primary cell. CELL ALL - Isolates shorts between text objects in all cells. In each cell, Calibre isolates shorts in that cell or its sub-hierarchy, that involve text objects local to that cell. This parameter is ignored in flat applications and cannot be specified with the FLAT parameter. * operand An optional replaceable string that indicates logical symbols that combine the CELL and NAME parameters. Possible choices are: && - Isolates a short if it satisfies both the CELL and NAME parameters: same as Boolean AND. || - Isolates a short if it satisfies either the CELL or NAME parameters: same as Boolean OR. * NAME text_name An optional secondary keyword, followed by one or more names, that instructs the tool to isolate shorts between the specified names. The text_name specifies a text object name, which can contain one or more question mark (?) characters. The ? is a wildcard character that matches zero or more characters. Specifying a single text_name parameter only makes sense if you use a wildcard. When you specify the NAME parameter, then CELL and operand parameters must precede the NAME parameter. The FLAT parameter cannot be specified. If you do not include the NAME parameter, the default behavior of this parameter is: && NAME "?" and results in the tool processing all text object names. Flat Calibre applications ignore the NAME parameter. * FLAT An optional secondary keyword that instructs the tool to perform the short isolation stage flat, even when executing hierarchical circuit extraction. When you specify the FLAT parameter, you cannot specify the CELL and NAME parameters. Description Shorts occur when there are conflicting text objects on the same net. This statement finds and outputs the shortest path between two conflicting text points. The default is NO. The statement can be specified once in your rule file. When short isolation is enabled, it is executed in flat LVS or layout-to-Cnet translation, both in Calibre and within ICtrace, and during hierarchical circuit extraction in Calibre (that is, calibre -spice). Any of these commands can be used to perform short isolation in Calibre: calibre -lvs rules calibre -lvs -tl lay.cnet rules calibre -spice lay.net rules calibre -spice lay.net -lvs -hier -hcell cells rules The first two commands perform flat short isolation. The last two commands perform short isolation hierarchically. Shorts are isolated in the layout. The Layout System must be GDSII, CIF, ASCII, or BINARY. Short isolation is not performed if the layout system is EDDM, SPICE, or Cnet. Processing is independent of Text Depth in all cells, except the top-level cell, where text objects selected from the Text Depth setting are treated as if they are at the top level. In Calibre, the short isolation results are written in DRC-ASCII database format to the file lvs_report_name.shorts if an LVS Report name was supplied, or lvs.layout_cell_name.rep.shorts otherwise. The layout_cell_name is the cell name specified by the Layout Primary specification statement. In ICgraph, layout_cell_name is the name of the top-level cell associated with the active IC Station window (regardless of the editing context). The result file can be viewed with any application that can read DRC-ASCII files, such as Calibre RVE or ICgraph. In ICgraph, the result file can be loaded and the shorts viewed using the ICrules buttons for restoring DRC databases and then viewing DRC checks. All short isolation results are returned in the coordinate space of the top level cell. In hierarchical operation, results from lower-level cells are shown only once. The lowest leftmost placement of a cell in the design is used as representative for shorts occurring in that cell. In the results database, each short appears as a separate DRC-style check having a name that is composed of the names of the nets that have been shorted together (for example, SHORT 5. vss - vdd - vcc or SHORT 2. IN1 - OUT2). When the BY LAYER keyword is not specified, one DRC check is generated per short and it includes all layers. The check names are then of the form: SHORT . - - ... - where is a serial identifier of the short, and are names of the shorted nets. For example: SHORT 5. vss - vdd - vcc. SHORT 2. IN1 - OUT2. In LVS-H, short isolation is enabled when the BY LAYER option is specified and performed whenever circuit extraction occurs. DRC check names in the short isolation results database contain the name of the cell where the short occurred. The DRC check name format is shown here. SHORT . - - ... - in () A result contains all shapes on that describe the given short. The is a layer name or layer number. Each short is a list of polygons that describe a shortest path connecting the text points in question. Distance is measured by number of (merged) polygons in the path (note that this is not necessarily always the geometrically shortest distance). Examples: SHORT 1. IN1 - OUT2 SHORT 1. VCC - VDD - VXX in cellx (MET1) Each check contains a check comment (called check text) with information about text objects involved in the particular short. For each text object, the text value, location and layer are indicated. For example: SHORT 1. VDD - VSS in AVMRAM (MT2) 1 1 3 Feb 2 11:16:59 2001 2 Shorted texts: "VDD" at (5642.3,520.1) on layer "MT2LG" "VSS" at (5651.1,519.95) on layer "MT2LG"