#

## ext, extract

Circuit netlist extractor

### Usage:

> extract option

> > where option may be one of the following:
> > all
> >   Extract the root cell and all its children. This bypasses the incremental extraction and ensures that a new `.ext` file is written for every cell definition.
> > cell name
> >   Extract the currently selected cell into file name
> > do|no [option]
> >   Enable or disable an extractor option, where option may be one of the following:

> >   > capacitance
> >   >   Extract local parasitic capacitance values to substrate
> >   > coupling
> >   >   Extract the parasitic coupling capacitance between nodes.
> >   > lumped
> >   >   Extract lumped resistance values. The values extracted are "lumped" resistance and indicate the value for which the delay through the net can be computed with R times C, where R is the lumped resistance and C is the parasitic capacitance. This is a very coarse approximation, as it assumes equal delay from the driver to any receiver. For full R-C extraction, see the extresist command. Lumped resistances have no meaning in SPICE netlists and will only be used when running ext2sim to generate a .sim netlist. Prior to magic version 8.3.597, this option was resistance, but as that was often confused with full parasitic resistance extraction, it has been changed.
> >   > length
> >   >   Extract the length of the shortest path from a driver to a receiver, for computing more accurate parasitic resistances.
> >   > adjust
> >   >   Adjust all capacitances for overlap between a parent cell and child instance, or between instances in an array. Parasitic capacitance is removed to account for the amount of overlap. Note that this method can produce negative capacitors in the parent. When the netlist is flattened for simulation, the total of all capacitances in parent and child, or between array instances, is guaranteed to be strictly positive.
> >   > all
> >   >   Apply all standard options (does not include options "local", "labelcheck", "aliases", or "resistance").
> >   > local
> >   >   Write all .ext files to the current working directory. If not specified, each .ext file will be placed in the same directory as the .mag file from which it is derived, unless the .mag file is in a directory which is not writable. In that case, the .ext file will also be written to the current working directory.

> >   >   Note: As of magic version 8.3.404, "extract do local" effectively implements "extract path ." and "extract no local" implements " extract path none".

> >   > labelcheck
> >   >   Check for labels which have zero area and connect to a subcell on the edge; this case is rare but is computationally expensive to check for, so the feature is disabled by default.
> >   > aliases
> >   >   By default (starting with version 8.3.217), magic only extracts a single name for a net, unless the net connects to a port, in which case the port name is extracted as well. With the aliases option enabled, all names for a net are extracted; this can be useful for debugging but will usually just slow down processing by commands like "ext2spice" that use the .ext file contents, so it is disabled by default.
> >   > unique [notopports]
> >   >   (Added in magic version 8.3.594) This setting replaces the use of the command option "extract unique" (and "extract unique notopports"). Instead of changing labels in the design, unique labels are generated for the duration of the extraction, and then reverted back to the original text. The "extract unique" command option is maintained for backwards compatibility. Note the difference: "extract unique" is a command that runs immediately, and cannot be undone; "extract do unique" is an option setting for "extract".
> >   > resistance
> >   >   (Added in magic version 8.3.597) This setting replaces the use of the standalone command "extresist". The effect is the same: Magic performs full R-C extraction, generating a `.res.ext` file that annotates the existing `.ext` file (see the "extresist" command documentation). The "extresist" command options can still be used to set options such as tolerance for the R-C extraction. Note that prior to magic version 8.3.597, this option name would produce the lumped resistance approximation (see lumped, above).

> >   These options (except for "local") determine how much information is written to the output file. By default, all options are selected. Normally, the options in ext2spice or ext2sim are used to select which information from the .ext file is used in the resulting netlist. There is no need to restrict the information being extracted. All options add relatively little overhead to the extraction time. The output file size can be reduced by not generating some extraction information.
> > length [option]
> >   Control pathlength extraction information, where option may be one of the following:

> >   > driver termname
> >   > receiver termname
> >   > clear

> > halo [distance]
> >   Return or set the maximum distance between shapes for which sidewall coupling is considered. distance is in the units of snap distance (lambda, by default), but like all distances may be specified with a suffix like "um" for physical distance. The default value is set by the technology file. Smaller values will decrease the parasitic capacitance extraction time at the expense of accuracy. When distance is not specified, the value returned is always in internal units.
> > help
> >   Print help information
> > path [pathname|none]
> >   Extract locally into the directory pathname. If pathname does not exist, then magic will attempt to create it. If it cannot be created, then the behavior will be to save extract files in the current working directory. If no path is set, or if none is specified as the path, then the behavior will be to extract files in the same directory as where the magic database (.mag) file is located, unless that directory is unwritable by the user, in which case the file is extracted to the current working diretory. Note that "extract do local" is the same as "extract path ." and "extract no local" is the same as "extract path none". Also note that netlist generation is independent of extraction, and needs to specify the same path as used by extract path, e.g., "ext2spice -p pathname".
> > parents
> >   Extract the selected cell and all its parents
> > showparents
> >   List the cell and all parents of selected cell. Note that this is not really an extract option and is superceded by the cellname command.
> > stepsize [distance]
> >   Return or set the step size used when breaking a layout into smaller parts for more efficient extraction. distance is in the units of snap distance (lambda, by default), but like all distances may be specified with a suffix like "um" for physical distance. The default value is set by the technology file. Both large and small values make extraction inefficient, and finding the optimal step size is largely trial-and-error. The step size in a tech file has most likely already been optimized for extraction speed. When distance is not specified, the value returned is always in internal units.
> > [list|listall] style [stylename]
> >   Set the current extraction style to stylename. Without arguments, print the current extraction style. With keyword list, return the current extraction style as a Tcl result. With keyword listall, return all valid extraction styles for the technology as a Tcl list.
> > unique [#]
> >   Generate unique names when different nodes have the same name. When option "#" is present, only make unique names for labels tagged by ending with the "#" character.
> >   Warning: This operation immediately modifies the existing layout in preparation for extraction. Label modifications are permanent, and cannot be undone. All cells in the hierarchy may potentially be modified.
> > unique [option]
> >   (From Magic 8.1.24) With no option, generate unique names when different nodes have the same name. option may be one of the following:

> >   > all
> >   >   Equivalent to no option; all labels with the same name on different nets are given unique names.
> >   > #
> >   >   Labels that are tagged by ending with the character "#" are made unique for each instance on an electrically unique node.
> >   > noports
> >   >   Labels that are not ports are made unique when on different nets. Ports, however, are ignored. This option is useful for standard cells which may be hiding internal connectivity.
> >   > notopports
> >   >   This option behaves like extract unique noports on the topmost cell in the hierarchy, and otherwise behaves like extract unique all on all cells below the top (available from magic 8.3.205).

> >   Warning: This operation immediately modifies the existing layout in preparation for extraction. Label modifications are permanent, and cannot be undone. All cells in the hierarchy may potentially be modified. To avoid this issue, use the "extract do unique" option instead (see above).
> > warn [[no] option]
> >   Enable/disable reporting of non-fatal errors, where option may be one of the following:

> >   > fets
> >   > labels
> >   > dup
> >   > all

### Summary:

> With no options given, the extract command incrementally extracts the root cell and all its children into separate `.ext` files. With options, the effect is as described in the Usage section above.

### Implementation Notes:

> extract is implemented as a built-in magic command.

> ext is an alias for command extract (allowed abbreviation where the usage would otherwise be ambiguous).

### See Also:

> extresist
> ext2spice
> ext2sim

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Last updated: October 8, 2021 at 4:56pm