mirror of
https://github.com/RTimothyEdwards/magic.git
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R. Timothy Edwards
718e02ec3f
after much discussion about the implementation. Since it is not exactly clear what the field lines do at corners, the implementation depends largely on an unknown and presumably global constant multiplier; this has provisionally been set to 1 but needs to be determined empirically with a field equation solver. At least one rational approximation suggests a value of pi/2 instead of 1. The corner capacitance can be considered a refinement of existing parasitic capacitance extraction, and since it takes a non-trivial additional amount of computation, it is left as an option to "extract" that can be turned on when a more accurate result is preferred at the expense of a longer extraction time.
315 lines
13 KiB
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315 lines
13 KiB
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<TITLE>Magic-8.3 Command Reference</TITLE>
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<BODY BACKGROUND=graphics/blpaper.gif>
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<H1> <IMG SRC=graphics/magic_title8_3.png ALT="Magic VLSI Layout Tool Version 8.3">
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<IMG SRC=graphics/magic_OGL_sm.gif ALIGN="top" ALT="*"> </H1>
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<H2>ext, extract</H2>
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<HR>
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Circuit netlist extractor
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<HR>
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<H3>Usage:</H3>
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<BLOCKQUOTE>
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<B>extract</B> <I>option</I> <BR><BR>
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<BLOCKQUOTE>
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where <I>option</I> may be one of the following:
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<DL>
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<DT> <B>all</B>
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<DD> Extract the root cell and all its children. This bypasses
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the incremental extraction and ensures that a new <TT>.ext</TT>
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file is written for every cell definition.
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<DT> <B>cell</B> <I>name</I>
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<DD> Extract the currently selected cell into file <I>name</I>
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<DT> <B>do</B>|<B>no</B> [<I>option</I>]
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<DD> Enable or disable an extractor option, where <I>option</I>
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may be one of the following:
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<BLOCKQUOTE>
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<DL>
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<DT> <B>capacitance</B>
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<DD> Extract local parasitic capacitance values to substrate
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<DT> <B>coupling</B>
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<DD> Extract the parasitic coupling capacitance between
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nodes.
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<DT> <B>corners</B> [<I>value</I>]
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<DD> (Added in magic version 8.3.672) Extract the fringe
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capacitance at the corners of shapes. The fringe
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capacitance model measures capacitance outward from
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shape edges, which does not account for the part of
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the fringe field at a convex corner that couples to
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shapes diagonal to the corner, or for the
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double-counting of the fringe field from the two
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edges meeting at a concave corner. With this option
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enabled, the corner fringe capacitance is modeled as
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a superposition of the fields of the two edges
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meeting at each corner, and is added to (convex) or
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subtracted from (concave) both the substrate
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capacitance and the coupling capacitance.
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The optional <I>value</I> (default 1.0) is a
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dimensionless scale factor on the corner capacitance
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model. This is a second-order correction which
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increases extraction time, so it is disabled by
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default, and is not included in the options enabled
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by "<B>all</B>".
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<DT> <B>lumped</B>
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<DD> Extract lumped resistance values.
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The values extracted are "lumped" resistance and
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indicate the value for which the delay through the
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net can be computed with R times C, where R is the
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lumped resistance and C is the parasitic capacitance.
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This is a very coarse approximation, as it assumes
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equal delay from the driver to any receiver. For
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full R-C extraction, see the <B>extresist</B>
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command. Lumped resistances have no meaning in
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SPICE netlists and will only be used when running
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<B>ext2sim</B> to generate a .sim netlist.
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Prior to magic version 8.3.597, this option was
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<B>resistance</B>, but as that was often confused
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with full parasitic resistance extraction, it has
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been changed.
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<DT> <B>length</B>
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<DD> Extract the length of the shortest path from a driver
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to a receiver, for computing more accurate parasitic
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resistances.
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<DT> <B>adjust</B>
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<DD> Adjust all capacitances for overlap between a parent
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cell and child instance, or between instances in an
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array. Parasitic capacitance is removed to account
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for the amount of overlap. Note that this method
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can produce negative capacitors in the parent. When
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the netlist is flattened for simulation, the total
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of all capacitances in parent and child, or between
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array instances, is guaranteed to be strictly positive.
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<DT> <B>all</B>
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<DD> Apply all standard options (does not include options
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"local", "labelcheck", "aliases", or "resistance").
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<DT> <B>local</B>
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<DD> Write all .ext files to the current working directory.
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If not specified, each .ext file will be placed in the
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same directory as the .mag file from which it is
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derived, unless the .mag file is in a directory which
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is not writable. In that case, the .ext file will also
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be written to the current working directory. <P>
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<I>Note:</I> As of magic version 8.3.404, "<B>extract
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do local</B>" effectively implements "<B>extract path .</B>"
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and "<B>extract no local</B>" implements "<B> extract
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path none</B>".
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<DT> <B>labelcheck</B>
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<DD> Check for labels which have zero area and connect
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to a subcell on the edge; this case is rare but is
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computationally expensive to check for, so the feature
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is disabled by default.
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<DT> <B>aliases</B>
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<DD> By default (starting with version 8.3.217), magic only
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extracts a single name for a net, unless the net connects
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to a port, in which case the port name is extracted as
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well. With the <B>aliases</B> option enabled, all names
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for a net are extracted; this can be useful for debugging
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but will usually just slow down processing by commands
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like "ext2spice" that use the .ext file contents, so it
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is disabled by default.
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<DT> <B>unique</B> [<B>notopports</B>]
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<DD> (Added in magic version 8.3.594) This setting replaces
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the use of the command option "extract unique" (and
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"extract unique notopports"). Instead of changing labels
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in the design, unique labels are generated for the duration
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of the extraction, and then reverted back to the original
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text. The "extract unique" command option is maintained
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for backwards compatibility. Note the difference:
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"extract unique" is a command that runs immediately, and
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cannot be undone; "extract do unique" is an option setting
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for "extract".
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<DT> <B>resistance</B>
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<DD> (Added in magic version 8.3.597) This setting replaces
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the use of the standalone command "extresist". The
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effect is the same: Magic performs full R-C extraction,
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generating a <TT>.res.ext</TT> file that annotates the
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existing <TT>.ext</TT> file (see the "extresist" command
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documentation). The "extresist" command options can
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still be used to set options such as tolerance for the
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R-C extraction.
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Note that prior to magic version 8.3.597, this option
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name would produce the lumped resistance approximation
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(see <B>lumped</B>, above).
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</DL>
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</BLOCKQUOTE>
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These options (except for "local") determine how much
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information is written to the output file. By default,
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all options are selected. Normally, the options in
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<B>ext2spice</B> or <B>ext2sim</B> are used to select
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which information from the .ext file is used in the
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resulting netlist. There is no need to restrict the
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information being extracted. All options add relatively
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little overhead to the extraction time. The output file
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size can be reduced by not generating some extraction
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information.
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<DT> <B>length</B> [<I>option</I>]
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<DD> Control pathlength extraction information, where <I>option</I>
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may be one of the following:
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<BLOCKQUOTE>
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<DL>
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<DT> <B>driver</B> <I>termname</I>
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<DD>
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<DT> <B>receiver</B> <I>termname</I>
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<DD>
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<DT> <B>clear</B>
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<DD>
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</DL>
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</BLOCKQUOTE>
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<DT> <B>halo</B> [<I>distance</I>]
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<DD> Return or set the maximum distance between shapes for which
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sidewall coupling is considered. <I>distance</I> is in
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the units of snap distance (lambda, by default), but like
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all distances may be specified with a suffix like "um" for
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physical distance. The default value is set by the technology
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file. Smaller values will decrease the parasitic capacitance
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extraction time at the expense of accuracy. When <I>distance</I>
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is not specified, the value returned is always in internal
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units.
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<DT> <B>help</B>
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<DD> Print help information
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<DT> <B>path</B> [<I>pathname</I>|<B>none</B>]
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<DD> Extract locally into the directory <I>pathname</I>. If
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<I>pathname</I> does not exist, then magic will attempt to
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create it. If it cannot be created, then the behavior will
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be to save extract files in the current working directory.
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If no path is set, or if <B>none</B> is specified as the
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path, then the behavior will be to extract files in the
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same directory as where the magic database (<B>.mag</B>)
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file is located, unless that directory is unwritable by
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the user, in which case the file is extracted to the
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current working diretory. Note that "<B>extract do local</B>"
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is the same as "<B>extract path .</B>" and "<B>extract no local</B>"
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is the same as "<B>extract path none</B>". Also note that
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netlist generation is independent of extraction, and needs to
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specify the same path as used by <B>extract path</B>, e.g.,
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"<B>ext2spice -p</B> <I>pathname</I>".
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<DT> <B>parents</B>
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<DD> Extract the selected cell and all its parents
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<DT> <B>showparents</B>
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<DD> List the cell and all parents of selected cell. Note that
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this is not really an extract option and is superceded by
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the <B>cellname</B> command.
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<DT> <B>stepsize</B> [<I>distance</I>]
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<DD> Return or set the step size used when breaking a layout into
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smaller parts for more efficient extraction. <I>distance</I>
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is in the units of snap distance (lambda, by default), but like
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all distances may be specified with a suffix like "um" for
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physical distance. The default value is set by the technology
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file. Both large and small values make extraction inefficient,
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and finding the optimal step size is largely trial-and-error.
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The step size in a tech file has most likely already been
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optimized for extraction speed. When <I>distance</I> is not
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specified, the value returned is always in internal units.
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<DT> [<B>list</B>|<B>listall</B>] <B>style</B> [<I>stylename</I>]
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<DD> Set the current extraction style to <I>stylename</I>.
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Without arguments, print the current extraction style.
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With keyword <B>list</B>, return the current extraction
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style as a Tcl result. With keyword <B>listall</B>, return
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all valid extraction styles for the technology as a Tcl
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list.
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<DT> <B>unique</B> [<I>#</I>]
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<DD> Generate unique names when different nodes have the same name.
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When option "<I>#</I>" is present, only make unique names for
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labels tagged by ending with the "<B>#</B>" character. <BR>
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<I>Warning:</I> This operation immediately modifies the
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existing layout in preparation for extraction. Label
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modifications are permanent, and cannot be undone. All
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cells in the hierarchy may potentially be modified. <BR>
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<DT> <B>unique</B> [<I>option</I>]
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<DD> (From Magic 8.1.24) With no option, generate unique names
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when different nodes have the same name. <I>option</I> may
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be one of the following:
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<BLOCKQUOTE>
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<DL>
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<DT> <B>all</B>
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<DD> Equivalent to no option; all labels with the same
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name on different nets are given unique names.
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<DT> <B>#</B>
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<DD> Labels that are tagged by ending with the character
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"<B>#</B>" are made unique for each instance on an
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electrically unique node.
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<DT> <B>noports</B>
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<DD> Labels that are not ports are made unique when on
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different nets. Ports, however, are ignored. This
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option is useful for standard cells which may be
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hiding internal connectivity.
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<DT> <B>notopports</B>
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<DD> This option behaves like <B>extract unique noports</B>
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on the topmost cell in the hierarchy, and otherwise
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behaves like <B>extract unique all</B> on all cells
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below the top (available from magic 8.3.205).
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</DL>
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</BLOCKQUOTE>
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<I>Warning:</I> This operation immediately modifies the
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existing layout in preparation for extraction. Label
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modifications are permanent, and cannot be undone. All
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cells in the hierarchy may potentially be modified. To avoid
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this issue, use the "extract do unique" option instead (see
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above). <BR>
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<DT> <B>warn</B> [[<B>no</B>] <I>option</I>]
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<DD> Enable/disable reporting of non-fatal errors, where <I>option</I>
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may be one of the following:
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<BLOCKQUOTE>
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<DL>
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<DT> <B>fets</B>
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<DD>
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<DT> <B>labels</B>
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<DD>
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<DT> <B>dup</B>
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<DD>
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<DT> <B>all</B>
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<DD>
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</DL>
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</BLOCKQUOTE>
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</DL>
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</BLOCKQUOTE>
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</BLOCKQUOTE>
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<H3>Summary:</H3>
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<BLOCKQUOTE>
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With no options given, the <B>extract</B> command incrementally
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extracts the root cell and all its children into separate
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<TT>.ext</TT> files. With options, the effect is as described
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in the Usage section above.
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</BLOCKQUOTE>
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<H3>Implementation Notes:</H3>
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<BLOCKQUOTE>
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<B>extract</B> is implemented as a built-in <B>magic</B> command. <P>
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<B>ext</B> is an alias for command <B>extract</B> (allowed
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abbreviation where the usage would otherwise be ambiguous).
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</BLOCKQUOTE>
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<H3>See Also:</H3>
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<BLOCKQUOTE>
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<A HREF=extresist.html><B>extresist</B></A> <BR>
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<A HREF=ext2spice.html><B>ext2spice</B></A> <BR>
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<A HREF=ext2sim.html><B>ext2sim</B></A> <BR>
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</BLOCKQUOTE>
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<P><IMG SRC=graphics/line1.gif><P>
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<TABLE BORDER=0>
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<TR>
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<TD> <A HREF=commands.html>Return to command index</A>
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</TR>
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</TABLE>
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<P><I>Last updated:</I> October 8, 2021 at 4:56pm <P>
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