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## extresist

Patch the extraction `.ext` files with detailed route resistance information.

### Usage:

> extresist option

> > where option may be one of the following:
> > tolerance value
> >   Set the ratio between resistor and transistor tolerance for determining when to insert resistance into a network route.
> > all
> >   Extract all the nets.
> > simplify [on|off]
> >   Turn on/off simplification of resistor nets.
> > extout [on|off]
> >   Turn on/off writing of the `.res.ext` file.
> > lumped [on|off]
> >   Turn on/off writing of updated lumped resistances.
> > silent [on|off]
> >   Turn off/on printing of net statistics.
> > skip mask
> >   Don't extract types indicated in the comma-separated list mask
> > ignore [netname|none]
> >   Don't extract the net named netname. The list of ignored nets is global, cumulative, and persistent; it will only be cleared when the extresist ignore none command is issued (option available from version 8.3.207).
> > include [netname|all]
> >   Extract the net named netname. When this option is called at least once, the behavior of the extraction changes to extract only the nets that have been specified by extresist include commands. The list of included nets is global, cumulative, and persistent; it will only be cleared when the extresist include all command is issued (option available from version 8.3.213).
> > box type
> >   Extract the signal under the cursor box on layer type
> > cell cellname
> >   Extract the network for the cell named cellname
> > geometry
> >   Extract network geometry and present as a collection of line elements on the layout.
> > fasthenry [freq]
> >   Extract subcircuit network geometry into a fasthenry-format `.fh` file. If freq is specified, the file will be customized for fasthenry analysis at the indicated frequency (in Hz).
> > help
> >   Print help information

### Summary:

> The normal flow through layout extraction into a simulation file treats routes as nonphysical entities, that is, with infinitesimal impedence through the wires. Extraction for digital simulation using irsim generates "lumped resistances", a single resistance per network node that, along with the node capacitance to substrate, provides an RC time constant to approximately model the delay from point to point in the network node. The lumped resistance model is inappropriate for analog (i.e., SPICE) simulation, and for digital simulation, is a poor approximation for branching networks, where the delay between endpoints is different for each pair of endpoints in the network node.

> The extresist command provides a method for generating a more detailed model of resistance, in which long network routes and branching routes are replaced with resistor devices and device networks.

> Using extresist is a multi-step process. It is first necessary to run both extract and ext2sim to get the initial netlist (with lumped, not detailed, resistances). After a `.sim` file has been generated, the extresist all command may be run. The output is a file `.res.ext` for each cell in the hierarchy. Finally, with the option extresist on set, ext2sim or ext2spice will generate the final, detailed simulation file.

> More details on using extresist can be found in magic Tutorial number 8.

### Implementation Notes:

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

### See Also:

> extract
> ext2sim

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Last updated: October 4, 2021 at 3:32pm