netgen

Comparing netlists (LVS)

netgen checks that two netlists describe the same circuit: usually a layout's extracted netlist (Magic's ext2spice lvs) against the schematic it should implement. It matches devices and nets by how they connect, not by their names, then reports what differs: nets, devices, pins, and device sizes (properties).

In the Compare window, choose the two netlists, the cell in each (the subcircuit; .sim and .ext files hold one cell), and a setup file, then Run LVS. The Result window shows the verdict, the nets and devices that differ, side by side, property differences and pins, and netgen's full report.

Setup files

A setup file (Tcl) tells netgen which device names are the same, which terminals can swap, and which properties to compare. Process kits ship one (for sky130, sky130A_setup.tcl): add it to the project and choose it. The built-in scmos setup suits Magic's scmos technology. Without one, netgen uses defaults.

Commands

The console runs any netgen or Tcl command. A few:

lvs {a.spice cell} {b.spice cell} setup.tcl out.txt -json: What Run LVS does
readnet file · cells list 0: Read a netlist; list its cells
writenet spice {a.spice cell}: Write a cell in another format
reinitialize: Forget all netlists
help: All netgen commands

Mixing case-sensitive formats (.sim, .ext, Verilog) with SPICE: netgen keeps the case sensitivity of the file it reads first, so put the SPICE netlist first when node names differ only in case. Stop ends a command that runs too long: netgen starts again and replays the commands before it.

Projects

Project > Open files or Open folder copies netlists and setup files, or one .zip / .tar.gz, into the page; you can also drop them on it. To keep your work, work in a folder on disk (Chrome, Edge and other Chromium browsers) or keep the project in browser storage (any browser): reports netgen writes and your edits in the Files window are saved there.

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