open-source-silicon.dev

Is there a way in xschem to mark some components as bypassed or non existent for LVS ?
Like I'd like to include some caps that are only simulating the parasitics during sim but shouldn't be on the LVS netlist. Or including `ampmeter` that also abviously be replaced by short during LVS.

Ah wait ... there is `lvs_ignore` I missed that the first time I looked, that seems to be exactly what I need ...

correct, `lvs_ignore=true` or `lvs_ignore=1` set on the instance (or symbol if you want to apply everywhere it is used) will ignore the component.
`lvs_ignore=short` will transform the component into a short so all component pins will be the same electrical net.

`lvs_ignore` attributes are considered if global option "`LVS->set lvs_ignore variable`" is enabled.

1.png

The circuit on the left is for spice simulation. Enabling global  "`LVS->set lvs_ignore variable`" (or via cli: `set lvs_ignore 1`) will transform to the circuit on the right where the ammeter (`lvs_ignore=short` attribute) no more exists (it is propagating the `A` net name) and capacitor is removed (`lvs_ignore=1` attribute).
Shorted elements are painted in red, ignored ones are painted in dashed grey.

<@U06413JAUEN> Shift-t toggles the `spice_ignore` attribute, not the `lvs_ignore`.
spice_ignore and lvs_ignore do essentially the same thing, enable / disable / short component instances, but lvs_ignore setting is enabled by global flag lvs_netlist (`Simulation-&gt;LVS-&gt;set lvs_netlist variable`). So you can toggle this global and all instances with lvs_ignore set are disabled / shorted.

I think devices that are useful for simulation but to be removed in LVS should have their `lvs_ignore` attrinute set. This attribute has no effect until you "enable it" with the above mentioned `lvs_netlist` global setting.