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rohanku
commented
Sep 25, 2026
rohanku
commented
Contributor
- fix(sky130): preserve MOS parameters that Substrate does not model
- fix(spectre): escape signal names in save and ic statements
`convert_spice_mos` built a `MosParams` from `w`, `l` and `nf * m * mult` and dropped every other parameter, so importing a SPICE netlist through the `Sky130` schema silently lost information: * Junction areas and perimeters (`ad`, `as`, `pd`, `ps`) were discarded. The SKY130 models default these to zero, so a round trip removed all source/drain junction capacitance. For the foundry SRAM bitcell this cut the capacitance a 64-row column presents to a bit line from 7.30 fF to 2.83 fF, making read timing optimistic by 60%. * Stress parameters (`sa`, `sb`, `sd`) and resistances (`nrd`, `nrs`) were discarded. * `m` and `mult` were folded into `nf`. The models treat all three differently -- `nf` is a finger count that divides the supplied width, `m` is an instance multiplier, and `mult` only appears in the mismatch-slope expressions -- so collapsing them changes the device. `Primitive::Mos` now carries an `extra` map of the parameters Substrate does not model, populated on import and merged back in on export. `nf` is taken from the `nf` parameter alone. Where a schema derives a key that can also appear in `extra` -- `mult` for SRC NDA, `m` and `mult` for CDS -- the two are multiplied, since both are device multipliers. MOSFETs that Substrate generates itself carry an empty `extra` and are unaffected. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
`save` and `ic` wrote the name of a `SimSignal::Raw` verbatim. Spectre only accepts `[`, `]` and `#` in an identifier when they are escaped, so saving a bus bit or a node imported from layout -- `din[0]`, or `...Xdff_6.a_1800_291#` -- made Spectre reject the netlist during circuit read-in rather than run. `Spectre::escape_path` escapes those characters while preserving what gives a path its meaning: `.` between hierarchy elements, `:` before a terminal, and the `*`/`?` wildcards that `save` accepts. It is applied through a new `SimSignal::to_netlist_string`, so only the two netlisting call sites change; result lookup still uses the unescaped name, which is what Spectre reports back. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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