net.max_voltage

What it is ¶

net.max_voltage(net, volts) yields one row per net that declares a rail voltage, pairing the net name with a number. It is emitted only where the design states a voltage. An explicit max_voltage attribute on the net wins, and otherwise the value is read from the net’s name (a rail named +5V, 3V3, or 12V0 names its own nominal). A net with neither channel produces no row, so the relation is a partial map over nets, not a value for every net.

For hardware engineers ¶

The netlist actually knows the working voltage of these supply rails. Most signal nets carry no voltage claim, so they are simply absent here. During a review you query it to see which rails the tool can reason about numerically, and to feed a comparison against a part’s ratings, such as a join against a datasheet absolute maximum. Suppose a rail you expected does not appear. Then the extractor could not read its name as a voltage, or the name holds two disagreeing tokens like 12V_TO_5V, and the extractor refuses to guess between them.

For software engineers ¶

It resolves a net to a declared constant, with a miss when nothing declares one. It is a projection over Nets() in which the extractor tries each net’s explicit attribute first, then the name, and skips the net when both fail. Rows are 1:1 with the nets that have a declared voltage; an empty result means no net in the design states or names a voltage. The value is carried as a number, so a query can range or compare on it without re-parsing the 5V text form.

Go projector ¶

netMaxVoltageFacts in stdlib/relations/facts.go walks Model.Nets() and, for each net, calls check.RailMaxVoltage(n, n.Name) (in core/check/params.go). That helper returns the explicit max_voltage attribute when present, else the name-derived nominal (nominalVoltageFromName), and reports ok=false when neither yields a number. The projector emits a row only when ok is true, filling both the rendered 5V-style value and the numeric field. One row per net that declares a voltage; empty when no net declares or names one.

Datalog ¶

List every net with a declared voltage:

net.max_voltage(?n, ?v) => ?n, ?v

Find the rails above 3 V and the parts sitting on them:

net.max_voltage(?n, ?v), ?v > 3, component.net(?r, ?n) => ?r, ?n, ?v