bus-not-modeled

Remedy ¶

Resolve the bus into its member nets, usually by labelling each member at its tap or by declaring the bus on its hierarchical port. Until then, connectivity over those signals is unmodelled and any diff or highlight across them is unreliable.

What it means ¶

A bus on the schematic (a gEDA U segment, a KiCad bus / bus_alias, an xschem NAME[n:0] label, or an EDIF array port) whose member signals are NOT all resolved into distinct nets. The bus names a set of members (a range DATA[7:0] expands to DATA0..DATA7, or a bus_alias lists them); the finding fires when one or more of those members is not a net in the read.

Why engineers want it ¶

A bus is a drawing shorthand: one line stands for many signals. What matters for every downstream answer (a diff, a rule, a highlight) is that each member ends up as its own net. On a flat sheet that already happens: KiCad requires a member label on every bus tap, so the members form nets by name and the bus is effectively modeled. The finding is SILENT there. It fires where the members are genuinely unresolved, so the read-gap is visible instead of silent.

Impact ¶

Corrupt or missing connectivity for the unresolved members, with no other symptom until a rule misfires or a diff lies. Info severity because the cause is the reader, not the design.

The one subtlety ¶

Resolution is checked by member NAME. A flat sheet’s member labels are bare (DATA0), so they match the bus’s expanded members and the bus reads as resolved. A hierarchy read qualifies a sheet-local member net per instance (/amp1/DATA0), which does NOT match the bare DATA0, correctly flagging a bus whose members do not cross a sheet boundary (a hierarchical bus port), the case where connectivity really is lost. Verified against kicad-cli sch export netlist: a flat bussed sheet produces exactly the member nets, so the rule stays silent on it.

Scope note ¶

Detection + resolution-checking is where this rule stops. Actually EXPANDING a bus across a sheet boundary (a hierarchical bus port) into crossing member nets is the remaining WS1-034 work; until then this rule flags those cases rather than silently mis-reading them. Drawing the bus trunk on the canvas is a separate concern (WS7-042).

Query structure ¶

report each bus whose members are not all present as nets.

select B in unmodeled_buses where exists M in members(B) : not net_exists(M)

Reads: bus.construct (a reader diagnostic), net.names. Tier P.