Profile contract
ladder.basic@1
IEC 61131-3 LD: power rails, rungs (one data block per rung, declaration order top to bottom), NO/NC contacts, output coils (normal/set/reset/negated) right-aligned at the rail, parallel OR branches inferred from series topology, fbd.block/fbd.variable hosted on rungs, labels/jumps/returns. Dedicated rung layout algorithm (layout.algorithm: ladder).
graph projectionIEC 61131-3 ladder diagram
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Primary palette
Relationship roles
Legal endpoints
| Relation | Source roles | Target roles | Self relation |
|---|---|---|---|
fbd.wire | fbd.block, fbd.variable | fbd.block, fbd.variable | Not allowed |
ladder.series | fbd.block, fbd.variable, ladder.coil, ladder.contact, ladder.jump, ladder.label, ladder.return | fbd.block, fbd.variable, ladder.coil, ladder.contact, ladder.jump, ladder.label, ladder.return | Not allowed |
Profile verification
- Each data block is one rung, in declaration order; exactly one output coil per rung.
- Series links stay in the same rung; parallel OR branches follow declared topology. Jump target is a selected label.
- Require ladder layout; render rails and right-aligned coil, contact/coil variants and hosted FBD pins.
Profile defaults
Explicit file settings override eligible CSS, then these profile defaults and the common standard apply. Unspecified semantic facts remain unspecified.
{
"projection.kind": "graph",
"projection.profile": "ladder.basic@1",
"layout.algorithm": "ladder",
"contact.form": "no",
"coil.mode": "normal"
}Projection properties
kind, profile, inputs, analysis_budget, traces, iso, depth
Design operations
- Create rung; add contact/coil/FBD/label/jump/return; connect series branches; edit contact form/coil mode/jump target.
Bounded analysis
Structural verification and display only; no execution or implied process engine.
Outside this profile
- PLC execution/compilation
- IEC interchange (XML) formats
- formal IEC certification