{"schemaVersion":1,"slug":"iec-set-reset-dependency","name":"IEC set and reset dependency (S, R)","kind":"symbol","abbreviation":"Sm/Rm","aliases":["S dependency","R dependency","set-reset dependency notation"],"category":"logic-signals","drawingTypes":["Schematic"],"referenceFamilies":["IEC","Manufacturer"],"summary":"Dependency labels Sm and Rm: the affected output behaves as if set or reset when the affecting input is active.","description":["S and R dependencies specify the internal state of an output when both set and reset conditions could be active together. An Rm input at its internal 1 state makes the affected output react as it would to S=0, R=1; an Sm input does the opposite. At 0 they have no effect.","These labels are used where a storage element must have a defined priority between set and reset. A reader can see from the symbol whether set or reset dominates, which matters in latching alarm and interlock logic.","Plain S and R labels without numbers are the ordinary set and reset inputs of a bistable element. The dependency form only applies when a number follows the letter."],"readingNotes":["S or R followed by a number is a dependency; without a number it is an ordinary input.","Check which one dominates when both are active."],"drawingChecklist":["Number dependency inputs explicitly.","Label affected outputs with the matching number.","State set or reset priority in the logic description."],"distinction":"An ordinary R input resets the element directly; Rm dependency states the reaction of particular outputs.","facts":[{"label":"Rm at 1","value":"Output reacts as to S=0, R=1"},{"label":"Sm at 1","value":"Output reacts as to S=1, R=0"},{"label":"Artwork scope","value":"Original educational illustration; consult the applicable standard and the selected device documentation for the exact graphic"}],"references":[{"sourceId":"s28-ti-ieee91-logic-symbols","relevance":"S (set) and R (reset) dependencies and the summary table."}],"related":["iec-sr-latch","set-reset-latch","iec-clocked-sr-flip-flop"],"artwork":"s28-iec-set-reset-dependency","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","symbolVariant":{"convention":"IEC","form":"Affecting inputs labelled Sm or Rm with affected outputs labelled m","reference":"Qualifying-symbol and dependency conventions as explained in TI's public overview of IEEE Std 91-1984, which incorporates IEC 617-12 work. Independent educational drawing; not certified IEC geometry or an IEC database identifier."},"plainEnglish":{"title":"What does IEC set and reset dependency (S, R) mean?","introduction":"S and R dependencies specify the internal state of an output when both set and reset conditions could be active together. An Rm input at its internal 1 state makes the affected output react as it would to S=0, R=1; an Sm input does the opposite. At 0 they have no effect.","example":"These labels are used where a storage element must have a defined priority between set and reset. A reader can see from the symbol whether set or reset dominates, which matters in latching alarm and interlock logic.","drawings":"Plain S and R labels without numbers are the ordinary set and reset inputs of a bistable element. The dependency form only applies when a number follows the letter.","terms":[{"name":"Normally open / normally closed","meaning":"The contact state in the normal condition defined for the drawing."},{"name":"Signal","meaning":"Electrical information passed between devices, rather than necessarily the main power supply."},{"name":"Schematic","meaning":"A drawing showing function and connections rather than physical appearance."}],"diagram":"flow","steps":["Identify the device and form","Read the connections and state","Check the equipment reference"],"caption":"A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.","sources":[{"label":"Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)","url":"https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf"}],"detail":"Dependency labels Sm and Rm: the affected output behaves as if set or reset when the affecting input is active. An ordinary R input resets the element directly; Rm dependency states the reaction of particular outputs.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/iec-set-reset-dependency","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/iec-set-reset-dependency.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"s28-ti-ieee91-logic-symbols","title":"Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)","publisher":"Texas Instruments","url":"https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf","type":"manufacturer","scope":"Public explanation of rectangular logic symbols, general qualifiers, input and output qualifiers, dependency notation, bistable elements and coders, consistent with IEC 617-12 work.","checkedOn":"2026-10-28","reuse":"link-only","relevance":"S (set) and R (reset) dependencies and the summary table."}]}