{"schemaVersion":1,"slug":"iec-mode-dependency-m","name":"IEC mode dependency (M)","kind":"symbol","abbreviation":"Mm","aliases":["M dependency","mode select dependency","Mm mode input"],"category":"logic-signals","drawingTypes":["Schematic"],"referenceFamilies":["IEC","Manufacturer"],"summary":"Dependency label Mm used to show operating modes; affected inputs and outputs act only in the selected mode.","description":["M dependency is used where a device has several operating modes. When an Mm input is at its internal 1 state, inputs and outputs labelled m have their normal effect; otherwise they are disabled. Mode inputs are often produced from two select lines by binary grouping, giving M0 to M3.","Universal shift registers and up/down counters are typical users. On the symbol, a label such as 1,4D means the input acts as data only in mode 1 and with control 4. Reading these compound labels from left to right gives the order of conditions.","The notation does not define what happens during a mode change. Any restrictions on changing mode while clocking are device-specific."],"readingNotes":["Decode the mode inputs before reading other labels.","Compound labels list affecting numbers separated by commas."],"drawingChecklist":["Show the mode-select inputs and their binary grouping.","Label affected terminals with the mode numbers.","Tabulate the modes in a note if the symbol is complex."],"distinction":"A (address) dependency selects among arrays of identical elements; M selects operating modes of one element.","facts":[{"label":"Affecting input at 1","value":"Permits action (mode selected)"},{"label":"Typical device","value":"Universal shift register"},{"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":"M (mode) dependency affecting inputs and outputs."}],"related":["iec-bidirectional-shift-register","iec-up-down-counter","iec-address-dependency-a"],"artwork":"s28-iec-mode-dependency-m","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","symbolVariant":{"convention":"IEC","form":"Mode inputs labelled Mm, often produced by binary grouping, with affected terminals 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 mode dependency (M) mean?","introduction":"M dependency is used where a device has several operating modes. When an Mm input is at its internal 1 state, inputs and outputs labelled m have their normal effect; otherwise they are disabled. Mode inputs are often produced from two select lines by binary grouping, giving M0 to M3.","example":"Universal shift registers and up/down counters are typical users. On the symbol, a label such as 1,4D means the input acts as data only in mode 1 and with control 4. Reading these compound labels from left to right gives the order of conditions.","drawings":"The notation does not define what happens during a mode change. Any restrictions on changing mode while clocking are device-specific.","terms":[{"name":"Signal","meaning":"Electrical information passed between devices, rather than necessarily the main power supply."},{"name":"Rating","meaning":"A value stating the conditions for which equipment is specified."},{"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 label Mm used to show operating modes; affected inputs and outputs act only in the selected mode. A (address) dependency selects among arrays of identical elements; M selects operating modes of one element.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/iec-mode-dependency-m","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/iec-mode-dependency-m.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":"M (mode) dependency affecting inputs and outputs."}]}