{"schemaVersion":1,"slug":"iec-read-only-memory","name":"IEC read-only memory (ROM)","kind":"symbol","abbreviation":"ROM","aliases":["ROM element","IEC ROM symbol","read-only memory block"],"category":"logic-signals","drawingTypes":["Schematic"],"referenceFamilies":["IEC","Manufacturer"],"summary":"IEC element marked ROM with grouped address inputs and data outputs that read the addressed word.","description":["A ROM is drawn with the ROM qualifier, usually followed by its organisation such as 256x8. Address inputs are grouped with a binary grouping bracket marked A, and data outputs carry an A label to show they deliver the addressed word. Enable inputs often control three-state outputs.","On control drawings ROM symbols document lookup tables, character generators or firmware storage on logic boards. The organisation figure tells a reviewer the address range and data width at a glance.","The symbol does not show the stored content. The content reference, such as a firmware or table file revision, should be noted next to the symbol."],"readingNotes":["Organisation such as 256x8 gives words by width.","Data outputs carry the A label."],"drawingChecklist":["State the organisation.","Group address inputs with A notation.","Reference the content revision."],"distinction":"RAM adds write inputs; ROM outputs only.","facts":[{"label":"Qualifier","value":"ROM"},{"label":"Notation","value":"A dependency on data outputs"},{"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":"Lists ROM and describes A dependency for memories."}],"related":["iec-random-access-memory","iec-address-dependency-a","iec-fifo-memory"],"artwork":"s28-iec-read-only-memory","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","symbolVariant":{"convention":"IEC","form":"Rectangular element with ROM qualifier, address grouping and A-dependent outputs","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 read-only memory (ROM) mean?","introduction":"A ROM is drawn with the ROM additional drawing mark, usually followed by its organisation such as 256x8. Address inputs are grouped with a binary grouping bracket marked A, and data outputs carry an A label to show they deliver the addressed word. Enable inputs often control three-state outputs.","example":"On control drawings ROM symbols document lookup tables, character generators or firmware storage on logic boards. The organisation figure tells a reviewer the address range and data width at a glance.","drawings":"The symbol does not show the stored content. The content reference, such as a firmware or table file revision, should be noted next to the symbol.","terms":[{"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":"IEC element marked ROM with grouped address inputs and data outputs that read the addressed word. RAM adds write inputs; ROM outputs only.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/iec-read-only-memory","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/iec-read-only-memory.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":"Lists ROM and describes A dependency for memories."}]}