{"schemaVersion":1,"slug":"iec-d-latch","name":"IEC transparent D latch (rectangular form)","kind":"symbol","abbreviation":"C1 1D","aliases":["IEC level-sensitive latch","transparent latch IEC form","C1 1D latch"],"category":"logic-signals","drawingTypes":["Schematic"],"referenceFamilies":["IEC","Manufacturer"],"summary":"IEC bistable with a static C1 control and 1D input; the output follows D while C1 is active.","description":["The transparent latch is drawn like the D flip-flop but the C1 input has no dynamic wedge. While C1 is at its internal 1 state, the output follows the 1D input; when C1 returns to 0 the last value is held. TI's overview describes this as a level-operated control input.","Latches are used to capture data from a bus or to hold a value for a display or relay driver. In octal devices the common-control block carries C1 and the output enable, with eight per-bit elements below.","Because the output follows the input during the active level, glitches on D during that time pass through. The symbol shows this behaviour only through the absence of the wedge, so check it carefully."],"readingNotes":["No wedge on C1 means level-sensitive.","In octal parts, look for C1 in the common-control block."],"drawingChecklist":["Draw C1 without a dynamic mark.","Prefix the data input with 1.","Show output enable separately if present."],"distinction":"The IEC D flip-flop has a dynamic wedge on C1 and captures only at the edge.","facts":[{"label":"Clock type","value":"Level-operated"},{"label":"Key labels","value":"C1, 1D"},{"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":"Transparent latch behaviour with level-operated control input."},{"sourceId":"pub-electronics-ti-hc373","relevance":"Transparent latch documentation."}],"related":["transparent-d-latch","iec-d-flip-flop","iec-common-control-block"],"artwork":"s28-iec-d-latch","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","symbolVariant":{"convention":"IEC","form":"Rectangular bistable with static C1 and 1D inputs","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. The counterpart is the matching functional concept; no equivalence of every detailed standard graphic is asserted.","counterpart":"transparent-d-latch"},"plainEnglish":{"title":"What does IEC transparent D latch (rectangular form) mean?","introduction":"The transparent latch is drawn like the D flip-flop but the C1 input has no dynamic wedge. While C1 is at its internal 1 state, the output follows the 1D input; when C1 returns to 0 the last value is held. TI's overview describes this as a level-operated control input.","example":"Latches are used to capture data from a bus or to hold a value for a display or relay driver. In octal devices the common-control block carries C1 and the output enable, with eight per-bit elements below.","drawings":"Because the output follows the input during the active level, glitches on D during that time pass through. The symbol shows this behaviour only through the absence of the wedge, so check it carefully.","terms":[{"name":"Normally open / normally closed","meaning":"The contact state in the normal condition defined for the drawing."},{"name":"Coil","meaning":"A wound conductor that can produce a magnetic field when energised."},{"name":"Signal","meaning":"Electrical information passed between devices, rather than necessarily the main power supply."}],"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"},{"label":"SN74HC373 — transparent D latches","url":"https://www.ti.com/lit/ds/symlink/sn74hc373.pdf"}],"detail":"IEC bistable with a static C1 control and 1D input; the output follows D while C1 is active. The IEC D flip-flop has a dynamic wedge on C1 and captures only at the edge.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/iec-d-latch","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/iec-d-latch.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":"Transparent latch behaviour with level-operated control input."},{"id":"pub-electronics-ti-hc373","title":"SN74HC373 — transparent D latches","publisher":"Texas Instruments","url":"https://www.ti.com/lit/ds/symlink/sn74hc373.pdf","type":"manufacturer","scope":"Public device-function and terminal documentation used as an example of transparent d latches. Example part numbers are manufacturer identifiers, not IEC/IEEE symbol IDs. Device ratings, pin numbering and availability remain in the selected product documentation.","checkedOn":"2026-10-14","reuse":"link-only","relevance":"Transparent latch documentation."}]}