# IEC postponed output qualifier Canonical URL: https://eloragrid.ai/symbols/iec-postponed-output Publisher: Elora Grid Updated: 2026-10-28 Lookup label: POSTPONED Drawing use: Schematic Reference families: IEC, Manufacturer ## Symbol convention Convention: IEC Form: Angle mark inside the outline next to the output 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. Angle mark beside an output showing it changes only when the initiating input returns to its original level. ## In plain English ### What does IEC postponed output qualifier mean? The postponed output additional drawing mark is a small right-angle mark inside the outline next to an output. It indicates that the output changes when the input that initiated the change, typically the C input, returns to its initial external state. It identifies pulse-triggered or master-slave flip-flops and data lock-out types. ### A simple example This matters for timing analysis. On a pulse-triggered device the data must be stable for the whole time the clock is active, whereas on an edge-triggered device only setup and hold around the edge matter. The mark tells the reader which rule applies. ### What the drawings help you do The additional drawing mark does not distinguish a pulse-triggered element from a data lock-out element; the clock input marking does. A dynamic mark on C with a postponed output indicates the data lock-out form. ### This particular reference Angle mark beside an output showing it changes only when the initiating input returns to its original level. An edge-triggered flip-flop has a dynamic C input and no postponed output mark. ### Terms - Signal: Electrical information passed between devices, rather than necessarily the main power supply. - Schematic: A drawing showing function and connections rather than physical appearance. Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram. - [Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)](https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf) ## What it represents The postponed output qualifier is a small right-angle mark inside the outline next to an output. It indicates that the output changes when the input that initiated the change, typically the C input, returns to its initial external state. It identifies pulse-triggered or master-slave flip-flops and data lock-out types. This matters for timing analysis. On a pulse-triggered device the data must be stable for the whole time the clock is active, whereas on an edge-triggered device only setup and hold around the edge matter. The mark tells the reader which rule applies. The qualifier does not distinguish a pulse-triggered element from a data lock-out element; the clock input marking does. A dynamic mark on C with a postponed output indicates the data lock-out form. ## How to read it - Find the mark at each Q output of a flip-flop. - Check the C input for a dynamic mark to identify the data lock-out type. ## Information to show or reference - Draw the mark inside the outline at the output. - Show C input marking consistently. - Note data stability requirements for pulse-triggered devices. ## Important distinction An edge-triggered flip-flop has a dynamic C input and no postponed output mark. ## Facts - Meaning: Output changes when the initiating input returns - Typical device: Master-slave or pulse-triggered flip-flop - Artwork scope: Original educational illustration; consult the applicable standard and the selected device documentation for the exact graphic ## Public references - [Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)](https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf) — Texas Instruments. Defines the postponed output qualifier and pulse-triggered element behaviour. ## Graphic scope Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.