# IEC dynamic input with negation (falling edge)

Canonical URL: https://eloragrid.ai/symbols/iec-falling-edge-dynamic-input
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: DYN-NEG
Drawing use: Schematic
Reference families: IEC, Manufacturer

## Symbol convention

Convention: IEC
Form: Wedge inside the outline combined with an external negation circle or polarity triangle
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.

Clock wedge combined with a negation circle or polarity triangle, so the input acts on a falling edge.

## In plain English

### What does IEC dynamic input with negation (falling edge) mean?

Combining the dynamic input wedge with input negation, or with a polarity indicator, means the input is active on the transition from high to low. TI's public overview tabulates how the active transition reads in positive logic, negative logic and polarity notation.

### A simple example

Negative-edge clocking appears in JK flip-flops and some counters, and in designs where two stages are clocked on opposite edges. A reader must check both the wedge and the external mark before deciding which edge the device responds to.

### What the drawings help you do

The symbol does not state duty-cycle or minimum pulse width requirements; those come from device timing data. The input waveform must satisfy those limits at the active falling transition, not just reach a valid steady logic level.

### This particular reference

Clock wedge combined with a negation circle or polarity triangle, so the input acts on a falling edge. A wedge without an external mark is rising-edge triggered.

### 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)
- [SN74HC112 — negative-edge JK flip-flops](https://www.ti.com/lit/ds/symlink/sn74hc112.pdf)


## What it represents

Combining the dynamic input wedge with input negation, or with a polarity indicator, means the input is active on the transition from high to low. TI's public overview tabulates how the active transition reads in positive logic, negative logic and polarity notation.
Negative-edge clocking appears in JK flip-flops and some counters, and in designs where two stages are clocked on opposite edges. A reader must check both the wedge and the external mark before deciding which edge the device responds to.
The symbol does not state duty-cycle or minimum pulse width requirements; those come from device timing data. The input waveform must satisfy those limits at the active falling transition, not just reach a valid steady logic level.

## How to read it

- Look outside the outline for the circle or triangle as well as inside for the wedge.
- Opposite-edge clocking between stages is often deliberate.

## Information to show or reference

- Draw both the wedge and the external negation mark.
- Keep notation consistent with the rest of the sheet.
- Annotate the clock net with its active edge if mixed edges are used.

## Important distinction

A wedge without an external mark is rising-edge triggered.

## Facts

- Meaning: Active on high-to-low transition
- Typical device: Negative-edge JK 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. Tabulates dynamic input forms for each logic convention.
- [SN74HC112 — negative-edge JK flip-flops](https://www.ti.com/lit/ds/symlink/sn74hc112.pdf) — Texas Instruments. Negative-edge JK flip-flop documentation.

## 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.