# IEC decade counter (CTR DIV10)

Canonical URL: https://eloragrid.ai/symbols/iec-decade-counter
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: CTR DIV10
Drawing use: Schematic
Reference families: IEC, Manufacturer

## Symbol convention

Convention: IEC
Form: Rectangular element with the CTR DIVm qualifier, m = 10
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.

IEC counter marked CTR DIV10, counting through ten states with BCD-weighted outputs.

## In plain English

### What does IEC decade counter (CTR DIV10) mean?

CTR DIVm identifies a counter whose cycle length is m. A decade counter is therefore CTR DIV10, with outputs weighted 1, 2, 4 and 8 for a BCD count from 0 to 9. The carry output is often marked CT=9 to show it is active at the last state.

### A simple example

Decade counters drive numeric displays through BCD-to-seven-segment decoders and form decimal dividers in timing circuits. A drafter cascading stages should show the CT=9 carry feeding the enable of the next decade.

### What the drawings help you do

This differs from a decoded one-of-ten counter, which provides ten separate outputs rather than a BCD code. Check the outputs before assuming either form.

### This particular reference

IEC counter marked CTR DIV10, counting through ten states with BCD-weighted outputs. The decoded decade counter has ten one-hot outputs rather than BCD-weighted outputs.

### 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

CTR DIVm identifies a counter whose cycle length is m. A decade counter is therefore CTR DIV10, with outputs weighted 1, 2, 4 and 8 for a BCD count from 0 to 9. The carry output is often marked CT=9 to show it is active at the last state.
Decade counters drive numeric displays through BCD-to-seven-segment decoders and form decimal dividers in timing circuits. A drafter cascading stages should show the CT=9 carry feeding the enable of the next decade.
This differs from a decoded one-of-ten counter, which provides ten separate outputs rather than a BCD code. Check the outputs before assuming either form.

## How to read it

- DIV10 states a cycle of ten.
- CT=9 marks the carry used to cascade decades.

## Information to show or reference

- Use CTR DIV10 rather than CTR4 for BCD counters.
- Show BCD output weights.
- Show cascading between decades.

## Important distinction

The decoded decade counter has ten one-hot outputs rather than BCD-weighted outputs.

## Facts

- Qualifier: CTR DIV10
- Outputs: BCD weights 1, 2, 4, 8
- 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 CTR DIVm and contents outputs such as CT=9.

## 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.