Ring counters (Johnson Ring Counter)

Ring counters (Johnson Ring Counter)
Ring counters (Johnson Ring Counter)

Ring counters, sometimes known as Johnson counters, are shift registers having two feedback stages, at least one of which is a flip-flop. The ring counter cycles between states using clock pulses before returning to the initial state. The Johnson counter has twice as many states and complemented feedback as the ring counter. The frequency divider mode is where these counters shine. Controlling and counting are the major uses of the ring counter. Some use them to manage car and bike flashing. This application modulates signals and switches without output delay. Ring counters detect which counter pin fails when attached to the circuit. Memory units are checked using them. Ring counters can be used as sequential circuits to store binary zero to fifteen numbers. Ring counter registers are used in computers for reduced transistors since they are simpler. Companies predefine the count, making it easier for users to use and debug.

Did you ever wonder how digital electronics work? Ring counters may be unfamiliar to beginners in logic circuits and sequential logic devices. However, understanding their basics helps unveil the inner workings of various kinds of technologies. Ring counters and how their simple but brilliant design allows them to count in circles will be explained in a few minutes. The simplicity of these complex-sounding components will surprise you. Stay with us to learn how to enjoy even frightening counter circuits! This beginner’s guide to ring counters will enhance your confidence whether you’re new to circuits or looking to learn more.


Ring Counters are integer counters in digital logic named after the “ring” they generate and count. These are circular counters. Ring Counters use cascaded flip-flops with the output of the last flip-flop coupled to the input of the first. A ring counter’s main feature is that not all outputs are high at once, except when reset. To reduce output reading time, the shift register’s flip-flop count is limited.


Virtual Channel Identifier is a key use of ring counters in telecommunications. Consider the ATM cell header structure to understand. The cell header is 5 bytes. The header has 23 bits for the Virtual Channel Identifier and 8 for the VirtualPath Identifier. include two 4-Bit HEC fields for error detection. The VCI of this ATM cell lets us choose a telecommunication channel path. ATM and other switching methods use Ring Counter Technology to ease network switching. Large cities usually have many subscribers.

Each subscriber may have a wide network of switches before connecting to the central public exchange, like a Manual Telephone Exchange. Each switch may require the consumer to call the relevant number before the number. Ring Counters help with this. Each subscriber can easily receive a Virtual Channel and set up a route to the public exchange using the Dial tone. A 4-bit ring counter may define 16 routes. We can link subscribers sequentially in many circumstances, from last to next.


Johnson counters, constructed by adding an inverter to every other flip-flop, turn twice as rapidly as ordinary ring or circular counters. Because Johnson counters are shorter than binary counters, their maximum count repetition time is their bit count. In addition to its advantages, the Johnson ring counter is speedier and fool-proof.

What Is a Ring Counter?

A ring counter circuit counts electrical pulses. Ring-connected flip-flops form a circular shift register. Each pulse shifts a bit around the ring.

  • Ring counters have these components:
  • Flip-flops store one bit of data. They are ring-connected.
  • A repeating clock signal changes each flip-flop state. Flip-flop bits shift with each clock pulse.
  • Switches all flip-flops to their initial condition. Starts the counter from zero.

Ring counters help:

Creating timing. Outputs can time and control other circuits.
Decoding the counter’s output to move a mechanical actuator or stepper motor.
A fixed-pattern repeating binary count sequence. Continuous counting will occur.
Ring counters have no maximum count value, which is its principal advantage over binary counters. It will count forever if clock pulses are applied. But the count sequence is set and repeating. Ring counters are cheap and effective for timing and control applications that require a repeating count sequence.

If this confused you, don’t worry! Initial understanding of ring counters is difficult. Flip flops and clock signals are the foundation. Ring counter applications and benefits become clearer when you grasp how each pulse shifts bits around the ring. With practice, you’ll design ring counters quickly!

How Does a Johnson Ring Counter Work?

The Johnson ring counter is a sequential logic device that changes states when pulsed. It has rings of flip-flops. Each flip-flop has two states: normal and complement.

Ring counter operation is simple. The first flip-flop changes state on input pulses. Flip-flop 2 switches state on the second pulse. Pulses are repeated until the last flip-flop changes state. The initial flip-flop changes state again on the next pulse, repeating the sequence.

To illustrate, a 3-bit ring counter would cycle between the states 000, 001, 010, 011, 100, 101, 110, 111, and 000. The counter cycles through 8 states before repeating.

Important ring counter facts:

Use them to generate time sequences, cyclic redundancy tests, and frequency dividers.
Number of flip-flops influences sequence length. More flip-flops lengthen cycles.
For an n-bit counter, they repeat after maximal 2n states.
The outputs can drive circuits to generate timing pulses or frequency divisions.
Short cycle lengths limit their usefulness, but they are easy to build.
To sum up, the Johnson ring counter is a simple sequential circuit with fixed states. Signal production, frequency division, and redundancy checks use repeating pulse sequences. Short cycles from a few flip-flops limit its usefulness, but it’s easy to make.

Ring Counter Applications and Uses

Ring counters are excellent for counting pulses and events. Commonly used in:

Digital clocks

Each condition of the ring counter keeps time and advances the display. Each state represents a display digit or segment.

Dividing a clock signal

To lower the frequency of its output signal, a ring counter can divide an input clock signal by its flip-flops. The 4-bit ring counter can split a signal by 16.

Generating pulse waveforms

Ring counters output pulse waveforms based on state count. A 3-bit ring counter generates an 8-clock-pulse waveform.

Controlling stepper motors

Pulses are controlled by the outputs to rotate a stepper motor. A ring counter ensures motor coils are ignited in order.

Managing the states of a finite state machine

The outputs represent state machine states. The ring counter cycles states based on inputs.Ring counters are a simple but useful way to generate several output signals in a repeating sequence for many digital applications. They control timing and coordinate events in circuits and systems despite their simplicity.

Designing and Implementing a Ring Counter Circuit

Design and build your own ring counter after learning how it works. Use J-K flip flops to build a simple ring counter circuit.Determine how many states you want your ring counter to have first. This example uses 4 J-K flip flops to create a 4-state ring counter. Connect one flip flop’s output to the next’s clock input. This causes a state-cycle chain reaction.

For clock edge toggling, the flip flops’ J and K inputs are linked to logic 1. This is the circuit diagram:

J=1, K=1 –> FF2 –> FF3 –> FF4 FF1

The ring is complete when the inverted output of the last flip flop is connected to the clock input of the first. The circuit will cycle through the 4 states using this feedback loop.

Finally, toggle the first flip flop’s clock input to logic 1 to start the series. The ring counter works by moving logic 1 along the chain of flip-flops with each clock pulse!

Additional ring counter circuit tips:

• Watch output state changes using a slow clock. About 1Hz works.

• Use LEDs to show status sequences. Connect one LED per flip-flop output.

• To reset, add a NAND gate to the feedback path. High RESET stops the sequence at the current state.

• Add flip flops for a higher state ring counter. Add more flip-flops to the chain!

Craft a ring counter circuit with inexpensive components to witness this vital counter in operation. Have more questions? Let me know!


Here are the basics of ring counters. We explained their structure, how they change states, and their main uses. Hope you now understand these ingenious tiny circuits. If these shift registers interest you, get a breadboard some chips and experiment! Seeing a Johnson counter march through its states will solidify your understanding faster than anything else. Who knows, you might find a new use for one. Electronics await! Start counting outside.

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