n-bit Johnson Counter in Digital Logic Last Updated : 23 Aug, 2024 Comments Improve Suggest changes Like Article Like Report Prerequisite - Counters Johnson counter also known as creeping counter, is an example of synchronous counter. In Johnson counter, the complemented output of last flip flop is connected to input of first flip flop and to implement n-bit Johnson counter we require n flip-flop. It is one of the most important type of shift register counter. It is formed by the feedback of the output to its own input. Johnson counter is a ring with an inversion. Another name of Johnson counter are creeping counter, twisted ring counter, walking counter, mobile counter and switch tail counter. What is Johnson Counter?A Johnson counter is a type of a synchronous counter with a special counting pattern in this case being Johnson counter. It operates by the complemented output of the last flip flop feed back into the input of the first flip flop. What results from this setup is a series of states which forms a sequence that is not characteristic of normal ring counters.The Johnson counter can be implemented using n flip flops to count 2n distinct states – a feature that makes it better than a ring counter that uses an equal number of flip flops, as it serves twice the number of states. This counter is used in applications where the number of states is higher than the number of flip-flops; besides, it has a distinguishing feature of self-decodability.Total number of used and unused states in n-bit Johnson counter: number of used states=2n number of unused states=2n - 2*n Example: If n=4 4-bit Johnson counter Initially, suppose all flip-flops are reset. Truth Tablewhere, CP is clock pulse and Q1, Q2, Q3, Q4 are the states. Question: Determine the total number of used and unused states in 4-bit Johnson counter. Answer: Total number of used states= 2*n = 2*4 = 8 Total number of unused states= 2n - 2*n = 24-2*4 = 8 Difference Between Ring Counter and Johnson CounterParametersRing CounterJohnson CounterConfiguration A ring counter employs the carry-in of the last flip-flop into the input of the first flip-flop without any manipulation.In Johnson counter, the complement of output of the last flip-flop is applied to the input of the first flip-flop.Number of Flip- Flops'n' flip-flops are required to count 'n' states.'n' flip-flops are required to count '2n' states.Counting SequenceIt counts in a simple binary sequence often having one '1' and the rest '0's in each state.It counts in a twisted sequence, where the output is a mixture of binary 1s and 0s.Number of StatesIt can Generate 'n' unique statesIt can Generate '2n' unique states Unused statesNone, because all the states are utilized'2n-2n' states are unusedSelf-Decoding CapabilityIts not self-decoding since additional circuitry is neededIts self-decoding makes it simpler for certain applicationsCircuit ComplexitySince it does not require inversion feedback, thus the circuit is simple Due to inversion, the circuit is slightly more complexAdvantages of Johnson counterThe Johnson counter has same number of flip flop but it can count twice the number of states the ring counter can count.It can be implemented using D and JK flip flop.Johnson ring counter is used to count the data in a continuous loop.Johnson counter is a self-decoding circuit.Disadvantages of Johnson counterJohnson counter doesn't count in a binary sequence.In Johnson counter more number of states remain unutilized than the number of states being utilized.The number of flip flops needed is one half the number of timing signals.It can be constructed for any number of timing sequence.Applications of Johnson counterJohnson counter is used as a synchronous decade counter or divider circuit.It is used in hardware logic design to create complicated Finite states machine. ex: ASIC and FPGA design.The 3 stage Johnson counter is used as a 3 phase square wave generator which produces 1200 phase shift.It is used to divide the frequency of the clock signal by varying their feedback.ConclusionThis article has covered a number of aspects of Johnson counters ranging from how the system operates to the benefits of using the technology as well as shortcomings of the Johnson counters. Johnson counters are a subtype of shift register counter and they are capable of counting twice more states than a ring counter with similar flip flops. It can be seen that the fundamental differences between the ring counters and Johnson counters have been discussed above which can be used in selecting the proper counter circuits for certain digital circuit applications. Comment More infoAdvertise with us Next Article Number System and Base Conversions A azkia anam Follow Improve Article Tags : Misc GATE CS Digital Logic Practice Tags : Misc Similar Reads Digital Electronics and Logic Design Tutorials Digital Electronics and Logic Design are key concepts in both electronics and computer science. Digital systems are at the core of everything from basic devices like calculators to advanced computing systems. Digital systems use binary numbers (0s and 1s) to represent and process information.Logic g 4 min read Number SystemsNumber System and Base ConversionsElectronic and digital systems use various number systems such as Decimal, Binary, Hexadecimal and Octal, which are essential in computing. Binary (base-2) is the foundation of digital systems.Hexadecimal (base-16) and Octal (base-8) are commonly used to simplify the representation of binary data. T 9 min read 1's and 2's complement of a Binary NumberGiven a binary number s represented as a string. The task is to return its 1's complement and 2's complement in form of an array as [onesComplement, twosComplement].The 1's complement of a binary number is obtained by flipping all its bits. 0 becomes 1, and 1 becomes 0. Positive numbers remain uncha 8 min read BCD or Binary Coded DecimalBinary Coded Decimal (BCD) is a binary encoding system in which each decimal digit is represented by a fixed number of binary bits, typically four. Instead of converting the entire decimal number into a binary number, BCD represents each decimal digit separately as its binary equivalent. BCD powers 6 min read Error Detection Codes: Parity Bit MethodError Detection Codes: The binary information is transferred from one location to another location through some communication medium. The external noise can change bits from 1 to 0 or 0 to 1. This change in values changes the meaning of the actual message and is called an error. For efficient data t 6 min read Boolean Algebra and Logic GatesLogic Gates - Definition, Types, UsesLogic Gates are the fundamental building blocks in digital electronics. There are basically seven main types of logic gates that are used to perform various logical operations in digital systems. By combining different logic gates, complex operations are performed, and circuits like flip-flops, coun 10 min read Basic Conversion of Logic GatesIn the Digital System, logic gates are the basic building blocks.  In these logic gates, we can find the gates having more than one input, but will have only one output. The connection between the input and the output of a gate is based on some logic. Based on this logic, different gates are develop 6 min read Realization of Logic Gate Using Universal gatesIn Boolean Algebra, the NAND and NOR gates are called universal gates because any digital circuit can be implemented by using any one of these two i.e. any logic gate can be created using NAND or NOR gates only.Implementation of AND Gate using Universal GatesImplementation using NAND GatesThe AND ga 6 min read Canonical and Standard FormCanonical Form - In Boolean algebra, the Boolean function can be expressed as Canonical Disjunctive Normal Form known as minterm and some are expressed as Canonical Conjunctive Normal Form known as maxterm. In Minterm, we look for the functions where the output results in "1" while in Maxterm we loo 6 min read Types of Integrated CircuitsIn this article, we will go through the Types of Integrated Circuits, we will start our article with the introductions of the ICs, then we will go through different types of ICs one by one, At last, we will conclude our article will their applications, advantages, disadvantages and some FAQs. Table 7 min read Minimization TechniquesMinimization of Boolean FunctionsBoolean functions are used to represent logical expressions in terms of sum of minterms or product of maxterms. Number of these literals (minterms or maxterms) increases as the complexity of the digital circuit increases. This can lead to large and inefficient circuits. By minimizing Boolean functio 4 min read Introduction of K-Map (Karnaugh Map)In many digital circuits and practical problems, we need to find expressions with minimum variables. We can minimize Boolean expressions of 3, 4 variables very easily using K-map without using any Boolean algebra theorems. It is a tool which is used in digital logic to simplify boolean expression. I 5 min read 5 variable K-Map in Digital LogicPrerequisite - Implicant in K-Map Karnaugh Map or K-Map is an alternative way to write a truth table and is used for the simplification of Boolean Expressions. So far we are familiar with 3 variable K-Map & 4 variable K-Map. Now, let us discuss the 5-variable K-Map in detail. Any Boolean Express 5 min read Various Implicants in K-MapAn implicant can be defined as a product/minterm term in Sum of Products (SOP) or sum/maxterm term in Product of Sums (POS) of a Boolean function. For example, consider a Boolean function, F = AB + ABC + BC. Implicants are AB, ABC, and BC. There are various implicant in K-Map listed below :Prime Imp 5 min read Don't Care (X) Conditions in K-MapsOne of the most important concepts in simplifying output expressions using Karnaugh Maps (K-Maps) is the 'Don't Care' condition. The 'Don't Care' conditions allow us to treat certain cells in a K-Map as either 0, 1, or to ignore them altogether, which can help in forming larger and more efficient gr 4 min read Quine McCluskey MethodThe Quine McCluskey method also called the tabulation method is a very useful and convenient method for simplification of the Boolean functions for a large number of variables (greater than 4). This method is useful over K-map when the number of variables is larger for which K-map formation is diffi 8 min read Two Level Implementation of Logic GatesThe term "two-level logic" refers to a logic design that uses no more than two logic gates between input and output. This does not mean that the entire design will only have two logic gates, but it does mean that the single path from input to output will only have two logic gates.In two-level logic, 9 min read Combinational CircuitsHalf Adder in Digital LogicA half adder is a combinational logic circuit that performs binary addition of two single-bit inputs, A and B, producing two outputs: SUM and CARRY. The SUM output which is the least significant bit (LSB) is obtained using an XOR gate while the CARRY output which is the most significant bit (MSB) is 3 min read Full Adder in Digital LogicFull Adder is a combinational circuit that adds three inputs and produces two outputs. The first two inputs are A and B and the third input is an input carry as C-IN. The output carry is designated as C-OUT and the normal output is designated as S which is SUM. The C-OUT is also known as the majorit 5 min read Half Subtractor in Digital LogicA half subtractor is a digital logic circuit that performs the binary subtraction of two single-bit binary numbers. It has two inputs, A and B, and two outputs, Difference and Borrow. The Difference output represents the result of subtracting B from A, while the Borrow output indicates whether a bor 4 min read Full Subtractor in Digital LogicA Full Subtractor is a combinational circuit used to perform binary subtraction. It has three inputs:A (Minuend)B (Subtrahend)B-IN (Borrow-in from the previous stage)It produces two outputs:Difference (D): The result of the subtraction.Borrow-out (B-OUT): Indicates if a borrow is needed for the next 3 min read Parallel Adder and Parallel SubtractorAn adder adds two binary numbers one bit at a time using carry from each step. A subtractor subtracts one binary number from another using borrow when needed. A parallel adder adds all bits at once, making addition faster. Similarly, a parallel subtractor subtracts all bits at the same time for quic 5 min read Sequential Binary MultiplierIn this article, we are going to learn how a sequential binary multiplier works with examples. So for that, we also need to learn a few concepts related to the sequential circuit, binary multipliers, etc. Finally solving the examples using a sequential binary multiplier method.Sequential CircuitA se 12 min read Multiplexers in Digital LogicIn this article we will go through the multiplexer, we will first define what is a multiplexer then we will go through its types which are 2x1 and 4x1, then we will go through the Implementation of the 2x1 mux and higher mux with lower order mux, at last we will conclude our article with some applic 10 min read Event Demultiplexer in Node.jsNode.js is designed to handle multiple tasks efficiently using asynchronous, non-blocking I/O operations. But how does it manage multiple operations without slowing down or blocking execution? The answer lies in the Event Demultiplexer.The Event Demultiplexer is a key component of Node.js's event-dr 3 min read Binary Decoder in Digital LogicA binary decoder is a digital circuit used to convert binary-coded inputs into a unique set of outputs. It does the opposite of what an encoder does. A decoder takes a binary value (such as 0010) and activates exactly one output line corresponding to that value while all other output lines remain in 5 min read Encoder in Digital LogicAn encoder is a digital circuit that converts a set of binary inputs into a unique binary code. The binary code represents the position of the input and is used to identify the specific input that is active. Encoders are commonly used in digital systems to convert a parallel set of inputs into a ser 7 min read Code Converters - Binary to/from Gray CodeIn this article, we will go through Code Converters - Binary to/from Gray Code, we will start our article by defining Code converters, Binary code and Gray code, and then we will go through the conversion of binary code to gray code and vice versa.Table Of ContentCode ConvertersBinary CodeGray CodeC 5 min read Magnitude Comparator in Digital LogicA magnitude digital Comparator is a combinational circuit that compares two digital or binary numbers in order to find out whether one binary number is equal, less than, or greater than the other binary number. We logically design a circuit for which we will have two inputs one for A and the other f 7 min read Sequential CircuitsIntroduction of Sequential CircuitsSequential circuits are digital circuits that store and use the previous state information to determine their next state. Unlike combinational circuits, which only depend on the current input values to produce outputs, sequential circuits depend on both the current inputs and the previous state stor 7 min read Difference between Combinational and Sequential CircuitIn digital electronics, circuits are classified into two primary categories: The combinational circuits and the sequential circuits. Where the outputs depend on the current inputs are called combination circuit, combinational circuits are simple and effective for functions like addition, subtraction 4 min read Latches in Digital LogicLatch is a digital circuit which converts its output according to its inputs instantly. To implement latches, we use different logic gates. In this article, we will see the definition of latches, latch types like SR, gated SR, D, gated D, JK and T with its truth table and diagrams and advantages and 7 min read Flip-Flop types, their Conversion and ApplicationsIn this article, we will go through the Flip-Flop types, their Conversion and their Applications, First, we will go through the definition of the flip-flop with its types in brief, and then we will go through the conversion of the flip-flop with its applications, At last, we will conclude our articl 7 min read Conversion of Flip-FlopConversion of S-R Flip-Flop into D Flip-FlopPrerequisite - Flip-flop1. S-R Flip-Flop : S-R flip-flop is similar to S-R latch expect clock signal and two AND gates. The circuit responds to the positive edge of clock pulse to the inputs S and R. 2. D Flip-Flop : D Flip-Flop is a modified SR flip-flop which has an additional inverter. It prevent 1 min read Conversion of S-R Flip-Flop into T Flip-FlopPrerequisite - Flip-flop Here, we will discuss the process of conversion of S-R Flip-Flop into a T Flip-Flop using an example. Rules for conversion: Step-1: Find the characteristics table of required flip-flop and the excitation table of the existing (given) flip-flop. Step-2: Find the expression of 1 min read Conversion of J-K Flip-Flop into T Flip-FlopPrerequisite - Flip-flop 1. J-K Flip-Flop: JK flip-flop shares the initials of Jack Kilby, who won a Nobel prize for his fabrication of the world's first integrated circuit, some people speculate that this type of flip flop was named after him because a flip-flop was the first device that Kilby buil 1 min read Conversion of J-K Flip-Flop into D Flip-FlopA flip-flop is a basic component of digital electronics. This kind of circuit has two stable states and is frequently used in storing one bit of information. Various flip-flops such as SR (Set-Reset), D (Data or Delay), JK and T belong to this category. Each category has distinct features and functi 4 min read Register, Counter, and Memory UnitCounters in Digital LogicA Counter is a device which stores (and sometimes displays) the number of times a particular event or process has occurred, often in relationship to a clock signal. Counters are used in digital electronics for counting purpose, they can count specific event happening in the circuit. For example, in 4 min read Ripple Counter in Digital LogicCounters play a crucial role in digital logic circuits, enabling tasks such as clock frequency division and sequencing. This article explores the concept of ripple counters, a type of asynchronous counter, their operation, advantages, and disadvantages in digital logic design. What is a Counter?Coun 5 min read Ring Counter in Digital LogicA ring counter is a typical application of the Shift register. The ring counter is almost the same as the shift counter. The only change is that the output of the last flip-flop is connected to the input of the first flip-flop in the case of the ring counter but in the case of the shift register it 7 min read General Purpose RegistersA register is a collection of flip-flops. Single bit digital data is stored using flip-flops. By combining many flip-flops, the storage capacity can be extended to accommodate a huge number of bits. We must utilize an n-bit register with n flip flops if we wish to store an n-bit word.General Purpose 8 min read Shift Registers in Digital LogicPre-Requisite: Flip-FlopsFlip flops can be used to store a single bit of binary data (1 or 0). However, in order to store multiple bits of data, we need multiple flip-flops. N flip flops are to be connected in order to store n bits of data. A Register is a device that is used to store such informati 8 min read Computer MemoryMemory is the electronic storage space where a computer keeps the instructions and data it needs to access quickly. It's the place where information is stored for immediate use. Memory is an important component of a computer, as without it, the system wouldn’t operate correctly. The computer’s opera 9 min read Random Access Memory (RAM)Random Access Memory (RAM) is a type of computer memory that stores data temporarily. When you turn off your computer, the data in RAM disappears, unlike the data on your hard drive, which stays saved. RAM helps your computer run programs and process information faster. This is similar to how the br 11 min read Read Only Memory (ROM)Memory plays a crucial role in how devices operate, and one of the most important types is Read-Only Memory (ROM). Unlike RAM (Random Access Memory), which loses its data when the power is turned off, ROM is designed to store essential information permanently.Here, we’ll explore what ROM is, how it 8 min read LMNs and GATE PYQsLMN - Digital ElectronicsDigital electronics deals with systems that use digital signals, represented as 0s and 1s, to process information. It is the backbone of modern devices like computers, smartphones, and calculators. Unlike analog electronics, which works with continuous signals, digital electronics offers higher accu 14 min read Digital Logic and Design - GATE CSE Previous Year QuestionsThe Digital Logic and Design(DLD) subject has high importance in GATE CSE exam because:moderate number of questions nearly 6-7% of the total papersignificant weightage (6-7 marks) across multiple years This can be seen in the table given below:YearApprox. Marks from Digital LogicNumber of QuestionsD 2 min read Practice Questions - Digital Logic & Design Like