We will learn the basics of combinational as well as sequential logic. Next states and outputs are functions of inputs and present states of storage elements 54 two types of sequential circuits. Digital electronics part i combinational and sequential. Srinivasan department of electrical engineeringiit madras.
Sequential logic enables us to do more with less components. Consequently the output is solely a function of the current inputs. Array multiplier introduction to sequential circuits sr,jk and d flip flops jk and t flip flops triggering mechanisms of flip flops and counters updown counters shift registers application of shift registers state machines design of synchronous sequential. To learn simple digital circuits in preparation for computer engineering. Ripple counter increased delay as in ripplecarry adders delay proportional to the number of bits. In sequential circuits, the state of the circuit is crucial in determining the output values. Sequential circuits the digital circuits we have seen so far gates, multiplexer, demultiplexer, encoders, decoders are combinatorial in nature, i. That means sequential circuits include memory elements which are capable of.
Today well talk about sequential circuit analysis and design. Vlsi design low power memory circuits exam study material. Digital circuits and systems nptel online videos, courses. The fundamental principles of sequential logic show us how to construct circuits that switch from one operating point to the other. Sequential circuit analysis last time we started talking about latches and flipflops, which are basic onebit memory units.
Download be8251 basic electrical and electronics engineering lecture notes, books, syllabus parta 2 marks with answers be8251 basic electrical and electronics engineering important partb 16 marks questions, pdf books, question bank with answers key. Less hardware or more speed some things cannot be accomplished by combinational logic counter design. Design methodology, system modeling, hardwaresoftware codesign. Arithmetic with number systems, signed and unsigned number systems and their arithmetic. Autumn 2003 cse370 vi sequentai llogci 1 sequential logic sequential circuits simple circuits with feedback latches edgetriggered flipflops timing methodologies cascading flipflops for proper operation clock skew asynchronous inputs metastability and synchronization basic registers shift registers simple counters hardware description languages and sequential logic. This chapter explains how to do vhdl programming for sequential circuits. Digital circuits and systems online course video lectures by. Digital electronics and logic design tutorials geeksforgeeks. For a given input combination, a sequential circuit may produce different. Asynchronous circuits that can change the state immediately when enabled.
Nptel video lectures, iit video lectures online, nptel youtube lectures. Sequential circuits until now, circuits were combinational when inputs change, the outputs change after a while time logic delay thru circuit combinational circuit inputs outputs we want the clock to act like a start and stop signal a latch is a storage device. Flip flop is a sequential circuit which generally samples its inputs and changes its outputs only. Hence the previous state of input does not have any effect on the present state of the. Sequential circuits until now, circuits were combinational when inputs change, the outputs change after a while time logic delay thru circuit combinational circuit inputs outputs we want the clock to act like a start and stop signal a latch is a storage device that stores its inputs at a rising clock edge and. These circuits are faster than synchronous sequential circuits because there is clock pulse and change their state immediately when there is a change in the. Pdf be8251 basic electrical and electronics engineering. Module outcomes 1 able to draw state diagrams 2 sequential circuit design and analysis able to analyze synchronous sequential.
Now if d changes its value while clk 1, since r 0, we will still have z 1 and it will not change the value of r. In other words, a sequential circuit has a memory of its past state whereas a combinatorial circuit has no memory. Two useful states s1, r0 set state q will become to 1. Consist of a combinational circuit to which storage elements are connected to form a feedback path. Vhdl programming for sequential circuits tutorialspoint. Sequential circuits a sequential circuit consists of a combinational circuit and a feedback through the storage elements in the circuit. Digital electronics state assignment exam study material for. Types of sequential circuits there are two types of sequential circuit. Oct 26, 2012 sequential circuits outputs depend on present inputs and previous inputs also it contains memory elements for storing previous state inputs examples of sequential circuits are flip flops, counters, shift registers 4. Sequential circuits can be categorized as being synchronous or asynchronous.
Anand kumar the new edition of this wellreceived text continues to provide coherent and comprehensive coverage of digital circuits. Latches sr latch, d latch, flip flops d flip flop, jk flip flop, t flip. First, well see how to analyze and describe sequential circuits. Sequential circuits together with combinatorial circuits make it possible to. Digital circuits and systems nptel online videos, courses iit. For a given input combination, a sequential circuit may produce different output values, depending on its previous state. Flip flop is a sequential circuit which generally samples its inputs and changes its outputs only at particular instants of time and not continuously. Vlsi design low power memory circuits exam study material for. Definition of state machines, state machine as a sequential controller. Sequential logic sequential circuits simple circuits with feedback latches edgetriggered flipflops timing methodologies cascading flipflops for proper operation clock skew asynchronous inputs metastability and synchronization basic registers shift registers simple counters hardware description languages and sequential logic. Sequential circuits outputs depend on present inputs and previous inputs also it contains memory elements for storing previous state inputs examples of sequential circuits are flip flops, counters, shift registers 4.
Sequential circuits the combinational circuit does not use any memory. Computer science and engineering digital systems nptel. Dec 17, 2007 40 videos play all electronics digital circuits and systems nptelhrd for the love of physics walter lewin may 16, 2011 duration. Gate preparation, nptel video lecture dvd, electronicsandcommunicationengineering, vlsidesign, lowpowermemorycircuits, nmos transistors, pmos transistors, mos process parameters, cmos process parameters, cmos electrical properties, cmos device modeling, scaling principles, fundamental limits, cmos inverter scaling, cmos propagation delays, stick diagram, cmos layout diagrams. Sequential circuits cmos vlsi design slide 8 typical layout densities qtypical numbers of highquality layout qderate by 2 for class projects to allow routing and some sloppy layout. Input signals change one at a time and only when the circuit is in the stable state.
Easy to build using jk flipflops use the jk 11 to toggle. Digital electronics state assignment exam study material. Sequential circuits consist of a combinational circuit to which storage elements are connected to form a feedback path specified by a time sequence of inputs, outputs, and internal states two types of sequential circuits. A sequential circuit combinational logic circuit that consists of inputs variable x, logic gates computational circuit, and output variable z combinational circuit produces an output based on input variable only, but sequential circuit produces an output based on current input and previous input variables. Binary counters simple design b bits can count from 0 to 2b.
Srinivasan, department of electrical engineering, iit madras. It is designed for the undergraduate students pursuing courses in areas of engineering disciplines such as electrical and electronics, electronics and communication, electronics and instrumentation. Srinivasan, department of electrical engineering, iit madras for more details on nptel. Digital electronics part i combinational and sequential logic. Countingincrementing a number requires memory to accomplish steps to design sequential circuits. Srinivasan, department of electrical engineering, iit madras for more details on nptel visit. Later, we will study circuits having a stored internal state, i. It introduces the basic tools for design with combinational and sequential digital logic and state machines. Digital circuits department of electrical engineering, iit bombay. If d 0 when clk becomes 1, r changes to 0 since s 1, z 1, clk 1 and this resets the flipflop, making q 0.
Not practical for use in synchronous sequential circuits. Difference between combinational and sequential circuits, flip flops, counters, shift registers and pla. Srinivasan department of electrical engineering, iit madras. Aghdam 6s and r are equal to 1 while clk 0 which causes no change in the output. In sequential circuits, the \state of the circuit is crucial in determining the output values. In this course material we design and analyze only synchronous sequential logic. Digital circuits and systems online course video lectures. This type of circuits uses previous input, output, clock and a memory element. Which sequential circuits generate the feedback path due to the crosscoupled connection from output of one gate to the input of another gate.
The behavior is dependent on the arrangement of the input signal that changes continuously over time, and the output can be a change at any time clockless. A synchronous sequential circuit usually has a clock pulse clocked sequential circuits. For a given input combination, a sequential circuit may produce di erent output values, depending on its previous state. This will be followed by combinational and sequential circuit design. Srinivasan, department of electrical engineering, iit madras for more details on nptel visit nptel. Sample of the study material part of chapter 5 combinational. Synchronous asynchronous primary difference 94 synchronous vs.
Output is a function of both the present state and the input. A circuit with two crosscoupled nor gates or two crosscoupled nand gates. Asynchronous asynchronous sequential circuits internal states can change at any. Lecture 24 design of synchronous sequential circuits.
It is designed for the undergraduate students pursuing courses in areas of engineering disciplines such as electrical and electronics, electronics and. Structural design of sequential circuits better understanding and a better choice of states, the same problem might well be trivial. But sequential circuit has memory so output can vary based on input. Nptel syllabus digital circuits and systems video course 1. Asynchronous sequential circuit these circuit do not use a clock signal but uses the pulses of the inputs. Avoid to use latches as possible in synchronous sequential circuits to avoid design problems 58 sr latch. Whereas it is relatively straightforward to describe sequential circuit structure and define applicable engineering. Sequential circuits slide 8cmos vlsi design typical layout densities typical numbers of highquality layout derate by 2 for class projects to allow routing and some sloppy layout. Lecture 16 introduction to sequential circuits youtube.