Digital System Design Lab Manual (08.408 Btech Cse Kerala University)

08.408 Digital System Design Lab

DIGITAL SYSTEM DESIGN LAB MANUAL FOR IV SEMESTER B.TECH (CSE)

VALIYA KOONAMBAYIKULATHAMMA COLLEGE OF ENGINEERING AND TECHNOLOGY

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DECEMBER, 2013

Department of ECE, VKCET

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List of Experiments Expt. No. 1 2 3 4 5 6

Name of expt.

Study of digital IC and trainer kit Realization of Logic Circuits using basic gates. Half adder and full adder using gates and ICs Flip-Flops using gates Shift Registers Multiplexers and Demultiplexers using gates and ICs

7

Realization of combinational circuits using multiplexer/demultiplexer multiplexer/demul tiplexer ICs

8 9 10 11 12 13

Asynchronous counters using flip flops and ICs Synchronous counter Ring counters and Johnson counter using flip flops and ICs Four-bit magnitude comparator BCD to Decimal and BCD to 7-segment decoder & display Astable and monostable multivibrators multivibrato rs using ICs


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EXPT. NO. 1: STUDY S TUDY OF TRAINER KIT AND DIGITAL ICS AIM: a) To familiarize digital IC trainer kit b) To familiarize familiarize basic basic logic gates and universal gate gate ICs, and verify its truth table table COMPONENTS & EQUIPMENTS REQUIRED: 1. Digital IC Trainer kit 2. Connecting wires 3. Bread board (If required) 4. Multimeter – Multimeter – 1 1 No. 5. IC’s – 7404, 7404, 7408, 7432, 7400, 7402, 7486 and 7410 (1 No. each) THEORY: IC Trainer Kit Digital IC Trainer has been designed with the idea of providing basic facilities essential for conducting simple experiments in the laboratory. Using these facilities one can get oneself familiarized with the various digital ICs and circuits. The system is suitable for conducting experiments on TTL as well as CMOS ICs. Different sections sections in trainer kit are shown the figure 1 (left page).

Figure. 1. Block diagram of trainer kit


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Picture. 1. Trainer kit (make: Kitek) The features and functions of different sections in the kit are: 1. Bread board: For connecting circuit diagram 2. Seven segment display: Four 7-segment displays can be used with the experiments involving displays. Each display has individual segment control. 3. Logic level indicator: 10-LEDs for indicating output. The Logic high is indicating by LED glowing, where the logic low is indicated by LED is not glowing. Logic level output is given in 2mm banana socket provided on-board. 4. Potentiometer bank : Three pots of 1k, 10k and 100k variable resistors. 5. Function generator: Sine, triangular and square wave output with varying frequency up to 30kHz. Varying amplitude for sine and triangular waves and fixed amplitude for square wave. Also have different fixed frequency range 20Hz, 200Hz, 2 kHz, 20 kHz, 200 kHz and 1 MHz. 6. Logic level input: Ten push key switches to generate ten logic inputs. When the switch is in normal mode, logic level high will generated and when the switch is in push mode, logic level Low will will be generated on the 2mm banana socket provided on the kit. There There are are 10 Bi-Color LEDs used to indicate the logic input generated by each Push Key switch. The logic high is indicated by the corresponding LED glowing as RED where the Logic low is indicated by the LED glowing as GREEN. 7. Manual pulser: Generates a manual clock, whenever the push button switch is pressed and released. The pulse can be tapped from 2mm terminals marked as H-L-H Transition & L-H-L Transition for – for – ve ve edge and +ve edge clock pulse respectively. 8. AC power supply: 15V-0-15V ac power supply 9. Fixed power supply: +12V, -12V and +5V dc power supply Department of ECE, VKCET

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10. Varying power supply: -1.2V to -15V, +1.2V to +15V varying dc power supply 11. Fixed clock : Generate clock pulse of 1Hz, 10Hz, 100Hz, 1kHz, 10kHz, 100kHz and 1MHz fixed frequencies 12. Logic probe: Logics in the circuits can test by this probe. Logic high by Red LED and logic low by Green LED Logic gates: Logic gates process signals which represent true or false. Gates have one or more inputs and one output. Logic gates are available on special ICs (chips) which usually contain several gates of the same type. There are several several families of logic ICs and they can be split into two groups: TTL family – 74xx series and CMOS family – family – 40xx 40xx series. In the lab 74xx series ICs are using. Basic logic gate are: 1. NOT gate (inverter) ′

The output Y is true when the input A is NOT true, the output is the inverse of the input:  =  . A NOT gate is also called an inverter. The symbol, pinout diagram, diagram, pin functions and truth table of the NOT gate IC 7404 are shown in figure figure 2.

Figure. 2. NOT gate symbol, IC 7404 Pinout Diagram and Truth Table 2. AND gate The output Y is true if input A and B are both true: Q = A.B. An AND gate can have two or more inputs, its output is true if all inputs are true. The symbol, pinout diagram, pin functions and truth table of the 2-input AND gate IC 7408 are shown in figure 3.

Figure. 3. AND gate symbol, IC 7408 Pinout Diagram and Truth Table


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3. OR gate The output Y is true if either input A or input B is true, or both of them are true: Y = A + B. An OR gate can have two or more inputs, its output is true if at least one input is true. The symbol, pinout diagram, pin functions and truth table of the 2-input OR gate IC 7432 are shown in figure 4.

Figure. 4. OR gate symbol, IC 7432 Pinout Diagram and Truth Table 4. NAND gate This is an AND gate with the output inverted. The output of NAND is true if any one input is not  .  . A NAND gate can have two or more inputs; its output is true if NOT all inputs are true:  =  true. The symbol, pinout diagram, pin functions and truth table of the 2-input NAND gate IC 7400 are shown in figure 5.

Figure. 5. NAND gate symbol, IC 7400 Pinout Diagram and Truth Table The symbol, pinout diagram, pin functions and truth table of the 3-input NAND gate IC 7410 are shown in figure 6.


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Figure. 6. Three input NAND gate symbol, IC 7410 Pinout Diagram and Truth Table 5. NOR gate gate This is an OR gate with the output inverted. The output Y is true inputs A and B are false:  + . A NOR gate can have two or more inputs, its output is true if no inputs are true. The  =  symbol, pinout diagram, pin functions and truth table of the 2-input NOR gate IC 7400 are shown in figure 7.

Figure. 7. NOR gate symbol, IC 7402 Pinout Diagram and Truth Table 6. X-OR (EXclusive-OR) gate The output Y is true if either input A is true OR input B is true, but not when both of them are true:  =    . This is like an OR gate but excluding both inputs being true. The output is true if inputs A and B are different. X-OR gates can only have 2 inputs. The symbol, pinout diagram, pin functions and truth table of the 2-input X-OR gate IC 7486 are shown in figure 8.

Figure. 8. XOR gate symbol, IC 7486 Pinout Diagram and Truth Table PROCEDURE: 1. Place the IC on trainer kit. 2. Wire the circuit diagram 3. Connect VCC and GND to respective pins of trainer kit. 4. Connect the inputs to the input switches provided in the trainer kit. 5. Connect the outputs to the terminals of output LEDs. 6. Apply various combinations of inputs according to the truth table and observe condition of LEDs. RESULT:


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EXPT. NO. 2: REALIZATION OF LOGIC CIRCUITS USING BASIC GATES AIM:

a) To realize basic gates using universal gates. b) To verify Demorgan’s theorem. c) To verify a SOP & POS expression using universal gates. COMPONENTS & EQUIPMENTS REQUIRED: 1. Digital IC Trainer kit 2. Connecting wires 3. Bread board (If required) 4. Multimeter 5. ICs a) 7400 - 2 Nos. b) 7402 – 7402 – 2 2 Nos. THEORY: The universal property of NAND and NOR gates: NAND and NOR gates is said to be universal gates because any digital circuit can be implemented using only one of these gates. Digital circuits are frequently constructed with only NAND or NOR gates; because these gates are easier to fabricate with electronic electronic components. components. Because Because of the importance of NAND and NOR in the design of digital circuits, rules and procedures have been developed for the conversion from Boolean functions in terms of AND, OR and NOT into equivalent NAND or NOR logic diagrams diagrams . 1) Implementing inverter using NAND gate:

 . One NAND input pin is If all NAND input pins connect to the input signal X gives an output  connected to the input signal x while all other input pins are connected to logic 1, the output will be  . ie,  .  =  . The circuit of inverter using NAND is shown in figure 1. 

Figure. 1. Inverter using NAND and truth table 2) Implementing AND using NAND gates: An AND gate can be replaced by NAND gates as shown in the figure 2. The AND is replaced by

 .  = .  a NAND gate with its output complemented by a NAND gate inverter. ie, 


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Figure. 2. AND using NAND and truth table 3) Implementing OR using NAND gates: An OR gate can be replaced by NAND gates as shown in the figure 3. The OR gate is replaced by

 .  =  +  =  +  (By a NAND gate with all its inputs complemented by NAND gate inverters. ie  DeMorgan’s law) law)

Figure. 3. OR using NAND and truth table 4) Implementing NOR using NAND gate: A NOR gate can be replaced by NAND gates as shown in the figure 4. The NOR gate is replaced by a NAND gate with all all its inputs complemented complemented by NAND gate inverters inverters and complementing complementing its output

    .  =  by NAND inverter. inverter. ie,  .  =  +  (By DeMorgan’s law)

Figure. 4. NOR using NAND and truth table 5) Implementing XOR using NAND gate: An XOR gate can be replaced by NAND gates as shown in the figure 5. We know,  =

     =   +  =   +  +  +  =   +   +   =   +         (    +     =    +     =   ) (By (By DeMorgan’s law) law) =  ( ).     This can be implemented by four NAND gates.

Figure. 5. XOR using minimum number NAND gates and truth table


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6) Implementing inverter using NOR gate:

 . One NOR input pin is If all NOR input pins connect to the input signal X gives an output  connected to the input signal x while all other input pins are connected to logic 0, the output will be  . ie,  +  =  . The circuit of inverter using NOR is shown in figure 6. 

Figure. 6. Inverter using NOR and truth table 7) Implementing AND using NOR gate: An AND gate can be replaced by NOR gates as shown in the figure 7. The AND gate is replaced

 +  =  (by DeMorgan’s by a NOR gate with all its inputs complemented complemented by NOR gate inverters. ie  law)

Figure. 7. AND using NOR and truth table 8) Implementing OR using NOR gate: An OR gate can be replaced by NOR gates as shown in the figure 8. The OR is replaced by a

 +  =  +  NOR gate with its output output complemented complemented by a NOR gate inverter. inverter. ie, 

Figure. 8. OR using NOR and truth table DeMorgan’s DeMorgan’s theorem: It is used to simplify boolean equations. The theorems are:

 +  =  .  1.   =  +  2.  The circuit diagram to prove these theorems are shown in figure 9 and figure 10. Department of ECE, VKCET

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Figure. 9. Circuit for DeMorgan’s Theorem 1 and truth table.

Figure. 10. Circuit Circu it for DeMorgan’s Theorem 2 and truth table. Sum of Product (SOP) expression: Each product term in the SOP expression is called minterm. SOP expression can be economically

 . By realized by universal NAND gates. Consider a two variable SOP expression,  =  +   

 +      .   =   . This expression can be economically implemented by 5 DeMorgan’s theorem,  =  NAND gates as shown in figure 11. 11.

Figure. 11. SOP implementation using NAND and truth table. Department of ECE, VKCET

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Product of Sum (POS) expression: Each sum term in the POS expression is called maxterm. POS expression can be economically

 ). By realized by universal NOR gates. Consider a two variable POS expression,  =   + . (   +  

  +   ). This expression can be economically  ) = (  + ) + (  DeMorgan’s theorem,  =   + . (   +  implemented implemented by 5 NOR gates as shown in figure 12.

PROCEDURE: 1. Place the ICs on trainer kit. 2. Wire the circuit diagram. 3. Connect VCC and GND to respective pins of trainer kit. 4. Connect the inputs to the input switches provided in the trainer kit. 5. Connect the outputs to the terminals of output LEDs. 6. Apply various combinations combinations of inputs according to the truth table and observe condition of LEDs. RESULTS:


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EXPT. NO. 3: ARITHMETIC CIRCUITS CIRCUITS USING GATES AND ICs AIM: a) b) c) d)

To design and setup the half adder using basic gates and universal gates. To design and setup full adder using basic gates and universal gates. To design and setup 4-bit adder/subtractor using IC-7483 To design and setup single digit BCD adder using IC-7483

COMPONENTS REQUIRED: 1. Digital IC Trainer kit 2. Connecting wires 3. Bread board (If required) 4. Multimeter 5. ICs a) 7400 – 7400 – 3 3 Nos. b) 7408 – 7408 – 1 1 No. c) 7432 – 7432 – 1 1 N0. d) 7486 – 7486 – 2 2 Nos. e) 7483 – 7483 – 2 2 Nos. THEORY: Half-Adder: A combinational logic circuit that performs the addition of two data bits A and B is called halfadder. Addition will result in two output bits; one of which is the sum bit S, and the other is the carry bit C. The Boolean functions describing the half adder are:

 =   = .  The symbol, truth table, K-Maps and circuit diagrams for half-adder is shown in figure 1.

Figure. 1. Half-adder symbol, truth table, K-Maps and circuit diagrams.


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Full-Adder: The half-adder does not take the carry bit from its previous stage into account. This carry bit from its previous stage is called carry-in bit. A combinational logic circuit that adds two data bits A and B, and a carry-in bit C in is called a full-adder. Addition in this adder will result in two output bits; one of which is the sum S, and the other is the carry out C out. The Boolean functions describing for full-adder are:



 =  =  +  +  or

 = ( ) +  The second expression for C out can be realized by minimum number of gates. The C out is high only either Cin is high AND, A and B are different OR A AND B is high. The symbol, truth table, K-Maps and circuit diagrams for full-adder is shown in figure 2.

Figure. 2.a Symbol, truth table and K-Maps for full-adder

Figure. 2.b. Circuit diagram using basic gates for full-adder


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Figure. 2.c. Circuit diagram using NAND gates for full-adder Four-bit adder/subtractor using IC-7483: IC-7483 is adder/subtractor IC used to perform arithmetic operation. The pinout diagram and pin functions of IC-7483 is shown in figure 3.a.

Figure. 3.a. Pinout diagram and pin functions of IC-7483 The adder/subtractor circuit using IC-7483 is shown in figure 3.b. Here XOR gates are used as controlled buffer or inverter. Binary numbers can be subtract by taking 2’s complement of subtrahend. To add 4-bit numbers A 3A2A1A0 and B3B2B1B0, the XOR gates behaves as buffer by making SUB as 0. To subtract 4-bit numbers, the XOR gates behaves as inverter by making SUB as 1 and B 3B2B1B0 is complemented and added with 1 by C in.

Figure.3.b. 4-bit adder/subtractor using IC-7483 Department of ECE, VKCET

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Observed results:

Single digit BCD adder using IC-7483: In BCD addition, if the sum exceeds 9, the result must be added to the 6 to convert the result into BCD number. For this two 7483 ICs are required: one for binary addition and other for the addition of a combinational combinational circuit set up which generate 6, if output of first adder is more than 9 and the sum from the first. The truth table and K-Map to design BCD adder is shown in figure 4.a. The X bit can be used to generate 6 (0110)2. The circuit diagram is shown in figure 4.b.

Figure.4.a. Truth table and K-Map for single digit BCD adder


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Figure.4.b. Single digit BCD adder Observed results:



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EXPT. NO. 4: FLIP FLOPS USING GATES AND ICs AIM:

To realize SR, D, T, JK and master-slave JK flip flops using gates and ICs. COMPONENTS REQUIRED: 1. Digital IC Trainer kit 2. Connecting wires 3. Bread board (If required) 4. Multimeter 5. ICs a) 7400 – 7400 – 3 3 Nos. b) 7410 – 7410 – 2 2 Nos. c) 7404 – 7404 – 1 1 No. d) 7476 – 7476 – 1 1 No. e) 7474 – 7474 – 1 1 No. THEORY: Latches and flip-flops are the basic elements for storing information. One latch or flip-flop can store one bit of information. The main difference between latches and flip-flops is that for latches, their outputs are changed according to the input. But in flip-flops, the output changes only either at the rising or falling edge of the clock signal. There are basically four main types of latches and flip-flops: SR, D, T and JK. The major differences in these flip-flop types are the number of inputs they have and how they change state. SR latch: The symbol, circuit diagram and truth table with states of SR latch with enable input E is shown in figure 1.

Figure.1. Symbol, circuit diagram and truth table of SR latch with enable input. Here the output is disabling when enable input E is 0. The output remains previous state which depends on its S (Set) and R (Reset) inputs. The latch is enabled by setting E as 1. When input S is 0 and input R is 1, latch goes to reset state. Then the present output Q n+1 goes to 0. When S input is 1 and R input is 0, latch goes to set state and the present output Q n+1 goes to 1. When both input S and R are 0, Department of ECE, VKCET

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latch goes to hold state and present output  +1 =  , where Q n is previous output. When both input S  +1 = 1. and R are 1, latch goes to invalid state, output and its complement output is 1, ie  +1 =  SR flip flop: The symbol, circuit diagram and truth table with states of +ve edge triggered SR flip flop is shown in figure 2.

Figure.2. Symbol, circuit diagram and truth table of +ve edge triggered SR flip flop The operation of SR flip flop is same as SR latch, but the difference is output changes only during the +ve edge of clock input signal CLK.   The characteristics equation of SR flip flop is  +1 =  +  JK flip flop: The symbol, circuit diagram and truth table with states of +ve edge triggered JK flip flop is shown in figure 3.

Figure.3. Symbol, circuit diagram and truth table of JK flip flop using gates This flip flop is similar to SR flip flop, but the invalid state of SR flip flop is avoided here. J is set input similar to S and K is reset input similar to R. The invalid state is eliminated by feedback  to input K and J inputs respectively by 3-input NAND gates. When clock pulse arrangement of  and  CLK is 0, the flip flop hold the previous state. When J is 0 and K is 1, the flip flop goes to reset state during +ve edge of clock pulse. Then present output Q n+1 goes to 0. When J is 1 and K is 0, the flip flop goes to its set state during +ve edge of clock pulse and the present output Q n+1 becomes 1. When both J and K are 0, flip flop goes to the hold state during +ve edge of clock and the present output Q n+1 = Q n, When both input J and K are 1, flip flop goes to toggle state during +ve edge of clock, ie  +1 =  .  +   The characteristics characteristics equation of JK flip flop is  +1 =  


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D flip flop The symbol, circuit diagram and truth table with states of +ve edge triggered D flip flop using gates is shown in figure 4.

Figure.4. Symbol, circuit diagram and truth table of D flip flop using gates. D flip flop or Data flip flop uses SR flip flop, but the hold and invalid states are avoided. Here the reset and set states are used to store input and transfer it to the output during the edge of clock pulse. When clock pulse is 0, flip flop goes to hold state. When D is 0, the flip flop goes to its reset state and output Q becomes 0 during the +ve edge of clock pulse. When D is 1, the flip flop goes to its set state and output Q becomes 1 during the – the – ve ve edge of clock pulse. The characteristics equation of D flip flop is  +1 =  T flip flop: The symbol, circuit diagram and truth table with states of +ve edge triggered T flip flop using gates is shown in figure 5.

Figure.5. Symbol, circuit diagram and truth table of T flip flop using gates T flip flop or Toggle flip flop uses JK flip flop, but the set and reset states are avoided. When clock pulse is 0, flip flop goes to hold state. When T input is 0, flip flop goes to hold state during the +ve edge of clock pulse and the present output  +1 =  . When T input is 1, flip flop goes to toggle state

 . during the +ve edge of clock pulse and the present output  +1 =  The characteristics characteristics equation of T flip flop is  +1 =   


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Master-slave JK flip flop: The circuit diagram and truth table of master-slave master-slave JK flip flop using gates are shown in figure 6.

Figure.6. Master-slave JK flip flop using gates The master slave flip flop is used as a solution to the race around problem in flip flops. In the JK latch, the output is feedback to the input, and therefore changes in the output results change in the input. Due to this in the positive half of the clock pulse if J and K are both high then output toggles continuously. This condition is known as race around condition. To avoid race around condition, different methods are: 1. Keep clock pulse smaller than the propagation delay. 2. Using master-slave flip flop. 3. Using positive or negative edge triggering. The master-slave JK flip flop consists of two flip flops: one is called master which is enabled by clock pulse first and other is called slave enabled by inverted clock pulse. During +ve edge of clock, master is active and slave is disable. Then m aster’s state depends on J and K input and slave goes to hold state. During the – ve ve edge of clock, master is disable and slave is active. Then master hold previous output, which transferred to slave input and its state depends on master output. Flip flops using ICs: JK flip flop IC: The pinout diagram, pin functions of dual, -ve edge triggered JK flip flop IC-7476 is shown in figure 4.a.

Figure.4.a. Pinout diagram and pin functions of IC-7476 Department of ECE, VKCET

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Figure.4.b. Circuit diagram and truth table of JK flip flop using IC-7476 D flip flop: The pinout diagram, pin functions of dual, +ve edge triggered D flip flop IC 7474 is shown in figure 6.a.

Figure 6.a. Pinout diagram and pin functions of IC-7474 The circuit and its truth table is shown if figure 6.b.

Figure.6.b. Circuit Circuit diagram and truth table of D flip flop using IC-7474


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T flip flop: The circuit diagram and truth table of T flip flop using JK flip flop IC-7476 is shown in figure 7.

Figure.7. Circuit diagram diagram and truth table of T flip flop using IC 7476 PROCEDURE: 1. Place the ICs on trainer kit. 2. Wire the circuit diagram. 3. Connect VCC and GND to respective pins of trainer kit. 4. Connect the inputs to the input switches provided in the trainer kit. 5. Connect the outputs to the terminals of output LEDs. 6. Apply various combinations combinations of inputs according to the truth table and observe condition of LEDs. RESULT:

Viva questions: 1. Differentiate latches and flip flops.(2 marks) 2. Draw the SR latch and flip flop using using NOR gates. (2 marks) 3. Construct SR flip flop using JK flip flop (1 mark)


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EXPT. No. 5: SHIFT REGISTERS AIM:

To realize different shift registers. COMPONENTS REQUIRED: 1. Digital IC Trainer kit 2. Connecting wires 3. Bread board (If required) 4. ICs a) 7474 – 7474 – 2 2 Nos. b) 7432 – 7432 – 1 1 No. THEORY: Shift register is a type of sequential logic circuit that is used for the storage or transfer of data in the form of binary numbers. It shifts the data out once every clock cycle, hence the name shift register. It basically consists consists of several single bit D flip flops, one for each bit (0 or 1) connected together together in a serial or daisy-chain arrangement so that the output from one flip flop becomes the input of the next latch and so on. The number of individual D flip flops required to make up a single shift register is determined by the number of bits to be stored. In general, n-bit can be stored by individual data flip flops. Shift registers are used for data storage or data movement and are used in computers. Usually to convert the data from either a serial to parallel or parallel to serial format. The individual D flip flops that make up a single shift register are all driven by a common clock signal CLK, making them synchronous devices. Generally, shift registers operate in one of four different modes. They are: a. Serial-In Serial-Out (SISO) b. Serial-In Parallel-Out (SIPO) c. Parallel-In Parallel-In Serial-Out (PISO) d. Parallel-In Parallel-In Parallel-Out Parallel-Out (PIPO) SISO shift register: The circuit diagram of serial-in serial-out shift register is shown in f igure 1.a.

Figure.1.a. Four bit-Se bit-Serial-In rial-In Serial-Out Shift Register using D flip flop IC 7474 Each D flip flop store one bit, hence require four flip flops for 4-bit shift register. The output of one flip flop is connected to input to the next and for each clock the input state is shifted to the output. Then for +ve edge of each clock pulse: Q 3 = D3, Q2 = Q3, Q1 = Q2 and Q0 = Q1. If we connect serial input Department of ECE, VKCET

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Sin as D3 and take serial output S out from Q0, the circuit out serial data in to serial out for each clock pulse. These arrangements are for left shift and for right shift, organize the bits in opposite direction. The truth table of serial-in serial-out shift register is shown in figure 1.b.

Figure.1.b. Truth table of Serial-In Serial-In Serial-Out shift register. Observed results: (In left page) Serial input data S in = 1011

SIPO shift register: The circuit diagram of serial-in parallel-out shift register is shown in figure 2.a.

Figure.2.a. Four-bit Serial-In Parallel-Out Shift Register using D flip flop IC 7474 The circuit is similar to SISO, but the parallel output is obtained from the output of each flip flop. So during the fourth clock pulse the parallel data is available at Q 3Q2Q1Q0. The truth table of serial-in parallel-out parallel-out is shown in figure 2.b.


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Figure.2.b. Truth table of Serial-In Parallel-Out shift register Observed results: (In left page) Serial input data S in = 1010

PISO shift register: The circuit diagram of serial-in parallel-out shift register is shown in figure 3.a.

Figure.3.a. Four-bit Parallel-In Serial-Out shift register using D flip flop IC 7474 Here 4-bit parallel inputs P 3 to P0 are loaded to each flip flop through OR gate initially. After loading input to each flip flop, all inputs are set as 0. The output state of each flip flop is fed to input of next stage by ORing with the parallel input. The truth table of parallel-in serial-out shift register is shown in figure 3.b.


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Figure.3.b. Truth table of Parallel-In Parallel-In Serial-Out shift r egister Observed results: (In left page) Parallel input data P = 1010

PIPO shift register: The circuit diagram of parallel-in parallel-out parallel-out shift register is shown in figure 4.a.

Figure.4.a. Parallel-In Parallel-Out shift register using D flip flop IC 7474 Here 4-bit parallel inputs P 3 to P 0 are directly connected to the input of flip flops. For the clock input each input bit are shifted to output and are taken as parallel output bits Q 3 to Q0. The truth table for parallel-in parallel-out parallel-out shift register register is shown shown in figure 4.b.

Figure.4.b. Truth table of Parallel-In Parallel-In Parallel-Out shift register


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Observed results: (In left page) Parallel input data i) P = 1101 ii) P = 0110

PROCEDURE: 1. Place the ICs on trainer kit. 2. Wire the circuit diagram. 3. Connect VCC and GND to respective pins of trainer kit. 4. Connect the inputs to the input switches provided in the trainer kit. 5. Connect the outputs to the terminals of output LEDs. 6. Apply various combinations of inputs according to the truth table and observe condition of LEDs. RESULT:

Viva questions: 1. Draw the circuit diagram of 4-bit serial-in serial-out shift register with left shift operation. (1 mark)

 input. (2 2. Draw the circuit diagram of 4-bit parallel-in serial-out shift register with load/shift marks) 3. Compare different shift registers. (1/2 mark) 4. Obtain 4-bit parallel-in serial-out serial-out shift register using JK flip flops (1 mark) 5. List out different applications of shift registers. (1/2 mark) (Hint for Q2) The general block diagram:

Where X is control circuit, FF is flip flop, P is parallel input, D is flip flop input and Q is output.


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 input. If M=0, shift operation otherwise it is Design of control circuit: M is mode control or load/shift load operation. During shift operation, operation, D3 = P3, D2 = Q3, D1 = Q2 and D0 = Q1. During load operation, D3 = P3, D2 = P2, D1 = P1 and D0 = P0. Develop truth table for X3, X2, X1 and X0. Draw K-map for each truth table and obtain Boolean expression for D3, D2, D1 and D0. Complete the X3, X2, X1 and X0 circuits with logic gates.


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EXPT. No. 6: MULTIPLEXERS AND DEMULTIPLEXERS USING GATES AND ICs AIM: a) To realize multiplexer and demultiplexer using basic gates b) To realize multiplexer and demultiplexer using ICs 74151 and 74138 respectively. COMPONENTS REQUIRED: 1. Digital IC Trainer kit 2. Connecting wires 3. Bread board (If required) 4. ICs a) 7404 – 7404 – 2 2 Nos. b) 7411 – 7411 – 2 2 No. c) 7432 – 7432 – 1 1 No. d) 74151 – 74151 – 1 1 No. e) 74138 – 74138 – 1 1 No. THEORY: Multiplexer A multiplexer is a combinational circuit that selects binary information from one of many input lines and directs it to a single output line. The selection of a particular input line is controlled by a set of selection lines. Normally there are 2 n input lines and n selection lines whose bit combination determine which input is selected. The symbol and condensed truth table of 4x1 multiplexer are shown in figure 1.a.

Figure.1.a. Symbol and condensed truth table of 4 x 1 multiplexer Design of 4x1 multiplexer using basic gates From the condensed truth table, we can obtain the following Boolean expression for 4 x 1 multiplexer.

1 S 0 + D1 S1 S0 + D2 S1 S 0 + D3 S1 S0 Y = D0 S To implement this Boolean expression, 3 input AND gate is required. The pinout diagram of 3 input AND gate IC 7411 is shown in figure 1.b.


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Figure.1.b. Pinout diagram of IC 7411 The circuit diagram of 4 x 1 multiplexer using basic gates is shown in figure 1.c.

Figure 1.c. Circuit diagram of 4 x 1 multiplexer using gates Observed results: (In left page)


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8 x 1 Multiplexer Multiplexer using IC 74151 The pinout diagram, functions of pins and truth table of 8 x 1 multiplexer IC 74151 are shown in figure 1.d.

Figure.1.d. Pinout diagram, diagram, functions of pins and condensed truth table for IC 74151 Observed results: (In left page)

Demultiplexer: Demultiplexer is a counter part of multiplexer and has one input and more than one output. It is used to send an input signal to one of many output lines according to the combination of selection lines. This is similar to a decoder, but a decoder is used to select among many outputs, while a demultiplexer is used to send a signal among many outputs. Normally there are 2 n output lines and n selection lines whose bits combination combination determines determines which output is selected. selected. The symbol and condensed truth trut h table of 1 x 4 demultiplexer are shown in figure 2.a.

Figure.2.a. Symbol and condensed truth table of 1 x 4 demultiplexer Department of ECE, VKCET

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Design of 1 x 4 demultiplexer using basic gates From the condensed truth table, the Boolean expressions for outputs are:

0 = 1  = 1 0 = 1  0 = 1 0 The circuit diagram of 1 x 4 demultiplexer using basic gates is shown in figure 2.b. 0 1 2 2

Figure 2.b. Circuit diagram of 1 x 4 demultiplexer using gates Observed results: (In left page)

1 x 8 Demultiplexer using IC 74138 The pinout diagram, functions of pins and truth table of 1 x 8 decoder/demultiplexer decoder/demultiplexer IC 74138 are shown in figure 2.c.


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Figure 2.c. Pinout diagram, functions of pins and truth table of IC 74138 The circuit diagram for 1 x 8 demultiplexer using IC 74138 is shown in figure 2.d. Here the active high enable input is using as data input.

Figure.2.d. Circuit Circuit diagram for 1 x 8 multiplexer multiplexer using IC 74138 Department of ECE, VKCET

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Observed results: (In left page)

PROCEDURE: 1. Place the ICs on trainer kit. 2. Wire the circuit. 3. Connect VCC and GND to respective pins of trainer kit. 4. Connect the inputs to the input switches provided in the trainer kit. 5. Connect the outputs to the terminals of output LEDs. 6. Apply various combinations of inputs according to the truth table and observe condition of LEDs. RESULT:

Viva questions: 1. Implement 8 x 1 multiplexer multiplexer using 4 x 1 multiplexers. multiplexers. (2 marks) 2. Differentiate multiplexers multiplexers and encoders. (1 mark) 3. How many select lines are required for 16 16 x 1 multiplexers and 1 x 32 demultiplexers. demultiplexers. (1mark) 4. Why multiplexers are called data selectors? (1 mark)


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EXPT. No. 7: REALIZATION OF COMBINATIONAL CIRCUITS USING MULTIPLEXER/DEMULTIPLEXER MULTIPLEXER/DEMULTIPLEX ER ICs AIM: To realize combinational circuits using multiplexer and demultiplexer ICs. COMPONENTS REQUIRED: 1. Digital IC Trainer kit 2. Connecting wires 3. Bread board (If required) 4. ICs a) 7404 – 7404 – 1 1 No. b) 74151 – 74151 – 1 1 No. c) 74138 – 74138 – 1 1 No. d) 7420 – 7420 – 1 1 No. THEORY: Combinational circuits using multiplexer ICs Any Boolean function of n-variables can be implemented using a multiplexer with n-1 selection lines. For that, the first n-1 input variables of the function will be connected to the selection lines and the nth input variable is evaluated according to the value of the minterms of the function. These evaluated values are connected to the data input lines. The implementation of a Boolean function

 , , ,  = (1, (1, 3,4, 11, 11, 12, 12, 13, 13, 14, 14, 15) 15) using 8 x 1 multiplexer IC- 74151 is shown in figure 1.

Figure 1.a. Truth table for the given Boolean function to implement by multiplexer Department of ECE, VKCET

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Figure 1.b. Circuit diagram for the given Boolean function using multiplexer IC 74151 Observed Truth Table: (In left page)

Combinational circuits using demultiplexer ICs A decoder/demultiplexer provides 2 n minterms of n input variables (select lines). Each output is asserted by a unique pattern of input variables. Any Boolean function can be expressed in SOP form and a decoder that generates the minterms of the function, together with external OR gates can produce the Department of ECE, VKCET

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required Boolean functions. This way, any combinational circuit with n inputs and m outputs can be implemented by 1 x 2 n demultiplexer (n x 2 n decoder) and m OR gates (if demultiplexer has active low output, use NAND gates). The implementation implementation of full adder using demultiplexer demultiplexer IC 74138 is shown in figure 2.

Figure.2.a. Truth table and Boolean functions of full adder Sum S is obtained by ORing Y 1, Y 2, Y 4 and Y7; carry out Cout is obtained by ORing Y 3, Y 5, Y 6 and Y7. In case of demultiplexer of active low output, use NAND gate instead of OR. The pin out diagram of IC 7420, circuit of full adder using demultiplexer IC 74138 and 7420 is shown in figure 2.b.

Figure.2.b. Pinout diagram of IC 7420 and circuit diagram of full adder using IC 74138 and 7420


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Observed Truth Table: (In left page)


Viva questions: 1. Design the following Boolean Boolean expressions using 8 x 1 multiplexer. multiplexer. i. , , ,  = (, , , , ) ii. , , ,  = (, , , , ) (2 marks) 2. Design a full subtractor subtractor using 1 x 8 demultiplexer. (2 marks) 3. Design a 3-bit binary to gray code converter by 1 x 8 demultiplexer. demultiplexer. (1 marks) Note: You can also expect expect basic questions questions from experiment experiment no.1 to 6


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EXPT. No. 8: ASYNCHRONOUS COUNTERS USING FLIP-FLOPS AND ICs AIM:

To realize asynchronous counters (ripple counter) using flip flops and ICs. COMPONENTS REQUIRED: 1. Digital IC Trainer kit 2. Connecting wires 3. Bread board (If required) 4. ICs a) 7476 – 7476 – 2 2 Nos. b) 7493 – 7493 – 1 1 No. c) 7486 – 7486 – 1 1 No. d) 7408 – 7408 – 1 1 No. THEORY Asynchronous counter using flip-flops Counter is a sequential circuit to produce a prescribed sequence of states according to the input pulses. The input pulse is clock pulse pulse and the sequence of states follows follows binary number sequences sequences or any other sequence. A counter that follow binary number sequences is called binary counter and an n-bit binary counter counter consists of of n flip-flops and and can count count in binary binary from 0 to 2 n – 1 1 and such a counter is called n Modulo-N (Mod-N) counter, counter, where N is the number of states and N = 2 . The binary counter with forward counting is called up-counter and reverse counting is called down-counter. One type of binary counter is ripple counter or asynchronous counter. In this the clock input is applied only to the f irst flip-flop and all subsequent flip-flops are clocked by the output of the preceding flip-flop. Due this rippling of flip-flops by clock pulses, the counter is called ripple counter. The circuit diagram and truth table of 2-bit asynchronous up-counter (Mod-4 counter) using JK flip-flop IC 7476 is shown in figure 1.


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Figure. 1. Two-bit asynchronous up-counter circuit circuit and truth table using JK flip-flop Here the JK flip-flop is using as T flip-flop by keeping its toggle state. For up-counting the output Q of first flip-flop is connected to clock input of next flip-flop. So the output of each flip-flop changes only during the – the – ve ve edge of the clock pulse. The circuit diagram and truth table of 2-bit asynchronous down-counter (Mod-4 counter) using JK flip-flop IC 7476 is shown in figure 2.

Figure. 2. Two-bit asynchronous down-counter circuit and truth table using JK flip-flop For down-counting the complement output Q of first flip-flop is connected to clock input of next flip-flop. So the output of next stage flip-flop change only during the +ve edge of the clock pulse and hence down-counting takes place. The circuit diagram and truth table of 2-bit asynchronous up/down-counter using JK flip-flop is shown in figure 3.

Figure.3. Two-bit asynchronous up/down-counter up/down-counter circuit and truth table using JK flip-flop Department of ECE, VKCET

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For up-counter, keep   / signal as 0, then XOR gate behaves as a buffer for clock pulse of next stage. For down-counter, keep   / signal is 1, then XOR gate behaves as inverter and complement the clock pulse to next stage. The advantage of the ripple counter is easy to implement, but the disadvantage is propagation delay depends on number of flip-flops. It is because of the rippling of clock from one stage to other. Asynchronous counter using ICs The pinout diagram and functions of pins 4-bit binary ripple counter IC 7493 is shown in figure 4.a.

Figure.4.a. Pinout diagram and pin functions of 4-bit binary counter IC 7493 The circuit diagram of 4-bit asynchronous binary up-counter (Mod-16 counter) using IC 7493 is shown in figure 4.b.


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Figure.4.b. Circuit diagram of 4-bit asynchronous counter using IC 7493  1 . The Here the output Q 0 (first flip-flop output) is connected connected to clock input of second flip-flop  clock input for the other flip-flops are internally connected in the IC. For counting, any one of the master reset MR 1 and MR 2 is set to 0. Design of mod-10 up-counter Given that N = 10. We have N = 2 n, where n is the number of bits/flip-flops in the counter.

ie, 2n = 10. Then  =

ln 10 ln 2

= 3.3

Therefore counter require more than 3 bit, and choose next integer 4. So we can choose 4-bit binary counter. The state diagram of mod-10 up-counter is shown in figure 5.a.

Figure 5.a. State diagram of mod-10 up-counter Consider the truth table of the 4-bit counter with master reset MR 1 as output and Q 3-Q0 as input to reset th th counter from its 9 state to 0 state. The truth table and K-map for MR 1 is shown in figure 5.b.

Figure.5.b. Truth table for mod-10 up-counter and K-map for MR 1 Department of ECE, VKCET

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Then the Boolean expression for MR 1 = Q3Q1. The circuit diagram and truth table for mod-10 up-counter using IC 7493 is shown in figure 5.c.

Figure.5.c. Circuit diagram and truth table of mod-10 up-counter using IC 7493 PROCEDURE: 1. Place the ICs on trainer kit. 2. Wire the circuit diagram. 3. Connect VCC and GND to respective pins of trainer kit. 4. Connect the inputs to the input switches provided in the trainer kit. 5. Connect the outputs to the terminals of output LEDs. 6. Apply various combinations combinations of inputs according to the truth table and observe condition of LEDs. RESULT:

Viva questions: 1. Draw the circuit diagram diagram of 4-bit ripple up-counter using flip-flops. (1 mark) 2. What is the propagation delay of n-bit ripple counter, if the delay of T flip- flops flip- flops is τ d d . (1mark) 3. Draw the pinout diagram diagram of IC-7493 and identify the pin functions. functions. (1 mark) 4. Design a mod-6 asynchronous down-counter. down-counter. (2 marks) Note: You can also expect basic questions from experiment experiment no.1 to 7, pinout diagram and pin functions of ICs used in the lab so far.


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EXPT. No. 9: SYNCHRONO S YNCHRONOUS US COUNTERS USING FLIP-FLOPS AND ICs AIM:

To realize synchronous counters using flip flops and ICs. COMPONENTS REQUIRED: 1. Digital IC Trainer kit 2. Connecting wires 3. Bread board (If required) 4. ICs a) 7476 – 7476 – 2 2 Nos. b) 7408 – 7408 – 1 1 No. c) 7486 – 7486 – 1 1 No. d) 74193 – 74193 – 1 1 No. THEORY: Synchronous counter using flip-flops This is another type of binary counter. In this the clock input is applied to all flip-flops, due to this all states change under the control of single clock. The operation of this counter is same as asynchronous counter, but this is faster one because all states are changed by a single clock. Design of 3-bit synchronous up-counter using flip-flops: For 3-bit counter, there are 2 3 = 8 states, hence it is also called mod-8 counter. The circuit require 3 flip-flops (prefer T). The state diagram, present and next state of truth tables along with the input of flip-flops and K-Maps for each T input is shown in figure 1.a. Here the T input for each flip-flop is obtained according according to the present and next state of the flip-flop. It may be either toggle state (T=1) or hold state (T=0).


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Figure 1.a. State diagram, truth table and K-maps for 3-bit (mod-8) synchronous up counter. The circuit diagram and truth table of 3-bit synchronous up-counter using flip-flops is shown in figure 1.b.

Figure 1.b. Circuit diagram and truth table of 3-bit synchronous up-counter using flip-flops


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Design of 3-bit synchronous down-counter using flip-flops: The state diagram, present and next state of truth tables along with the input of flip-flops and KMaps for each T input is shown in figure 2.a

Figure.2.a. State diagram, truth table and K-maps for 3-bit (mod-8) synchronous down-counter. The circuit diagram and truth table of 3-bit synchronous up-counter using flip-flops is shown in figure 2.b. and 2.c.

Figure.2.b. Circuit diagram of 3-bit synchronous down-counter using flip-flops


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Figure.2.c. Truth table of 3-bit synchronous down-counter down-counter using flip-flops Design of 2-bit synchronous up/down-counter up/down-counter using flip-flops: The state diagram, present and next state of truth tables along with the input of flip-flops and KMaps for each T input is shown in figure 3.a. Here an input M is used for up/down count action. If M = 0, up counting, else down counting is performed by the counter.

Figure.3.a. State diagram, diagram, truth table and K-maps for 2-bit (mod-4) synchronous up/down-counter. The circuit diagram and truth table of 2-bit synchronous up/down-counter using flip-flops is shown in figure 3.b.


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Figure.3.b. Circuit diagram and truth table of 2-bit synchronous up/down-counter using flip-flops Synchronous counter using ICs The pinout diagram and functions of pins 4-bit (Mod-16) binary synchronous counter counter IC 74193 is shown in figure 4.a.

Figure 4.a. Pinout diagram and pin functions of 4-bit binary synchronous counter IC-74193 The circuit diagram and truth table of 4-bit (Mod-16) synchronous up-counter using IC-74193 is shown in figure 4.b.

Figure 4.b. Circuit diagram and truth table of 4-bit synchronous up-counter up-counter using IC-74193 Department of ECE, VKCET

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Viva questions: 1. Design mod-14 synchronous up/down up/down counter using flip-flops. (2 marks) 2. Construct a circuit to divide a clock signal frequency of f by 4. (2 marks) 3. Design mod-16 counter using using mod-4 counters. (1 mark) Note: Prepare Prepare all ICs ICs pinout diagram diagram and and functions of each pins.


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EXPT. No. 10: RING COUNTER AND JOHNSON COUNTER USING FLIPFLOPS FLIPFLOPS AIM:

To realize ring counter and Johnson counter using flip flops. COMPONENTS REQUIRED: 1. Digital IC Trainer kit 2. Connecting wires 3. Bread board (If required) 4. IC 7474 – 7474 – 2 2 Nos. THEORY Ring counter A ring counter is a circular shift register with only one flip-flop being set at any particular time; all others are cleared. The single bit is shifted from one flip-flop to the next to produce the sequence of timing signals. Therefore an n-bit ring counter has n-states and requires n D flip-flops to hold the state. Design of 3-bit ring counter The state diagram, state table along with K-map for each D flip-flop input of 3-bit ring counter is shown figure 1.a.

Figure 1.a. State diagram, state table and K-maps for 3-bit ring counter The circuit diagram and truth table of 3-bit ring counter using D flip-flop IC 7474 is shown in figure 1.b.


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Figure.1.b. Circuit Circuit diagram and truth table of ring counter using D flip-flop IC 7474 Johnson counter An n-bit ring counter circulates a single bit among the flip-flops to provide n distinguishable states. Johnson counter is an n-bit switch-tail ring counter with 2n states. The switch-tail ring counter is a circular shift register with the complemented complemented output of the last flip-flop connected connected to the input of the first f irst flip-flop. Design of 3-bit Johnson counter The state diagram, state table along with K-map for each D flip-flop input of 3-bit Johnson counter is shown figure 2.a.

Figure 2.a. State diagram, state table and K-maps for 3-bit Johnson counter The circuit diagram and truth table of 3-bit Johnson counter using D flip-flop IC 7474 is shown in figure 1.b.


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Figure.1.b. Circuit diagram and truth table of Johnson counter using D flip-flop IC 7474 PROCEDURE: 1. Place the ICs on trainer kit. 2. Wire the circuit diagram. 3. Connect VCC and GND to respective pins of trainer kit. 4. Connect the inputs to the input switches provided in the trainer kit. 5. Connect the outputs to the terminals of output LEDs. 6. Apply various combinations combinations of inputs according to the truth table and observe condition of LEDs. RESULTS:

Viva questions: 1. Design a counter with the following state diagram. (2 marks)

2. Design 4-bit ring counter using T flip-flops. (1 marks) 3. Design 4-bit Johnson counter counter using T flip-flops. (1 mark) 4. Identify f/8 counter and draw draw the circuit. (1 mark) Note: Prepare Prepare all ICs ICs pinout diagram diagram and and functions of each pin. pin.


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EXPT. No. 11: FOUR-BIT MAGNITUDE COMPARATOR AIM:

To realize a 4-bit magnitude comparator. COMPONENTS REQUIRED: 1. Digital IC Trainer kit 2. Connecting wires 3. Bread board (If required) 4. IC 7485 – 7485 – 1 1 No. THEORY: The comparison of two numbers is an operation that determines whether one number is greater than, equal to, or less than the other number. Two numbers, A and B can be compared results the followings:     =   0 = 1,     <   1 = 1      >   2 = 1. Where A and B may be any n-bit number. The truth table and circuit diagram of 1-bit magnitude comparator comparator is shown in figure.1.

Figure.1. Truth table and circuit diagram of 1-bit magnitude comparator (Note: Choose appropriate ICs and do the experiment) The pinout diagram, pin functions and truth table of 4-bit magnitude comparator IC 7485 is shown in figure 2.a.


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Figure 2.a. Pinout diagram, pin functions and truth table of 4-bit magnitude comparator IC 7485 The circuit diagram of 4-bit magnitude comparator using IC-7485 is shown in f igure 2.b.

Figure 2.b. 4-bit magnitude comparator comparator using IC-7485 Department of ECE, VKCET

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Observed results:


Viva questions: 1. Draw the circuit diagram diagram of 8-bit magnitude comparator comparator using IC-7485. (3 marks) 2. Design 2-bit comparator comparator using 1x8 demultiplexer. demultiplexer. (2 mark) Note: Prepare Prepare all ICs ICs pinout diagram diagram and and functions of each pins.


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EXPT. No. 12: BCD TO 7-SEGMENT DECODER AND DISPLAY AIM:

To design and realize BCD to 7-segment decoder and display COMPONENTS REQUIRED: 1. Digital IC Trainer kit 2. Connecting wires 3. Bread board (If required) 4. Resistor 180Ω 180Ω – 7 7 No. 5. ICs a) 7447 – 7447 – 1 1 No. b) 7-segment display (Common anode) – anode) – 1 1 No. THEORY BCD to 7-segment decoder is a combinational circuit to convert BCD number to 7-bit binary output. BCD number is binary coded decimal, used to represent decimal number in binary form. Then for one digit BCD number, there will be 4-bit binary number. 7-segment display is LED display, organized by 7 LEDs for displaying all numeric numbers (0 to 9) and few alphabetic characters (A, b, C, d, E, F, H, I, P, t, v). There is also to display dot by 8 th LED. There are two types of 7-segment 7-segment displays: 1) Common anode display – Here the anode terminal of all LEDs are common and input to the display is connected to cathode of each LED. The symbol, internal diagram and pinout diagram of common anode display is shown in figure 1.a. 2) Common cathode display – Here Here the cathode terminal of all LEDs are common and input to the display is connected to anode of each LED. Common anode 7-segment display

Figure 1.a. Symbol, internal diagram and pinout diagram of common anode 7-segment display. Department of ECE, VKCET

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The IC-7447 is 4-bit BCD to 7-segment decoder IC, which convert BCD into corresponding common anode 7-segment signal. The pinout diagram and functions of pins in IC-7447 is shown in figure 1.b.

Figure 1.b. Pinout diagram and functions of pins in IC-7447 The truth table of IC-7447 is shown in figure 1.c.

Figure 1.c. Truth table of IC 7447 The circuit diagram of BCD to 7-segment decoder and display is shown in figure 2.a.


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Figure 2.a. BCD to 7-segment decoder and display. Observation table ( Left side of the record )


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PROCEDURE: 1. Place the ICs on trainer kit. 2. Wire the circuit diagram. 3. Connect VCC and GND to respective pins of trainer kit. 4. Connect the inputs to the input switches provided in the trainer kit. 5. Connect the outputs to the terminals of output LEDs. 6. Apply various combinations combinations of inputs according to the truth table and observe condition of LEDs. RESULT:

Viva questions: 1. Design BCD to decimal decoder decoder (2 marks) 2. Design a 4-bit Gray code to 4-bit binary converter (3 marks) Note: Prepare Prepare all ICs ICs pinout diagram diagram and and functions of each pin. pin.


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EXPT. No. 13: ASTABLE AND MONOSTABLE MULTIVIBRATORS USING ICs AIM:

a) To design astable multivibrator using IC-555. b) To design monostable multivibrator using IC-555. COMPONENTS REQUIRED: 1. Digital IC Trainer kit 2. Connecting wires 3. Bread board (If required) 4. Digital storage oscilloscope / CRO 5. Function generator 6. Resistors 7. Capacitors 8. IC 555 – 555 – 1 1 No. THEORY: Timer IC 555 The Timer IC 555 is a highly stable device for generating accurate time delays or oscillation. The piout diagram diagram and functions functions of pins pins are shown in figure 1.

Figure 1. Pinout diagram and pin functions of IC-555 Astable multivibrator using IC-555 Astable multivibrator is a free running multivibrator or square wave generator. It has no stable state, ie the output switches between ON and OFF states. The circuit diagram for astable multivibrator using IC-555 and the wave forms f orms are shown in figure 2.a and 2.b. respectively. The equation for time period of output wave  = 0.69 0.693 31 + 22 , where ON period 1 = 0.69 0.693 31 + 2  and OFF period 2 = 0.69 0.693 32 . The duty cycle of output wave form

=

1 +2 1 +22

× 100% 100% .


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Figure 2.a. Astable Multivibrator using IC-555

Figure 2.b. Model wave forms Design: For f = 1kHz and D=75%, T = 1ms, T1 = D x T = 0.75 x 1ms = 0.75ms, T2 = T – T – T T1 = 0.25ms We have  =

1 +2 1 +22

× 100% 100% ,

1 +2 1 +22

= 0.75 0.75,,

From 2 = 0.69 0.693 32 , choose C = 0.1µF, 2 =

1

= 2.

2 2

0.693

= 3.6Ω.

Then R 1 = 2R 2 = 7.2kΩ (Use 6.8kΩ std. value) Observed waveforms: (on left page) (Draw the wave at Vo and Vc with time periods) Monostable multivibrator using IC-555 The monostable multivibrator is a one-shot multivibrator, in which the duration of the output pulse is determined by the RC circuit connected externally to the 555 timer. It has one stable state and one unstable state. For applying a trigger to the circuit, it goes to its unstable state from its stable state. After the time determined by RC circuit, it comes back to its stable state from the unstable state. The circuit diagram for monostable multivibrator using IC-555 and the wave forms are shown in figure 3.a. and 3.b. respectively. Department of ECE, VKCET

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The equation for the time period of unstable state is  = 1.1

Figure 3.a. Monostable multivibrator using IC-555

Figure 3.b. Model wave forms Design For T = 5ms, choose C = 0.1µF. We have  = 1.1, then R = 45kΩ (Use std. value 43kΩ) Note: For trigger in, choose choose t 1 < T and T t t > T. Then for given T = 5ms, choose t 1 = 1ms and T t t = 9ms, then frequency of trigger pulse is 1/10ms =100Hz, with duty cycle 90%

Observed waveforms: (On (On left page) (Draw the wave at Trigger in, Vo and Vc with time periods)


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Digital System Design Lab Manual (08.408 Btech Cse Kerala University)

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