CONTENTS Sl. No. Experiment Page No

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1 CONTENTS Sl. No. Experiment Page No 1a Given a 4-variable logic expression, simplify it using Entered Variable Map and realize the simplified logic expression using 8:1 multiplexer IC. 2a 3a 4a 5a 6a 1b 2b 3b 4b Realize a J-K Master / Slave Flip-Flop using NAND gates and verify its truth table. Design and implement a mod-n (n<8) synchronous up counter using J-K Flip-Flop ICs and demonstrate its working. Design and implement a ring counter using 4-bit shift register and demonstrate its working. Design and implement an asynchronous counter using decade counter IC to count up from 0 to n (n<=9) and demonstrate its working. Design and construct a 4-bit R-2R ladder D/A converter using Op- Amp. Determine its accuracy and resolution. Design and develop the Verilog /VHDL code for an 8:1 multiplexer. Simulate and verify its working. Design and develop the Verilog / VHDL code for D Flip-Flop with positive-edge triggering. Simulate and verify its working. Design and develop the Verilog / VHDL code for mod-8 up counter. Simulate and verify its working. Design and develop the Verilog / VHDL code for switched tail counter. Simulate and verify its working. Mohan H G, Assistant Professor Page 1

2 List of IC Numbers IC Number NAND Gate (2-input) 7400 NOR Gate (2-input) 7402 NOT Gate 7404 AND Gate (2-input) 7408 NAND Gate ( 3-input) 7410 AND Gate (3-input) 7411 OR Gate (3-input) 7432 Multiplexer Shift Register 7495 Decade Counter 7490 Mohan H G, Assistant Professor Page 2

3 1a Given a 4-variable logic expression, simplify it using Entered Variable Map and realize the simplified logic expression using 8:1 multiplexer IC. Aim : To simplify a given 4-variable logic expression using EVM and realize it using a 8:1 Multiplexer IC. Components : Sl. No. Particulars Specification Quantity 1 Multiplexer IC NOT Gate Trainer Kit Patch Cords - 20 Background: Multiplexer means many into one. It is a circuit with many inputs but only one output. By applying control signals, it can steer any input to the output. The number of inputs to a multiplexer is multiple of 2 (2, 4, 8, 16, ) but the number of output is always one. Hence, it is also called as data selector and control inputs are termed as select inputs. The circuit has n input signals, m control signals and 1 output signal. m control signals can select at the most 2 m input signals, thus n <= 2 m. Multiplexer is sometimes called as universal logic circuit because a 2 n to 1 multiplexer can be used as a design solution for any n variable truth table. In Entered Variable Map, one of the input variable is placed inside the Karnaugh Map, this variable is called as Map Entered Variable (MEV). The method records how this variable is related to the output. Hence, the method reduces K-map size by one degree. For instance, a 4 variable problem has 2 4 = 16 locations in K-map, using EVM method it can be reduced to = 2 3 = 8 locations in EVM. Mohan H G, Assistant Professor Page 3

Function Table : Inputs Outputs A B C EN Q Q X X X 1 1 1 0 0 0 0 D0 D0 0 0 1 0 D1 D1 0 1 0 0 D2 D2 0 1 1 0 D3 D3 1 0 0 0 D4 D4 1 0 1 0 D5 D5 1 1 0 0 D6 D6 1 1 1 0 D7 D7 Observation If EN pin is at

4 Function Table : Inputs Outputs A B C EN Q Q X X X D0 D D1 D D2 D D3 D D4 D D5 D D6 D D7 D7 Observation If EN pin is at logical high value then irrespective of the input values, the output will be 1. If EN pin is at logical zero value and the input is then the output will be D0 If EN pin is at logical zero value and the input is then the output will be D1 If EN pin is at logical zero value and the input is then the output will be D2 If EN pin is at logical zero value and the input is then the output will be D3 If EN pin is at logical zero value and the input is then the output will be D4 If EN pin is at logical zero value and the input is then the output will be D5 If EN pin is at logical zero value and the input is then the output will be D6 If EN pin is at logical zero value and the input is then the output will be D7 Mohan H G, Assistant Professor Page 4

5 EVM Method : The method works as follows Let s consider A, B and C variables to be fed as select inputs and fourth variable D to be present as data input using Entered Variable Map method. All combinations of 3 select inputs and the data input is written in the truth table. Corresponding Q value (the output) is written using the given logic expression. Observe how the MEV variable D is related to the output and make the corresponding entries in the MEV map. Don t care (X) values can be treated as either 1 or 0. For the 8 combinations of control inputs, the corresponding 8 inputs for the MUX is noted. Using these 8 inputs, the 8:1 MUX circuit can be designed and implemented. Entry in MEV Map for all possible values of MEV (D) and Output (Q) MEV Output Entry in MEV Output Entry in D Q MEV Map D Q MEV Map X X D X X D X X 0 1 X 0 X X X Mohan H G, Assistant Professor Page 5

6 Input: A 4 variable logic Expression, f (A,B,C,D) = (2,4,5,7,10,11,14) + d(8,9,12,13,15) Decimal Value Inputs MEV Output A B C D Q X X X X X Entry in MEV Map D0 = D. 0 + D. 0 = 0 D1 = D. 1 + D. 0 = D D2 = D. 1 + D. 1 = 1 D3 = D. 0 + D. 1 = D D4 = D. X + D. X = X D5 = D. 1 + D. 1 = 1 D6 = D. X + D. X = X D7 = D. 1 + D. X = 1 Procedure : 1. Verify all the components and patch cords for their good working condition. 2. Connect A, B, C, D to the input ports and Q to the output port of the trainer kit. 3. Don t care (X) entries in the EVM can be connected to either Ground or Vcc. 4. Use IC 7404 to get D, connect pin 14 to Vcc, pin 7 to Ground and input D to pin Connect IC pins to pin 2 of IC 7404 where ever D is required. 6. Make the connection as shown in the circuit diagram. 7. Give the power supply to the trainer kit. Mohan H G, Assistant Professor Page 6

7 8. Provide the input data to circuit via trainer kit switches (A, B, C and D) and verify the Circuit : truth table. Mohan H G, Assistant Professor Page 7

8 4a Design and implement a ring counter using 4-bit shift register and demonstrate its working. Aim : To design a ring counter using 4-bit shift register. Components : Sl. No. Particulars Specification Quantity 1 Shift Register IC Trainer Kit Patch Cords - 20 Background: A shift register is a cascade of flip flops, sharing the same clock, in which the output of each flip-flop is connected to the data input of the next flip-flop in the chain. The circuit shifts the bit array stored in it by one position. Shifting of data takes place at each transition of the clock input. A ring counter is a counter, where the output of one flip-flop connects directly into the input of another to produce a particular output pattern. The ability to load the flip-flops to particular state permits a repeatable output pattern. There are two types of ring counters: A straight ring counter (Overbeck counter) connects the output of the last shift register to the first shift register input and circulates a single one (or zero) bit around the ring. For example, in a 4-bit register, with initial register values of 1000, the repeating pattern is: 1000, 0100, 0010, 0001, A twisted ring counter (Johnson counter) connects the complement of the output of the last shift register to the input of the first register and circulates a stream of ones followed by zeros around the ring. Mohan H G, Assistant Professor Page 8

9 For example, in a 4-bit register counter, with initial register values of 0000, the repeating pattern is: 0000, 1000, 1100, 1110, 1111, 0111, 0011, 0001, IC 7495: Circuit for Ring Counter : The Pins A, B, C and D are used to load the flip flops with required values. QA, QB, QC and QD are outputs of individual flip flops. The output of last flip flop (QD) is fed as input to the first flip flop through pin 1. Pin 1 is input to the first flip flop. The state table is shown for the pattern Procedure : 1. Verify all the components and patch cords for their good working condition. 2. Make connection as shown in the circuit diagram. 3. Connect pin 7 of 7495 IC to GND and pin 14 to V CC. Mohan H G, Assistant Professor Page 9

10 4. Connect A, B, C, D and MODE (pin 2, 3, 4, 5, 6) to the input ports of the trainer kit. 5. Connect QA, QB, QC and QD (pin 13, 12, 11, 10) to the output ports of the trainer kit. 6. Provide feedback by connecting pin 10 to pin Short pin 8 and pin 9 to clock pulse, use MonoPulse or 1 Hz TTL. 8. Give supply to the trainer kit. 9. Select the pattern for ring counter by setting the input pins A, B, C, D to the required pattern. For example to load 1000 value. Set A, B, C and D input values to 1, 0, 0 and 0 respectively. 10. To load the 4-bit input to the ring counter set the MODE pin 6 to 1. When MODE pin is set to 1 the pattern is loaded to respective flip flops parallely in a single clock cycle. 11. After loading the pattern, set the mode pin 6 to 0 inorder to start the ring counter operation. Apply clock pulses to check the working. Observe the right shifting of data on each clock pulse. 12. If clock pin 8 and 9 are connected to MonoPulse then keep pressing the clock pulse till the original pattern repeats. If clock pin 8 and 9 are connected to TTL then clock pulses are applied automatically. 13. Give different patterns of inputs and verify the working of ring counter. Workout: Johnson Counter (Switched Tail Counter) : Mohan H G, Assistant Professor Page 10

11 5a Design and implement an asynchronous counter using decade counter IC to count up from 0 to n (n<=9) and demonstrate its working. Aim : To design an asynchronous counter for a given modulo n. Components : Sl. No. Particulars Specification Quantity 1 Decade Counter IC input - AND Gate Trainer Kit Patch Cords - 20 Background: A counter is a register that goes through a predetermined sequence of states upon the application of input pulses. In asynchronous counter a clock signal is provided for one flip-flop and its output is provided as clock source for next flip-flop. The output of asynchronous counter is not synchronized with clock signal. A decade counter follows a sequence of 10 states and returns to zero after the count of nine. Such a counter must have atleast 4 flip flops to represent each decimal digit, since a decimal digit is represented by a binary code with atleast 4 bits. IC 7490: The 74LS90 is a simple counter, it can count from 0 to 9 cyclically in its natural mode. It counts the input pulses and the output is received as a 4-bit binary number through pins Q A, Q B, Q C and Q D. The binary output is reset to 0000 at every tenth pulse and count starts from 0 again. A pulse is also generated (at pin 9) as it resets its output to The chip can count up to other maximum numbers and return to zero by changing the modes of These modes are set by changing the connection of reset pins R 1 - R 4. For example, if either R 1 & R 2 are high or R 3 & R 4 are ground, then it will reset Q A, Q B, Mohan H G, Assistant Professor Page 11

12 Q C and Q D to 0. If resets R 3 & R 4 are high, then the count on Q A, Q B, Q C and Q D goes to Function Table: Input Output R1 R2 R3 R4 QD QC QB QA H H L X H H X L L X H H X L H H L X L X COUNT X L X L COUNT L X X L COUNT X L L X COUNT It can be noted that the outputs will be set to 0000 whenever R1and R2 are high. And the outputs will be set to 1001 whenever R3and R4 are high. All four R1, R2, R3 and R4 cannot be high at the same time. In all other cases, the outputs will follow the counter. State Diagram: Mohan H G, Assistant Professor Page 12

13 Working : 1. Connect power supply V CC to pin 5 and GND to pin 10 of IC Connect pin 14 to mono pulse or TTL (1KHz) and output pins are QA (pin 12), QB (pin 9), QC (pin 8) and QD (pin 11) to the output port of trainer kit. 3. Note that QD is MSB pin followed by QC, QB, QA. QD must be leftmost output and QA is rightmost output. 4. Reset pins R1, R2, R3 and R4 are connect to GND, i.e pin 2, pin 3, pin 6 and pin 7 to GND. 5. Apply clock pulse using mono-pulse or TTL, the counter starts counting from 0 to 9 repeatedly. This verifies the working of decade counter. Designing Mod 5 Counter : Mod 5 counter must count from 0 to 4, which means when the output becomes 0101, it must be reset to 0. The counter can be reset to 0 by making R1 and R2 values as 1 (High). Observe the number 0101, where QD = 0, QC = 1, QB = 0 and QA = 1. Consider only those output values which are high. In this case QC and QA are high. Thus, counter must be reset to 0 when ever QC and QA are high. Provide QC and QA as input to the AND Gate, and connect the output of AND Gate to R1 and R2. When ever QC and QA are high, the output of AND Gate will be high, since AND Gate output is connected to R1 and R2, the counter will be reset to 0. Mohan H G, Assistant Professor Page 13

14 Circuit for Mod 5 Counter Designing Mod 7 Counter : Mod 7 counter must count from 0 to 6, which means when the output becomes 0111, it must be reset to 0. Where QD = 0, QC = 1, QB = 1 and QA = 1. Counter must be reset to 0 when ever QC, QB and QA are high. Perform AND operation of QC, QB and QA and connect the output of AND operation to R1 and R2. The AND operation od QC, QB and QA can be done as shown in the circuit. When ever QC, QB and QA are high, the output of AND Operation will be high, since the output is connected to R1 and R2, the counter will be reset to 0. Circuit for Mod 7 Counter Mohan H G, Assistant Professor Page 14

15 Designing Mod 4 Counter : Mod 4 counter must count from 0 to 3, which means when the output becomes 0100, it must be reset to 0. Where QD = 0, QC = 1, QB = 0 and QA = 0. The counter must be reset to 0 when ever QC is high. Hence, directly connect QC to R1 and R2. Circuit for Mod 4 Counter Designing Other Modulo s: Mod 2 counter can be obtained by directly connecting QB to R1 and R2. Mod 3 counter can be obtained by connecting AND operation output of QA and QB to R1 and R2. Mod 6 counter can be obtained by connecting AND operation output of QB and QC to R1 and R2. Mod 8 counter can be obtained by directly connecting QD to R1 and R2. Mohan H G, Assistant Professor Page 15

16 6a Design and construct a 4-bit R-2R ladder D/A converter using Op-Amp. Determine its accuracy and resolution. Aim : To design a D/A converter using μa 741 IC and find its accuracy and resolution. Components : Sl. No. Particulars Specification Quantity 1 Op-Amp μa Resistors 1 KΩ, 2.2 KΩ 4, 6 3 Trainer Kit Bread Board Volt Meter Connecting Wires - 20 Background: Digital to analog converter (DAC) is used to get analog voltage corresponding to an input digital data. Data in binary digital form can be converted to corresponding analog form by using a R-2R ladder (binary weighted resistor) network and a summing amplifier. A digital to analog converter accepts an n-bit input word in binary and produces an analog signal proportion to it. There are mainly two techniques used for analog to digital conversion. 1. Binary weighted resistor D/A converter 2. R/2R ladder D/A converter In these techniques the shunt resistors are used to generate n binary weighted currents. These currents are added according to switch positions controlled by the digital input and then converted into voltage to get analog voltage equivalent to digital input. R/2R ladder uses only two resistor values. This avoids resistance spread drawback. Mohan H G, Assistant Professor Page 16

Fan in: The number of inputs of a logic gate can handle.

Fan in: The number of inputs of a logic gate can handle. Subject Code: 17333 Model Answer Page 1/ 29 Important Instructions to examiners: 1) The answers should be examined by key words and not as word-to-word as given in the model answer scheme. 2) The model