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## Description

Objective:

In this experiment, you will use Logisim to analyse and design sequential circuits.

Part I

1. Run Logisim, open the file lab10part1.circ. The circuit is shown below. 1. The circuit consists of two JK flip-flop and an OR gate. Note the following:

• The outputs of the two JK flip-flops are labelled A and B, which form the state of the circuit.

• The Clock is connected to the clock inputs of the flip-flops.

• The logic constant 1 is connected to the Enable inputs of the flip-flops.

• The Clear switch is connected to the clear inputs of the flip-flops. Hence when Clear = 1, it clears the contents of both flip-flips to 0, bringing the circuit to the initial state of AB=00.

• The flip-flop inputs are as follows:

AY2019/20 Semester 2 – 1 of 3 – CS2100 Lab #10

 For flip-flop A: JA=A+B; KA=0 For flip-flop B: JB=1; KB=A+B 3. Complete the following table: [6 marks] Present state Flip-flop inputs Next state A B JA KA JB KB A+ B+ 0 0 0 1 1 0 1 1
1. Verify the correctness of your table above by testing the circuit in Logisim.

1. Click on “Clear” input to get 1. This clears both flip-flops to 0, bringing the circuit to the initial state of AB=00.

1. Click on “Clear” input to get 0 before you proceed. This puts the flip-flops in their normal operation mode.

1. Clicking the “Clock” input toggles its value. When the “Clock” value changes from 0 to 1 (i.e. a rising edge), the flip-flops react according to the commands at their J and K inputs.

1. Click the “Clock” input several times to simulate the square wave, and watch the outputs of the flip-flops change their values. Do the values follow your table above?

1. If at any point of time you want to reset the flip-flops to the initial state of 00, go to step (a) above.

5. Complete the state diagram below. [4 marks] 00  01 10 11

AY2019/20 Semester 2 – 2 of 3 – CS2100 Lab #10

Part II

1. You will design a sequential circuit using JK flip-flops. The flip-flop inputs are given below:

 For flip-flop A: JA=1; KA=A B For flip-flop B: JB=0; KB = (A B)’ 7. Complete the following table: [6 marks] Present state Flip-flop inputs Next state A B JA KA JB KB A+ B+ 0 0 0 1 1 0 1 1
 8. Complete the state diagram below. [4 marks] 00 01 10 11    9. Implement the circuit on Logisim and save it under lab10part2.circ and send it to your lab TA along with the completed lab report. In your circuit, you should also include a “Preset”

input so that you can set both flip-flops to 1. [5 marks]

10. As this is your final lab, your lab report will not be returned to you.

Total: 25 marks

AY2019/20 Semester 2 – 3 of 3 – CS2100 Lab #10