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4. Design a 4 bit universal shift register using MUXs and DFFs which can do the following operations:

a) Right shift. b) Left shift c) Circular right shift d) Circular left shift

5. Design a synchronous counter which goes through the following sequence of states using D flip-flops.

11 10 01 00 11 10 01 00

6. Design a synchronous 3-bit Up/Down counter having Gray code sequence. 7. Construct a Johnson counter for ten timing signals. 8. You are asked to build a digital lock which opens ONLY with the combination 0111.

Design a synchronous digital system that the electronic system of this lock would comprise, using:

a) D flip-flops b) J-K flip-flops

Which implementation requires lesser combinational logic? What are the advantages of using each type of flip-flop? Which flip-flop, in your opinion, would be used more (generally) in real-life for such design and why? (Note: Assume that the stream of bits at the input is read-in MSB first, i.e., 0 comes first here.)

9. An AB latch operates as follows: If A = 0 and B = 0, the latch state is Q = 0; if either A = 1 or B = 1 (but not both), the latch output does not change; and when both A = 1 and B = 1, the latch state is Q = 1.

a) Construct the state table and derive the characteristic equation for this AB latch. b) Derive a circuit for the AB latch that has four two-input NAND gates and two

inverters. c) In your circuit of Part (b), are there any transitions between input combinations

that might cause unreliable operation? Verify your answer. d) In your circuit of Part (b), is there a gate output that provides the signal Q?

Verify your answer. 10. A latch can be constructed from an OR gate, an AND gate, and an inverter connected as

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