Assignment No. 7 – Sequential Circuit Design

1.    A sequential circuit with two D flip-flops A and B, two inputs X and Y, and one output Z is specified by the following input equations:   a.    Draw the logic diagram of the circuit.

b.    Derive the state table.

c.    Derive the state diagram.

2.    The sequential circuit shown below has two D flip-flops, one input X, and one output Y. Derive the state table and state diagram of the circuit. 3.    Design a sequential circuit with two D flip-flops A and B and one input X.  When X = 0, the state of the circuit remains the same.  When X = 1, the circuit goes through the state transitions from 00 to 10 to 11 to 01, back to 00, and then repeats.

4.    A Universal Serial Bus (USB) communication link requires a circuit that produces the sequence 00000001.  You are to design a synchronous sequential circuit that starts producing this sequence for input E = 1.  Once the sequence starts, it completes.  If E = 1, during the last output in the sequence, the sequence repeats.  Otherwise, if E = 0, the output remains constant at 1.

a.    Draw the Moore state diagram for the circuit.

b.    Find the state table and make a state assignment.

c.    Design the circuit using D flip=flops and logic gates.  An asynchronous set or reset should be included to place the circuit in the appropriate initial state at which E is examined to determine if the sequence of constant 1s is to be produced.