ECE 103
DIGITAL LOGIC DESIGN
CHAPTER V
SEQUENTIAL LOGIC
CIRCUITS
PART 2
Reference: M. Morris Mano & Michael D. Ciletti, "Digital Design", Fourth
Edition, Prentice Hall of India Pvt. Ltd., Chapter – Chapter -5 & 6
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Excitation Table For a T Flip Flop
Row
Q
Q+
T
Previous State -> Present
State
T
0
0
0
0
0 -> 0
0
1
0
1
1
0 -> 1
1
2
1
0
1
1 -> 0
1
1 -> 1
0
3
1
1
0
Excitation Table For a JK Flip Flop ("X" is "don't care")
Previous State ->
Present State
J
K
0 -> 0
0
X
0 -> 1
1
X
1 -> 0
X
1
1 -> 1
X
0
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Assignments Problems
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Assignments Problems…
 The contents of a 4-bit register is initially 0000. The register is
shifted eight times to the left, with the sequence 00101011 as the
serial input. The leftmost bit of the sequence is applied first. What is
the content of the register after each shift?
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Assignments Problems…
 Design a finite state machine to detect a bit pattern in a sequence of
binary bits. The FSM will have one data input X, a reset input R, and
an output Y. Y is ‘1’ when the previous four bits received have the
pattern “0110” and ‘0’ otherwise. In the example below the pattern
occurs twice, and Y=’1’ on the following clock cycle.
 X = 011101101001110110001
 Y = 000000001000000000100
 a. Determine how many states are required, and make a state
transition table.
 b. Determine the number of D flip‐flops and find the Boolean
equations for the next‐state logic and the output logic.
 c. Sketch a schematic of your design.
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Assignments Problems…
 Suppose a certain sequential circuit has a JK flip-flop labeled A and
a D flip-flop labeled B. In
 addition, the circuit has an input x and an output y. The formulas for
the flip-flop inputs and y
 are given below.
 JA = x0
 KA = B0
 DB = A0 + B00
 y = xA0B0
 (a) Draw the circuit.
 (b) Write the next state equation for the A flip-flop.
 (c) Write the next state equation for the B flip-flop.
 (d) Write down the state table of the circuit.
 (e) Write down the state diagram of the circuit.
 For the circuit in Figure 1, write down the next state equation for the
A flip-flop
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Assignments Problems…
 For the circuit in Figure 2, do the following:
(a) Write the next state equation for the A flip-flop.
(b) Write the next state equation for the B flip-flop.
(c) Write down the output equation for y.
(d) Write down the state table of the circuit.
(e) Write down the state diagram of the circuit.
 For the circuit in Figure 3, do the following:
(a) Write the next state equation for the A flip-flop.
(b) Write the next state equation for the B flip-flop.
(c) Write down the output equation for y.
(d) Write down the state table of the circuit.
(e) Write down the state diagram of the circuit.
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Assignments Problems…
For more problems :
Refer : M. Morris Mano, "Digital Design",
3rd Edition, Prentice Hall of India Pvt.
Ltd., Chapter Pages()
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Assignments Problems…
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Assignments Problems…
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Assignments Problems…
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Assignments Problems…
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Assignments Problems…
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