Page 119 - Handout Digital Electronics
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15.2 The Sequential State Diagram
Information in a state table can be represented graphically in a state diagram. In a state diagram a circle
represents a state and the transition between states is indicated by directed lines connecting the circles.
The binary number inside the circle represents the state of the flip flops. The directed lines are labeled
with two binary numbers separated by a slash. The input value during the present state is labeled first
and the binary number after the slash gives the output. A directed line connecting a circle with itself
means that no change of state occurs.
0/0
00
0/1 10 1/0
0/1
1/0
0/1 0/1 1/0
01
0/1 1/0
Figure 52: Sequential circuit state diagram 11
15.3 Full design of a sequential circuit
The design procedure of a sequential circuit consists of the following steps:
• Translating the circuit specifications into a state diagram.
• Converting the state diagram into a state table (excitation table)
• From the excitation table obtain the logic equations of the circuit diagram.
Example: Design a clocked sequential circuit that goes through a sequence of repeated binary States 00,
01, 10, 11, 00, 01, etc. when an external input x is equal to 1. The state of the sequential circuit remains
unchanged when the external input x = 0.Produce its state table showing how it functions.
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