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Cadenti
logic family
medium scale integration
metal oxide semiconductor
ac register
accumulator logic
adder circuit
basic computer design
branch unconditionally
flowchart
input and output communication
input output instruction
input register
interrupt cycle
logic adder circuits
logic gates
output register
register and memory
binary code
binary number
clock pulse
data types
decimal numbers
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State Diagram
The information available in a state table can be represented graphically in a state diagram state diagram. In this type of diagram, a state is represented by a circle, and the transition between states is indicated by directed lines connecting the circles. The state diagram of the sequential circuit of Fig. 1-25 is shown in Fig. 1-26. The state diagram provides the same information as the state table and is obtained directly from Table 1-4. The binary number inside each circle identifies 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 number after the slash gives the output during the present state. For example, the directed line from state 00 to 01 is labeled 1/0, meaning that when the sequential circuit is in the present state 00 and the input is 1, the output is 0. After a clock transition, the circuit goes to the next state 01. The same clock transition may change the input value. If the input changes to 0, the output becomes 1, but if the input remains at 1, the output stays at 0. This information is obtained from the state diagram along the two directed lines emanating from the circle representing state 01. A directed line connecting a circle with itself indicates that no change of state occurs.
Figure 1-25
Figure 1-26
There is no difference between a state table and a state diagram except in the manner of representation. The state table is easier to derive from a given logic diagram and the state diagram follows directly from the state table. The state diagram gives a pictorial view of state transitions and is the form suitable for human interpretation of the circuit operation. For example, the state diagram of Fig. 1-26 clearly shows that starting from state 00, the output is 0 as long as the input stays at 1. The first 0 input after a string of 1's gives an output of 1 and transfers the circuit back to the initial state 00.
Table 1-4
