Post on 16-Jan-2022
transcript
Example) sequence detector
Functional specification: Detects three or more consecutive 1’s in a string of bits coming through an input line
1) state diagram
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synthesis using D flip-flops
2) assign binary codes to the states and obtain resulting state table
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3) Choose two D type flip-flop, label them as A and B, one input x, one output y.
)7,6(),,(
)7,5,1(),,()1(
)7,5,3(),,()1(
xBAy
xBADtB
xBADtA
B
A
input equations
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Excitation table
Design with other than D flip-flop input equations must be derived indirectly from the state table
Need a table that lists the required inputs for a given change of state excitation table
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use the excitation table for JK flip-flop to determine the flip-flop input derive the truth table for the combinational circuit (input=present state+external inputs, output=flip-flop inputs+external output) derive the flip-flop function from the truth table (apply the map) draw the logic diagram
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synthesis using T flip-flops
counter : a sequential circuit that goes through a prescribed sequence of states upon the input pulse input pulse may be clock pulse or an external input binary counter : counter that follows the binary sequence
-No input, no output -Use T flip-flop
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