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1
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the circuit detects that two 4-bit binary codes (say, X and Y) are equal.
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| 2
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corresponding bits, such as bit 0 of code X and bit 0 of code Y, are connected to the two input pins of the first exclusive-or gate. bit 1 of code X and bit 1 of code Y are connected to the next exclusive-or gate, etc.
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| 3
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the output of the exclusive-or gate is logic "1" if the corresponding bits are the same.
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| 4
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these outputs are compared by "or" gates, which give a final output of logic "0" if all the corresponding bits of codes X and Y are equal.
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| 5
|
555
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