Mallard ECE 290: Computer Engineering I  Spring 2007  Graded Web...
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Graded WebQuiz : Basic Encoders
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Simple Encoders
An
encoder
is a combinational network for which exactly one input line is a 1; the output gives the
binary representation of that input. In other words, the encoder gives the "encoding" of that input line
which is 1.
4to2 Binary Encoder
A simple example is a 4to2 binary encoder, as shown below. There are 4 input lines D0, D1, D2, and
D3.
If input line D2 is a 1, then the output gives the binary encoding of "2", which is A1A0 = 10.
If input line D0 is a 1, then the output is A1A0 = 00.
If input line D1 or D3 is a 1  you complete the table below with the correct output values!
4to2 Binary Encoder
D3
D2
D1
D0
A1
A0
0
0
0
1
0
0
0
0
1
0
0
1
0
1
0
0
1
0
1
0
0
0
1
1
Implementation of the 4to2 Encoder
Having completed the above truth table, the implementation is easy: we give boolean expressions for A1
and for A0:
A1 = D3 + D2
A0 = D3 + D1
Hence, the circuitry inside this encoder would consist simply of two OR gates.
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 Spring '08
 Staff
 Boolean Algebra, input line, priority encoder, BINARY ENCODER, Mallard ECE

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