Page 42 - CITS - Electronic Mechanic - TT - 2024
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ELECTRONICS MECHANIC - CITS



           Encoder
           •   It is a combinational circuit.
           •   It has ‘n’ input lines & ‘m’ output lines.

           •  An encoder produces an ‘m’ bit binary code corresponding to the digital input number of ‘n’bits.
           •  Many types of Encoders – Octal to Binary (8 to 3), Decimal to BCD (10 to 4)etc.
           •  The block diagram is as shown below,
















           Priority Encoder
           •  This is special type of encoder.

           •  Priorities are given to the input lines.
           •  Iftwoormoreinputlinesare‘1’at the same time, then the input line with highest priority will be considered.
           •  The block diagram is shown below















           •  The truth table of priority encoder is as given below,
           •  There are four inputs, D0 through D3 and outputs Y1 and Y0. Out of the four inputs D3 has the highest priority
              and D0 has the lowest priority.

           •  That means if D3 = 1 then Y1Y0 = 11 irrespective of the other inputs. Similarly if D3 = 0 and D2 = 1 then Y1Y0
              = 10 irrespective of other inputs
                                                       Truth Table

                                           Inputs                                 Outputs
                           D 3         D 2         D 1         D 0           Y 1            Y 0
                           0           0           0           0             X               X
                           0           0           0           1             0               0
                           0           0           1           X             0               1
                           0           1           X           X             1               0
                           1           X           X           X             1               1









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                                    CITS : E & H - Electronics Mechanic - Lesson 9 - 29
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