This document discusses encoders, which are combinational logic circuits that take binary input and produce a binary output code. It provides examples of an 8-to-3 binary encoder and how it works, showing that an encoder activates a unique 3-bit output code depending on which single input is activated. The document also gives exercises for readers to design encoders and convert decimal numbers to binary-coded decimal.

2. Keyboard

3. THE COMBINATIONAL LOGIC
CIRCUITS
ENCODER

4. Some information about the
Encoder:
# An encoder has a number of input lines, only one
of which input is activated at a given time and
produces an N-bit output code, depending on
which input is activated.
# An encoder is a combinational logic circuit that
essentially performs a “reverse” of decoder
functions.
# Encoders can also be devised to encode
various symbols and alphabetic Letters.

5. Inputs Outputs
I 0 I 1 I 2 I 3 I 4 I 5 I 6 I 7 y2 y1 y0
1 0 0 0 0 0 0 0 0 0 0
0 1 0 0 0 0 0 0 0 0 1
0 0 1 0 0 0 0 0 0 1 0
0 0 0 1 0 0 0 0 0 1 1
0 0 0
0
0 1 0 0 0 1 0 0
0 0 0 0 1 0 0 1 0 1
0 0 0 0 0 0 1 0 1 1 0
0 0 0 0 0 0 1 1 1 1
I0
I1
I2
I3
I4
I5
I6
I7
y2 = I4 + I5 + I6 + I7
y1 = I2 + I3 + I6 + I7
y0 = I1 + I3 + I5 + I7
0
8-to-3 Binary
Encoder
At any one time, only
one input line has a value
of 1.
y2
y1
y0

6. Example (1):
Design IC consists of 3 bits and draw its truth table
with make clear each output what is equal .

7. Example (2):
How many number of outputs if we have 8 inputs ,
make clear with draw and truth table

8. Exercise:
Show how the decimal –to-BCD encoder
converts the decimal number 3 into a BCD 1100.

9. The correct solution:

10. Experiment ( Group
work) :