lecture 8

The encoder
The encoder is a combinatory logic circuit which outputs an exclusive binary code when
each of its inputs is activated. When one of its inputs is activated, a binary code
corresponding to that input is sent to the output. The encoder does the reverse of the
decoder. Encoder circuits are used in the conception of keyboards

Let us realise an 8 to 3 encoder. It is a combinatory logic circuit having 8 inputs
and 3 outputs which functions in such a way that, when an input is activated, a
corresponding binary number coded in three bits is sent to the output.

encoder with priority
The encoder designed above would produce a wrong result if two inputs were
activated at the same time. There are encoders with priority circuits which functions in
such a way that, if two or more inputs are activated at once, the binary code sent to the
output is that of the input having the highest value. For instance, if the inputs I2, I5 and
I6 are activated the same time, the encoder will output the binary code 110
corresponding to the input I6.