lecture 9

The multiplexer:
A multiplexer also called data selector is a combinatory logic circuit which permits to
direct towards single output information coming from many inputs. According to the
address received by the multiplexer, only one among the information available at its
inputs is selected and directed toward the output. A multiplexer can be considered as
a commutator having multiple poles which are switched according to the address sent
to the multiplexer.

E is the enable input. It enables the multiplexer to function when the right logic signal
level is sent to it (For the principle diagram above, the right signal level is slow). For an
address bus having n lines, up to 2n data can be addressed such that for each of these
addresses, one among the 2n data is selected and directed towards the output.
Let us design an elementary multiplexer. It is a multiplexer having two data
inputs I0 and I1 and one address input A

The address can be either 0 or 1. When the address is 0, the datum I0is selected
and sent to the output. When the address is 1, I1 is selected and directed towards the
output.