How can we implement a conditional statement using basic logic gates? To answer this question, I will 1
introduce you to the multiplexer concept as the building block of the decision making process in hardware. 2
A multiplexer is one of the basic concepts in logic circuits. 3
It is a digital switch in which the output o is either a or b, depending on the value of s. 4
If s is 0 then o is the same as a. And if s is 1 then o is the same as b. The multiplexer 5
has two types of inputs: Data inputs which determine the different options of the output, 6
Select or control inputs which choose one of the inputs to be connected to the output. 7
A generalised multiplexer can have n data inputs, m select inputs and one output. A value on the 8
select input connects one of the data inputs to the output. In order to have a practical circuit, 9
the number of data inputs should be less or equal than 2 to the mth power. 10
A multiplexer can be implemented by basic logic gates. This design is a typical implementation 11
of a 2x1 multiplexer using AND, OR and NOT gates. 12
When the s is 0 then a propagates to the output And when s is 1 b propagates to the output. 13
After getting familiar with the concept of the multiplexer. The question is: What is the generalised 14
form of a multiplexer in a real design? In the next lecture, 15
I will answer this question. 16
These are the takeaway messages. Multiplexer is the primary building block in implementing a decision-making 17
process in hardware. 18
A multiplexer has two groups of inputs, including data and select, and an output. 19
Now the quiz question. How can a group of basic logic gates implement this 4x1 multiplexer?