A multiplexer (MUX) is a digital device that is used to select one of several input data sources and route it to a single output line. It operates based on the control inputs that determine which data source to choose. Multiplexers are commonly used in digital circuits, microprocessors, communication systems, and other applications where data selection is required.
The basic operation of a multiplexer can be understood using a simple analogy: think of it as a "data traffic controller" that directs data from different sources to a single destination. Let's explore the operation of a 4-to-1 multiplexer as an example:
A 4-to-1 multiplexer has four input lines (usually labeled D0, D1, D2, and D3), one output line (labeled Y), and two control inputs (often labeled S0 and S1). The control inputs determine which input data line will be connected to the output line. The number of control inputs (in this case, 2) determines the number of input lines a multiplexer can handle (in this case, 2^2 = 4 input lines).
Here's the truth table for a 4-to-1 multiplexer:
S1 S0 Output (Y)
0 0 D0
0 1 D1
1 0 D2
1 1 D3
When S1=0 and S0=0, the output Y will be connected to input D0.
When S1=0 and S0=1, the output Y will be connected to input D1.
When S1=1 and S0=0, the output Y will be connected to input D2.
When S1=1 and S0=1, the output Y will be connected to input D3.
So, depending on the combination of S1 and S0, the multiplexer selects one of the four data inputs and forwards it to the output line. All other data inputs are effectively disconnected from the output.
The operation of a multiplexer is not limited to 4-to-1 configurations; you can find multiplexers with different numbers of input lines based on your specific needs. Additionally, multiplexers can be cascaded to build larger multiplexers that can handle more input lines, and they are a fundamental building block in digital logic circuits.