A multiplexer, often abbreviated as MUX, is a digital electronic device that performs the function of data selection. It's commonly used in digital circuits to route one of multiple input signals to a single output line based on control signals. In essence, a multiplexer allows you to choose which input signal to pass through to the output based on the value of its control inputs.
The operation of a multiplexer can be explained as follows:
Inputs: A multiplexer has multiple data input lines, typically denoted as D0, D1, D2, ..., Dn-1, where n is the number of inputs. Each input line carries a binary signal (0 or 1), which represents the data you want to select from.
Control Inputs: A multiplexer has control inputs, usually denoted as A, B, C, ..., that determine which input line's data is routed to the output. The number of control inputs required is determined by the number of inputs (n). If there are n inputs, you need log2(n) control inputs.
Output: The multiplexer has a single output line, denoted as Y. The selected input's data will be forwarded to this output line.
Operation: The control inputs determine the binary value that represents the index of the input line you want to select. For instance, if you have a 2-to-1 multiplexer (2 inputs), you need 1 control input (A) to select one of the two inputs. If A = 0, then the output Y will carry the data from D0. If A = 1, then the output Y will carry the data from D1.
Similarly, for a 4-to-1 multiplexer (4 inputs), you'd need 2 control inputs (A and B). The combination of A and B determines which input is selected. The possible combinations of A and B would be:
A=0, B=0 -> Output Y carries data from D0
A=0, B=1 -> Output Y carries data from D1
A=1, B=0 -> Output Y carries data from D2
A=1, B=1 -> Output Y carries data from D3
In summary, a multiplexer's primary function is to provide a way to choose one out of multiple input signals based on control inputs. It's used in various digital systems such as processors, memory, communication systems, and more, where data selection and routing are essential operations.