System Design Applications

Decoders are often used in microprocessor systems to decode the address information from the microprocessor in order to select the correct memory chip. A popular IC for this application is the 74138 or 74HCT138.
Encoders are often used in microprocessor or in microcontroller applications to combine or group a large number of inputs down to a smaller binary count of the input activity. The 74148 is a popular IC encoder chip for these kinds of applications.
Microprocessor based systems with serial input and output ports can use multiplexers and demultiplexers to route serial data to and from a number of different destinations. Multiplexers are used to combine several inputs into one and demultiplexers, or data distributors are used to send a single output to one of several destinations.
An analog multiplexer can be used as a staircase generator which in turn can be used to provide a multiple input for an oscilloscope.
A multiplexer/demultiplexer can be used to multiplex a 7-segment display system.