Module 4.0

Introduction to Combinational Logic

What you´ll learn in Module 4

Binary Arithmetic


Combinational logic has many uses in electronic systems. It is used to carry out the essential arithmetic, not only in computers and calculators, but also in navigation systems, robots and many other types of automatic machinery. However complex such calculations need to be, they all depend on some basic combinational logic circuits to carry out binary addition and subtraction. This arithmetic is discussed in Digital Electronics Module 1 ‘Number Systems’

Logical Decisions


Mathematics and logical decision making also uses combinational logic in the form of Comparators, described in Module 4.3. These circuits decide whether one value is the same, larger or smaller than another value.

Data Routing


After making a logical decision, data may need to be routed to different parts of the electronic system, this routing is controlled by more combinational logic circuits such as the data selectors, multiplexers and demultiplexers described in Module 4.2.

Encoding and Decoding


When connecting a logic circuit with the outside world, the incoming information from a keyboard or other input device will almost invariably need to be changed (encoded) into an appropriate binary form. Also before binary data produced by the digital system can be used by an output device, such as a display, it must be decoded into a form that can be used by the display. Encoders and decoders used for such jobs are also combinational logic circuits, and are described in Module 4.4.

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