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Multiplexers

Multiplexer call matching device, providing the transmission in the desired sequence of digital information, arriving on multiple inputs on one output. Denote by multiplexers MUX(from the English. multiplexor), as well as using MS(from the English. multiplexor selector). Schematically a multiplexer can be represented in the form of a switch, allows the connection of one of several inputs (they are called information) to one output device. In addition to information inputs to the multiplexer address inputs are and, as a rule, allow (gate). The signals on the address inputs determine the, what specific information channel is connected to the output. If the number of information inputs n and the number of address inputs is valid, the ratio  p = 2m, such a multiplexer is referred to as full. If n < 2m, the multiplexer is called an incomplete.

Enabling inputs used to extend the functionality of a multiplexer. They are used to increase the capacity of a multiplexer, synchronize its operation with other nodes. The signals on the enable inputs can enable, and can allow you to connect a certain input to output, t. e. can block the action of the entire device.

 

Let us consider the functioning of a two-input multiplexer (2→1), which is conventionally depicted as a switch, and the state of its inputs X,, X2 and output Y are shown in table (rice. 3.41). The table, we can write the following equation: 

 Формула Мультиплексора

In figure. 3.42 shows the implementation of such a device and its pictorial symbol. The basis of this scheme are two schemes overlap on the elements And, at which logical level "1" on one of its inputs is repeated at the output of the, what is at the other entrance.

 

Мультиплексор

If you want to expand the number of inputs, we use the cascade connection of the multiplexers. As an example, consider a multiplexer with four inputs (4→1), based on multiplexers (2→1).

Diagram and state table of this multiplexer is shown in figure. 3.43.

Multiplexers are universal logic devices, on the basis of which create various combinational and sequential circuits. Multiplexers can be used in frequency dividers, trigger devices, shearing devices, etc. Multiplexers are often used to convert the parallel code in serial binary. For this conversion, you are entitled to the information inputs of the multiplexer binary parallel code, and the signals on the address inputs to apply in this sequence, to the output of the serially connected inputs, starting from the first to the last.

Мультиплексор

Consider the example of using multiplexers to implement the so-called Raman shifter, ensure the shift of the binary number in bits. The principle of operation of this device is clear from the scheme of the device and a state table of its inputs and outputs (rice. 3.44).

In the designation of the multiplexers use two Russian letters KP, for example, industry produces such multiplexers, as К155КП1, К531КІ118, К561КПЗ, К555КП17, etc.

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