Combinational logic functions and Boolean algebra, logical tables, Karnaugh maps, minimization, solid execution logic and combinational logic functions
Multiplexers and Demultiplexers

Given that the transmission of information (particularly at greater distances) using a parallel bus requires a larger number of parallel conductors are used for serial information transmission lines. For example, for 16-bit parallel transfer of information over the serial line will suffice six channels of information, one locking, 4 and one addressing information.

Multiplexer (set of instructions) is a device that ensures the transfer of information transmitted in parallel on the bus to information transmitted via a serial line. Demultiplexer (selector instructions) on the other hand a device which divides the serial information to the individual bus wires.

Fig. 4.5: Multiplexer and demultiplexer function

In the left part of Figure 4.6 shows the four bit bus for which information is transmitted. Wire bus has marked V1 to V4. Information is transmitted by a parallel combination of four bits. This information enters the multiplexer (MUX), which is converted to serial bits of information in the sequence V1 to V4. Thus structured information over the serial line progresses to the demultiplexer, which decomposes it back to the bus lines.

Figure 4.6 is plotted four-channel multiplexer logic diagram. V1 to V4 inputs are data inputs (input). Inputs A and B are the address inputs and EN is blocking input. Multiplexer function describes the following logical table.

Table 5: Logical table
EN | B | A | Q
0 |  |  | 0
1 | 0 | 0 | V1
1 | 0 | 1 | V2
1 | 1 | 0 | V3
1 | 1 | 1 | V4

Fig. 4.6: Multiplexer
Pic 4.7: Demultiplexer

Figure 4.7 is plotted four-channel demultiplexer logic diagram. Q input is divided into outputs V1 to V4. Inputs A and B are the address inputs and EN is blocking input. The following describes the function of the demultiplexer logical table.

Table 6: Logical table
EN | B | A | výstup
0 |  |  | 0
1 | 0 | 0 | V1
1 | 0 | 1 | V2
1 | 1 | 0 | V3
1 | 1 | 1 | V4