# Initial information about combinational devices, Methods of...

## Ways of presenting and describing combinational devices

Consider them.

### Graphical method

The combination device can be represented as a multi-terminal (Figure 3.2), with M inputs, which are fed signals X m (m = 0, ..., M - 1), and N outputs from which the signals Y n (n = 0, ..., IV-1). This type of representation is called graphic or schematic. It is used to compile logic circuits of digital devices.

### Analytical method

The peculiarity of both input X m and output Y n signals is that they can take only two values ​​- 0 and 1. Since in combinational devices signals Y n are uniquely determined by the combination (combination) of signals {X m }, acting on a certain time interval T,

Fig. 3.1. Ways of processing and inputting/outputting code words: sequential input and output (a), parallel input and output (b), serial input - parallel output (in), parallel input - serial output ( > g )

then in the general case the relationship between them can be specified in the form of a system of logical functions

(3.1)

Fig. 3.2. Graphical representation of a combination device

The system (3.1) is an analytical description of combinational devices.

### Tabular method

One of the most common ways of describing combinational devices is truth tables. The truth table contains:

• One column for storing numbers k or combinations of sets of input signals (decimal number, starting with zero);

M , which is usually identified columns for recording values ​​of the input signals with binary numbers and arranged in rows of the table in ascending order. Combinations of 0 and 1 make it possible to obtain K = 2 m different values ​​of numbers. For example, for M = 2 binary numbers take on the following values: 00, 01, 10, 11. Each k-u set (combination) of the input signals corresponds, according to (3.1) determined output value and on th Raman device output;

N columns for recording the values ​​of the output signals

The structure of the truth table for M = 2 is given below as an example (Table 3.2). The truth table provides exhaustive information about the functionality of the combination device and is widely used to describe them.

Table 3.2

 k Input signals Output signals 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 0 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 2 1 0 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 3 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

[...]

[...]

[...]

[...]

[...]

[...]

[...]

[...]

[...]

[...]

[...]

[...]

[...]

[...]

## Other services that we offer

If you don’t see the necessary subject, paper type, or topic in our list of available services and examples, don’t worry! We have a number of other academic disciplines to suit the needs of anyone who visits this website looking for help.

## How to ...

We made your life easier with putting together a big number of articles and guidelines on how to plan and write different types of assignments (Essay, Research Paper, Dissertation etc)