Digital system

Digital watch.

A binary digital system is a set of devices that are intended for the generation, transmission, management, processing and storage of digital signals. Also, and unlike an analog system, a digital system is a combination of devices designed to manipulate physical quantities or information that is represented in digital form; that is, it can only take discrete values.

For the analysis and synthesis of binary digital systems, Boolean algebra is used as a tool.

• Combined digital systems: Those whose exits depend only on the status of their entries at a given time. Therefore, they do not need memory modules, as the outputs do not depend on the previous states of the entries.

• Sequential digital systems: Those whose departures depend, in addition to the status of their entries at a given time, on previous states. This kind of systems need memory elements that store the different states to get the results.

For the implementation of digital circuits, logic gates (AND, OR and NOT) are used, generally built from transistors. These gates follow the behavior of basic Boolean functions.

According to the purpose of digital systems, they are classified as:

1. Special purpose systems. These have a fixed programming that allows you to execute specific tasks.
2. General purpose systems. These allow the change of their behavior by programming algorithms, which gives solutions to various problems. Most modern computers are general purpose digital systems.

General model

• Combined digital systems:

Z = F(X)

Z= value signals of the outputs; X= value signals of the inputs; F= signal transformer circuit (electronic gates)

• Sequential digital systems:

Z = F(X,Q)

Z= value signals of the outputs; X= value signals of the inputs; Q= memory elements (Flip Flops); F= signal transformer circuit (electronic gates)

Combinational Circuit Design

Step 1. Problem statement

Step 2. Analysis: Specification of input and output variables

Step 3. Modeling: Defining the Boolean functions that specify the behavior of the system

Step 4. Simplifying Boolean functions (optionally)

Step 5. Logic diagram

Step 6. Selection of integrated circuits

Step 7. Digital system assembly (breadboard or pre-printed circuit)

Step 8. Testing

Types of combinational circuits

• Code converters: Decoders and coders
• Flow selectors: Multiplexers and demultiplexers
• Burners:Full media and summaries
• Comparisons
• Reading-only memory

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