Sunday, July 20, 2014

Fundamentals of Computer Communications

In search of fundamentals of computer communications in CIM? This article will be of great help to you. Read it completely to know what all the concepts are there, how the transformation of information in CIM takes place, etc.

Some common terms relating to communications are: Data - entities that covey meaning, Information - the content or interpretation of data, Signals - electric or electromagnetic encoding of data, Signalling - the act of propagating of data by processing of signals

Note that data and information are not the same thing. Data is raw, whereas is processes data. Information displays some useful message, whereas data merely contains it. Nonetheless, as is common practiced, this text uses the terms data and interchangeably. In manufacturing, as elsewhere, data and information are generated, collected, manipulated, transmitted, stored, retrieved, plotted, and shared.

Data communication using computers began with minicomputers. Later, when microcomputers became inexpensive and powerful, data communications applications proliferated. In fact, microcomputers were developed with communications in mind. That is obvious from their serial asynchronous communication capability through RS-232 as well as the parallel ports. Despite this standard, however, there are incompatibility problems. RS-232 ports limit the distance between the communicating devices. Paper and magnetic tapes were developed as alternatives to direct online communication. While they are used to move large amounts of data between devices separated by any distance, their drawback is the requirement for physically moving the data.

Regardless of the types of source and destination, the computer or terminal usually serves as a communication link in CIM environments. Consider, for example, the case of a machine tool operator who requires input, say a part program, from the plant host computer. The operator sends a request through the machine control unit (MCU) to the host, which downloads the program. In effect, then, communication between the operator and machine occurs via a computer, the MCU.

As with human conservation, computer communication involves three levels: cognitive, language, and transmission. The cognitive level requires that the devices have enough intelligence to take part in communication. The language level demands that both understand a common language. The transmission level requires a physical mechanism for information transfer. Each of three levels of the sender must be compatible with that of the receiver. Human communication follows some rules (etiquette or protocol). Even when they are broken, they allow communication. For example, a speaker who does not possess high proficiency in English or has a difficult accent can still be understood. The protocols of computer communications do not allow such variations.

Most computer communications take place in a way similar to communication between two individuals. Communications technology principles are easier to comprehend if we keep  in mind the situation of two persons communicating with each other. Consider, for example, what is happening at this moment between you as a reader and me as a author. Whatever I have to say about communications relating to CIM is here in this page you are reading. We are communicating with each other , albeit in a one-way mode (only from author to reader). In a two-way mode, called bidirectional, the communicating partners or devices change their roles of receiver and transmitter as and when required.

Irrespective of the mode, whether unidirectional or bidirectional, communication between two participants such as persons, computers, machines, or any combination, involves these three components: Transmitter or sender - the source of information, Receiver - the person or device needing the information, Medium - the path through which information flows.

In addition, a language - the protocol - must exist for communications to take place. In our example of communications between you and me, I represent the transmitter, you the receiver, this article the medium, and the English the protocol. The process of transferring information within CIM involves three basic issues: 1. Representation and signalling of data, 2.Medium and 3. Networking of devices which will be later in separate articles.
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