COMPUTERISED ORDERING SYSTEM

Computerised Ordering System

Computerised Ordering System

Introduction

The CPU (Central Processing Unit) is the intelligent part of the system. It interprets the instructions in the user program and queries the status of the inputs. Depending on these states and the program, ordered the activation of the desired outputs. The CPU comprises the following elements:

Processor

Memory system monitor

Processor

It consists of the microprocessor, the clock generator (square wave) and an auxiliary chip.

The microprocessor is an integrated circuit (chip), which makes a lot of operations that can be grouped into:

Logical type operations.

Arithmetical operations.

Checks on the transfer of information within the PLC (Lavington 2008, 90).



Memory system monitor

It is a ROM type memory, operating system and also the controller contains the following routines, included by the manufacturer.

Initialization after power up or reset.

Test routines and response to malfunction.

Exchange of information with external units.

Reading and writing at the interfaces of I /O

Basic functions of the CPU

The system ROM, the manufacturer has recorded a series of executive programs, system software and it is these programs that will access up to perform the functions.

The software system of any automaton comprises a series of basic functions performed at certain times of each cycle. In general, each controller contains and performs the following functions:

Ensure that the execution time of the user program does not exceed a certain maximum time. This function is called Watchdog.

Run the program user.

Create an image of the inputs because the user program must not directly access the entries.

Renew the status of the outputs depending on the image of the same, obtained at the end of the cycle of user program execution.

Check the system (Stokes 2007, 13).

Other Peripheral Devices

Input Devices: These enable external input data to the computer for further processing by the CPU. This data can come from various sources, the main human.

Output Devices: are they who receive information that is processed by the CPU and the breed to be perceptible to the user.

Storage Devices: Manage data store that uses the CPU so that it can make use of them once they have been removed from main memory, since this is cleared each time the computer is turned off. They can be internal, such as a hard disk or removable media such as CD.

Communication Devices: Its function is to allow or facilitate the interaction between two or more computers, or between a computer and other peripherals external to the computer.

Although the term peripheral often involves the concept of "additional but not essential", many of which are key to a computer system. The keyboard and monitor , essential in any personal computer today (they were not the first computers), are probably the most common peripherals, and many people may not consider them as such because they are usually taken as necessary part of a computer. The mouse or mouse is perhaps the clearest example of this. Less than 20 years ago, not all personal computers including this device. The operating system MS-DOS, the most common at the time, had an interface for command line that was ...