Applied PC Interfacing, Communications and Graphics

The number of devices which connect to PCs seems to increase by the year. This is mainly due to the increasing processing power of PCs and also the availability of large amounts of electronic memory. A typical modern PC now contains devices such as a hi-resolution graphics display, a hard-disk, a floppy-disk, a sound card, a modem, a CD-ROM drive, serial and parallel ports, and so on.

Author: Dr W.Buchanan, Napier University, Edinburgh. Downloads: Source code emulator TOC Review Details: Addison-Wesley 0-201-87728-7		The objective of this text is to provide an understanding of how devices are programmed using software and also how they integrate to create a system. This should help in the writing of interface software and should also provide an understanding of system specifications.
		Tutorial and project work relates to practical programming examples. Projects include the development of a traffic light controller, a real-time serial communications system, an air-conditioning system, a mouse-driven menu system and a graphics package for displaying electronic circuits.
		The book is primarily aimed at Engineering and Computer Science students. It can also be used by professionals in industry as it discusses key interfacing areas, especially related to interrupts, graphics and serial communications. Discussion of the electrical aspects of the interface devices, such as voltages and currents has been kept to a minimum as this would spoil the flow of the text.

The main areas covered are digital interfacing, counter/timer interfacing, analogue interfacing, serial communications, direct memory addressing, direct video text interfacing, graphics, mouse interfacing, keyboard interfacing, disk interfacing, interrupts and file access. Chapters on digital input/output, counter/timing and analogue interfacing require extra hardware to connect to the PC, but most other chapters use standard PC hardware, such as serial communication, mouse interfacing, keyboard interfacing, graphics, and so on. To reduce the need for external hardware a software emulator is included to emulate calls to digital input/output devices.

The text uses C as the main software language as it allows low-level, direct access to the hardware. In earlier chapters Turbo Pascal and Assembly Language are used to show how different software languages can be used to implement equivalent C programs.

Many books currently on the market only discuss how PC hardware interconnects and how Assembly Language communicates with them. This can be confusing, or even off-putting, as most industry programs are written using high-level languages. Assembly Language is normally only used when high-speed operations are required, it also gives little scope for keyboard input and output, disk operations and also for graphics.

Over the years I have been involved in consultancy work with several companies. Much of this work has involved interfacing PCs to remote instrumentation. Typically these instruments process their data and transmitted it in a digital form using RS-232 communications. This interface an cause many problems, including the use of different connectors, different frame formats, different connections, differing handshaking, and so on. It is for this reason I have included a whole chapter on the theory of serial communications and how software can be written to control it. The usage of serial communications will increase as many electronic systems now have an RS-232 connector fitted as standard. It provides an excellent method to send and receive data from remote systems. I have met many people who use RS-232, and have even written programs which use it, but they have little understand about its operation. It provides one of the best interfacing examples as it is available on all PCs and requires only two PCs and an interconnecting cable.

Another area which I feel is lacking in many books is the coverage of hardware and software interrupts. This book discusses these and shows how a practical system uses then to connect external hardware. It also shows how a program accesses functions to communicate with standard devices, such as reading from the keyboard or outputting text to the screen. Accessing memory directly is also discussed and the text shows how to access up to 1 MB of physical memory using a C program. Background theory on video displays and memory is provided in the appendices as well as an introduction to C.