Page 117 - DCAP210_INTRODUCTION__TO_MICROPROCESSORS

Unit 8: Interfacing I/O Devices

Objectives Notes

After studying this unit, you will able to understand the following:
• Describe Basic interface concepts

• Explain graphical user interface
• Discuss I/O devices in microprocessor
• Explain the memory mapped I/O

Introduction

An I/O interface is required whenever the I/O device is driven by the processor. The interface
must have necessary logic to interpret the device address generated by the processor. Handshaking
should be implemented by the interface using appropriate commands (like BUSY, READY, and
WAIT), and the processor can communicate with an I/O device through the interface. If different
data formats are being exchanged, the interface must be able to convert serial data to parallel
form and vice-versa. There must be provision for generating interrupts and the corresponding
type numbers for further processing by the processor if required.

A computer that uses memory-mapped I/O accesses hardware by reading and writing to specific
memory locations, using the same assembly language instructions that computer would normally
use to access memory.

8.1 Basic Interface Concepts
Interfacing is a textile used on the unseen or “wrong” side of fabrics to make an area of a garment
more rigid.
Interfacings can be used to:
• stiffen or add body to fabric, such as the interfacing used in shirt collars

• strengthen a certain area of the fabric, for instance where buttonholes will be sewn
• keep fabrics from stretching out of shape, particularly knit fabrics
Interfacings come in a variety of weights and stiffness’s to suit different purposes. Generally, the
heavier weight a fabric is the heavier weight an interfacing it will use. Most modern interfacings
have heat-activated adhesive on one side. They are affixed to a garment piece using heat and
moderate pressure, from a hand iron for example. This type of interfacing is known as “fusible”
interfacing. Non-fusible interfacings do not have adhesive and must be sewn by hand or machine.
There are a lot of places where you’ll see text that looks like this. Apart from this example, that
color and style of text indicates a tip. Just hover your mouse over the text and you’ll get a hovering
window that gives more information. Generally, the game’s most crucial concepts will be explained
here, so make good use of these elements!

Until you turn them off, most pages will come standard with page tips that tell you a bit about
what the page are all about. Sometimes these tips are very useful! Try to keep the tips on until
you’re truly familiar with the inner workings of the game

8.2 Graphical User Interface
It is a type of user interface that allows users to interact with electronic devices with images
rather than text commands. GUIs can be used in computers, hand-held devices such as MP3
players, portable media players or gaming devices, household appliances and office equipment.
A GUI represents the information and actions available to a user through graphical icons and

LOVELY PROFESSIONAL UNIVERSITY 111