characterbaseddevices

characterbaseddevices - Character Based Devices Computer...

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Computer Engineering Character Based Devices
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Computer Engineering Input-Output Devices • What are I/O devices? Accept data from external source (e.g. keyboard, mouse) Present data to outside world (e.g. monitor, printer) Store data away from CPU (e.g. disk drives, magnetic tape) • Connect CPU to outside world!
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Computer Engineering Computer Peripheral Devices Central Processor Modems Printers Disks Terminals Tapes kB/s MB/s B/s kB/s MB/s
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Computer Engineering Intro to I/O • Design of computer system - optimization of many parameters • Maximize use of each component • I/O mechanical – convert mechanical inputs into electrical signals (e.g. keyboards) +vice versa (e.g. printers) • Mechanical systems – SLOW, why? – Power requirements – Structural requirements – Thermal restrictions
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Computer Engineering Intro to I/O • I/O devices classified in terms of: – modes of operations (mechanical, electrical), – speed • Electrical communication: serial, parallel • Focus here on serial communication of devices with rest of computer system: sequential transmission of bit streams
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Computer Engineering Character-based I/O • Focus on PC, workstation • People need to communicate with computer • Use keyboard, mouse to enter information • Monitor, printer display info from machine • Modes of communication alter perception of computer • People absorb data much faster than produce it – keyboard limits speed of data transmission
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Computer Engineering Character-based I/O • Terminal (old terminology) = input + output device Character-based I/O device – devices that communicate by passing 1 character at a time • Start with keyboard – primary mechanism for text input to computer
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Computer Engineering Alphanumeric Printing Terminal • Requirement – Transmit and Receive single characters over a two wire connection. – “Low” speed communication.
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Computer Engineering Keyboard • Process – Recognize a mechanical impulse – Encode as a sequence of electrical pulses – Transmit along a wire – Receives pulses and converts to a parallel format – Place on computer bus - set of electrical circuits used to move signals representing information between devices
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Computer Engineering Keyboard Electronics • Mechanical Impulse Conversion – The input device (keyboard) consists of a set of labeled keys corresponding to characters (letters, numbers, special symbols) • Each key is connected to a switch V A B Pressing on A creates a voltage, V, at B. The switch may be: mechanical inductive, capacitative,. ..
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Keyboard Electronics • Purpose – translate character into ASCII code, transmit to CPU • If every key is connected to its own switch then for any “character” selection only one line will have a voltage. – For a 64 key keyboard this would result in 64
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This note was uploaded on 11/22/2010 for the course ECSE ECSE 322 taught by Professor Lowther during the Winter '04 term at McGill.

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characterbaseddevices - Character Based Devices Computer...

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