input output devices and modules in computer

INPUT OUTPUT1- Devices2- Modules3- Techniques

GROUP MEMBERS•Ammar Shaukat 11011519-073•Sadam Husain 11011519-037•Taimur Hassan NOT FOUND

INPUT OUTPUT DEVICES

•Human Readable•Machine Readable•Communication

HUMAN READABLE

1-Interact with humane.g, video display termilnals , Printers

MACHINE READABLE

•Communicate with equipment•E.g, Magnetic disk , tape , DVD , Sensors etc

COMMUNICATION•Communicate with remote devices

• Structure:

EXTERNAL DEVICES

INPUT OUTPUT MODULES

•Functions•Structure

MODULES FUNCTOINS

•Control And timing•Processor Communication•Device Communication•Data Buffering•Error Detection

CONTROL AND TIMING

•To coordinate the flow of traffic between internal resources and external devices.•E.g, Switching of task from execution to I/0

PROCESSOR COMMUNICATION• I/O Module must communicate with the processor and with the external device.•Command decoding: ( module accepts the command from processor and sent signals on control bus ) e,g READ , WRITE , SCAN etc

PROCESSOR COMMUNICATION•Data: ( exchange of data between Processor and module )•Status reporting: ( BUSY , READY )•Address recognition:( I/O Module must recognize a unique address for each Peripheral it controls )

DEVICE COMMUNICATION• I/O Module must be able to perform device communication

This involve•Commands•Status •Data

DATA BUFFERING

• I/O Module must be able to communicate at both Device and Memory Speeds

ERROR DETECTION

•Different error detection techniques used•Report error: bad disk track or paper jam•Error techniques: Parity bit etc

MODULE STRUCTURE•Signal Lines (system bus lines): Connection with rest of computer •Logic: Interact with the processor Sturcture

INPUT OUTPUT TECHNIQUES

•Programmed I/O•Interrupt Driven I/O•Direct Memory Access

PROGRAMMED I/O•Sequential manner Processing with module•Direct control of Input output operation

•Disadvantage: Processor time wastage

INTERRUPT DRIVEN I/O•Processor Issues a command to I/O

module and continues other instructions

Does not wait completion of that I/O operation.

DISADVANTAGEINTERRUPT DRIVEN I/O

•Processor time wasting but less than programmed…•Processor keeps engaged in every read or write operation from input output module.

DIRECT MEMORY ACCESS

• Module access the main memory directly without involving the processor.•And processor continue its execution without interruption after reading or writing a word.

DIRECT MEMORY ACCESS