Thursday 24 January 2013

INPUT AND OUTPUT ARCHITECTURE

INTPUT AND OUTPUT ARCHITECTURE.
INPUT DEVICES
·         Papan kekunci
·         Tetikus
·         Scanner
·         CD-ROM
·         Pengawalan (controller)
OUTPUT DEVICES
·         Monitor
·         Printer
·         Disk drives
·         Floppy disk
·         CD RW-ROM
·         Speakers

Input - hantar arahan kepada CPU.
Output – terima arahan daripada CPU.

I/O devives can bee characterized by:
Behaviour : input , output , storage.
Partner : human or machine
Data rate: bytes/sec, transfers/sec.

I/O devives can bee characterized by:
·         How the component (controller, memory, processor) can be communicated each others by using bus system.
·         All component have their own bus system.
·         Graphics output – monitor.
·         Network -  LAN network.

I/O module:
·         Interface to CPU and memory.
·         Interface to one or more peripherals
·         Example : printer
Have their own interface I/O module.


Controller and timing
1.       CPU asks I/O module to check the status of attached devices.
2.       I/O module tells the status.
3.       CPU request for data transfer to I/O module if devices is ready.
4.       I/O module gather the data and transfer to the CPU.
Example : pen  drive - we put the new devices in our computer.
                  : printer -  if we would like to print something.

CPU Communication.
1.       Command decoding
·         Tulis(write) and baca (read)
2.       Devices communication
·         Involves command , status communcations.
3.       Data buffering
·         Proses ditangguhkan / kita kena tunggu sampai buffer tersebut telah bersedia.
·         Essential function to overcome speed mismaten.
·         Contoh : you tube – kita kena tunggu juga walaupun kita dah tekan butang mainkan.
: printer -  kitanak print nota, printer tutakterus print nota tu sebab dia nak baca dulu data kita baru dia akan print seperti yang diminta.
4.       Error detection
·         Paper jam or stunk , bad data etc.
·         Contoh :printer - kita nak print nota tapi kertas sudah habis jadi dia akan keluarkan pop up di skrin komputer untuk bagi tahu kita yang kertas tiada.

I/O system characteristics
·         kebergantungan sangat penting
§  selalunya apabila kita naks impan devices
·         mengukur setiap persembahannya.
§  Latency (tindakbalas terhadap masa melalui desktop dan embedded)

INTERCONNECTING COMPNENT
Ø  Need interconnecting between CPU, memory, I/O controller.
Ø  Bus : share communication channel
o   Can became a bottleneck.
Ø  Performance limited by physical factors
o   Wire length, number of connections
Ø  More recent alternative : high-speed serial connections with switches.
o   Like network.


I/O MANAGEMENT
·         I/O is mediated by the operating system.
§  Multiples program shared I/O resources.
Ø  Need protection and scheduling.
§  I/O causes synchronous interrupts.
Ø  Same machine as exceptions
§  I/O programming is fiddly.
Ø  Operating system abstractions to program..

                                                                                                                                   -nurul ain farhana-

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