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Understand I/O in Computer System - Coggle Diagram
Understand I/O in Computer System
I/O Module
describe any program, operation or device that transfers data to or from a computer and to data or from a peripheral
device.
Every transfer is an output from one device and
an input into another
Function
Acts as an interface with the CPU and memory
via the system bus or central switch
Acts as an interface with one or more
peripheral devices by tailored data links.
I/O devices
output
monitor
speaker
both input/output
fax machine
modem
input
keyboard
mouse
Input/Output Data Transfer
Each character transmitter consists of a start bit,
character bits, and stop bits
The first bit is called the start bit. It is always a 0 and is
used to indicate the beginning of a character
Asynchronous serial transmission is character oriented
The last bit called the stop bit is always a 1
characteristic
Memory mapped I/O
I/O looks just like memory read/write
No special commands for I/O
Devices and memory share an address
space
Large selection of memory access
commands available
Isolated I/O
Need I/O or memory select lines
Special commands for I/O
Separate address spaces
Limited set
transfer mode
Interrupt-Initiated I/O
I/O module interrupts when ready
No repeated CPU checking of device
Overcomes CPU waiting
Direct Memory Access
method of transferring data between peripherals and
memory without using the CPU
CPU may not be fast enough to
keep up with the peripheral
The DMA controller periodically takes over
control of the system bus from the CPU
generates address, data and control
signals to transfer data between memory and
I/O devices
Programmed I/O
method of transferring data between
the CPU and a peripheral
network adapter
ATA storage device
happens when software running on the CPU uses instructions
that access I/O address space to perform data transfers to or from an I/O device
pros
Simple to implement
cons
CPU is tied up for the duration of the transfer
while doing a relatively simple task