buses and ports
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Buses and Ports
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BUSES AND PORTS 1 Bus:
Computer Bus is an electrical pathway through which the processor communicates with the
internal and external devices attached to the computer. Bus transfers the data between the
computer subsystems and between the computers and sends the instructions and commands to
and from the processor the different devices.
There are generally two buses within a computer:
1.1 System Bus: It connects all internal computer components to the main memory and the central processing unit
(CPU).as it allows the processor to communicate with the system's central memory (the RAM).
1.1.1 Types of System Bus: The address bus (sometimes called the memory bus) transports memory addresses which the
processor wants to access in order to read or write data. It is a unidirectional bus.
The data bus transfers instructions coming from or going to the processor. It is a bidirectional
bus.
The control bus (or command bus) transports orders and
synchronization signals
coming
from
the control unit and travelling to all other hardware components. It is a bidirectional bus, as it
also transmits response signals from the hardware.
1.2 Expansion Bus: It is used to connect the computer’s peripheral devices such as printer, modem and scanner
with the processor.
It allows various motherboard components (USB, serial, and parallel ports, cards inserted in PCI
connectors, hard drives, CD‐ROM and CD‐RW drives, etc.) to communicate with one another.
However, it is mainly used to add new devices using what are called expansion slots connected
to the input/output bus.
2 Ports: Ports are defined as an interface on a computer to which you can connect a device. Personal computers
have various types of ports. Internally, there are several ports for connecting disk drives, display
screens, and keyboards. Externally, personal computers have ports for connecting modems, printers,
mouse, and other peripheral devices.
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There are three types of ports: serial, parallel and USB. Serial and parallel ports are bi‐directional,
meaning data can be sent and received. Serial ports send information one bit at a time down a
single wire. You can look at it like a two‐way street. Every car in a lane travels in a single line. A
parallel port carries data several bits (8bits/1byte) at once on multiple wires much like vehicles on a
multi‐lane highway. Serial ports were basically developed for devices that didn't require speed
such as mice and keyboards, while parallel ports were used for devices that needed data to be
processed much faster, like printers.
2.1 USB Ports: The Universal Serial Bus port is a small rectangular port and is the primary way used today to
attach all kinds of devices via a USB cable. Devices must have a USB connector in order to connect
to a USB port. Mice, keyboards, printers, and digital cameras are only a few of the many devices
that can
be
USB.
Below
are
four
USB
ports
on
the
back
of
a computer.
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USB Ports & Cable
USB devices are hot‐swappable, meaning they can be plugged or unplugged without turning off the
computer. Another nice feature is that you can attach numerous devices to a computer indirectly. Called
daisy chaining, 127 devices can be connected via USB hubs. A USB hub is a small component that
contains additional USB ports. You plug it into your computer, and immediately you can connect more
devices.
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