Input Output Ports And Devices

Objectives :

  • Introduce ports
  • Identify the different ports
  • Work with the IEEE 1394 bus
  • Configure IRQ
  • Troubleshoot ports

Ports and it's back panel view :

Entry and exit point for data from the system

Connects the system and a device using a connecting cable

Located at the back or the front side of the system case

Ports have different shapes and sizes and you can not insert a plug in the wrong port

You can just unplug a device that is not used and plug in another device in that port


Port :

Identifies the type of the port


Types of Ports :


Serial Port :

Sends and receives one bit of data at a time

Known as the Communication or COM port

Has 9 or 25 pins

Connect devices such as the mouse, plotters and modems

Transmitting device sends a start bit then actual data byte followed by a stop bit

Maximum cable length is 50 feet

If you need more serial ports, you can install multi I/O card


Parallel Port :

Transmits eight bits of data at a time

Has 25 pins

Connects devices such as printers, scanners, external hard drive and tape drive

You can get more parallel ports by installing an expansion card

LPT1 uses IRQ7 and LPT2 uses IRQ5


Different types of parallel ports are :

  • Bidirectional – Uses byte and compatible mode for data transmission
  • Standard Parallel Port (SPP) - Uses nibble and compatible mode for data transmission
  • Enhanced Parallel Port (EPP) - Provides data transfer speed of 500 Kb to 2 Mb of data per second. It is built into super I/O chip or south bridge chip on motherboard
  • Enhanced Capabilities Port (ECP) - Provides increased data communication speed to connect printer or scanner and supports DMA

IEEE 1284 :

Compatibility Mode – used for directing data from computer to peripheral (output only)

Nibble Mode – 4 bit (Input only)

Byte Mode – uses software drivers same as nibble mode (8 bit)

Enhanced Parallel Port Mode (EPP) – it is hardware driven and bi-directional, high speed parallel port interface

Enhanced Capability Port Mode (ECP) – same as EPP uses DMA

PS/2 :

Used to connect the keyboard and the mouse

Available in a color that matches the color of the device plug

Uses 6 pins to connect the device


Universal Serial Bus (USB) :

Connects upto 127 devices to a single port

Supplies power to the device

Plug-and-play support

Maximum cable length is 30m thus you can connect 5 hubs to the USB

Has two different connections: connection A and connection B

USB 1.0 – 1.5 Mbps, USB 1.1 – 12 Mbps and USB 2.0 – 480 Mbps


Infrared Ports :

Communicate with the system without using wires

Devices send out infrared signals that enter the system through this port


Bluetooth Port :

Allows wireless communication between devices within a ranged distance

Uses 2.45 GHz frequency range for data communication

A Bluetooth adapter required for the computer and a Bluetooth compatible device to communicate

Speed is 1 or 2 Mbps depending on the version


IEEE 1394 Bus :

Enables fast and high serial data transfer rate of upto 400 Mb per second

Connects and supplies power to the connected devices such as printer, scanner, web camera and generally used for transferring audio and video data from a camera to the system

Known as FireWire by Apple and iLink by Sony


Wireless LAN USB Adapter :

Connects computer to wireless LAN

By using this adapter desktop, notebook and laptop users can connect to a standard mobile network

Plugged to computer through a USB port

Data Transfer Rate is 54 Mbps

Troubleshooting :

While using the device, errors may occur if there is a problem with the I/O port

Different types of problems related with IO port :

  • Device not working properly
  • IRQ conflicts
#Input_Output_Ports_And_Devices #Ports_and_its_back_panel_view #Port #Types_of_Ports #Serial_Port #Parallel_Port #Different_types_of_parallel_ports #IEEE_1284 #PS/2 #Universal_Serial_Bus_(USB) #Infrared_Ports #Bluetooth_Port #IEEE_1394_Bus #Wireless_LAN_USB_Adapter #Troubleshooting_Input_Output_Ports

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