| Working of PS2 port, parallel port, USB port, serial port and SCSI port |
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| Objectives: At the end of this lesson you shall be able to |
- define ps2 ports working
- describe parallel port working
- list serial and usb port working
- list scsi working.
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PS2 Ports:
The PS/2 standard, introduced by IBM in 1987, stands for Personal
System/2. A PS/2 port is an electronic receptacle or plug found on
computers. It accepts a PS/2 cable with a mini-DIN connector, and is
most often used to plug in a keyboard or mouse.
The PS/2 port
is female while the mini-DIN cable is male. The connector is small with a
diameter of about 1/3 inch (9.5mm). It features a metal sleeve that is
notched to ensure proper alignment when inserting it into the PS/2 port.
This protects the circular pins inside the DIN connector from becoming
bent.
The PS/2 port was initially a large DIN plug used for a
keyboard, while the mouse was commonly plugged into a serial port.
However, as modems also used serial ports, configuration conflicts
between mouse and modem became a common problem as each tried to share
the same IRQ or memory address. To fix the problem, one could purchase a
"bus mouse," or a card that could be installed in the computer and
featured a rear PS/2 port for the mouse. The PS/2 mouse was a popular
solution because it worked independent of the serial port and avoided
configuration problems. Eventually, computers incorporated two built-in
PS/2 ports, one for the keyboard and one for a mouse. |
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If
buying extension cable for your PS/2 keyboard or mouse, be sure to
check the pin configuration to ensure you are purchasing the correct
PS/2 cable. There are seven different configurations for mini-DIN plugs
that all look like standard PS/2 port plugs at a glance. The cable
should specify what equipment is it made for. S-Video cable looks
similar to mini-DIN cables, for example, but the keyed notch in the
metal sleeve and pin arrangement differ.
Parallel Ports Work: |
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Fig 1
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| IT-A1T0230 |
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If
you have a printer connected to your computer, there is a good chance
that it uses the parallel port. While USB is becoming increasingly
popular, the parallel port is still a commonly used interface for
printers.
Fig: A typical parallel port on the back of your computer
Parallel ports can be used to connect a host of popular computer peripherals: |
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- Printers
- Scanners
- CD burners
- External hard drives
- Iomega Zip removable drives
- Network adapters
- Tape backup drives
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Parallel Port Basics
Parallel
ports were originally developed by IBM as a way to connect a printer to
your PC. When IBM was in the process of designing the PC, the company
wanted the computer to work with printers offered by Centronics, a top
printer manufacturer at the time. IBM decided not to use the same port
interface on the computer that Centronics used on the printer. |
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Fig 2
IT-A1T02302
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Instead,
IBM engineers coupled a 25-pin connector, DB-25, with a 36-pin
Centronics connector to create a special cable to connect the printer to
the computer. Other printer manufacturers ended up adopting the
Centronics interface, making this strange hybrid cable an unlikely de
facto standard.
When a PC sends data to a printer or other
device using a parallel port, it sends 8 bits of data (1 byte) at a
time. These 8 bits are transmitted parallel to each other, as opposed to |
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