PS/2 CONNECTOR

The 'PS/2 connector' is used for connecting a keyboard and a mouse to a PC compatible computer system. Its name comes from the IBM Personal System/2 series of personal computers, with which it was introduced in 1987. The PS/2 mouse connector generally replaced the older DE-9 RS-232 "serial mouse" connector, while the keyboard connector replaced the larger 5-pin DIN used in the IBM PC/AT design. The keyboard and mouse interfaces are electrically similar with the main difference being that open collector outputs are required on both ends of the keyboard interface to allow bidirectional communication. Normal desktop motherboards will not identify the keyboard and mouse if they are placed on each other's sockets.

Contents

Port availability

Color code

Potential damage

References

See also

External links

Port availability

In the 386, 486 and Pentium era, the connectors were also seen on some PC clones with non-standard case designs and the PS/2 mouse connector was sometimes seen on a separate backplate on systems using a standard AT case. However PS/2 ports only became the norm much later with the introduction of the ATX form factor. The design decision for identical but incompatible connectors would prove aggravating to consumers. To help alleviate this, PS/2 keyboard and mouse connectors were later color-coded: purple for keyboards and green for mice as defined by the Microsoft PC 97 standard.
Old laptops generally have a single port that supports either a keyboard or a mouse. Sometimes the port also allows one of the devices to be connected to the two normally unused pins in the connector to allow both to be connected at once through a special splitter cable. The mouse interface is somewhat different from RS-232 (which was generally used for mice on PCs without PS/2 ports) but nonetheless many mice were made that could operate on both with a simple wiring adaptor.
PS/2 mouse and keyboard connectors have also been used in non-PC compatible computer systems, such as the DEC AlphaStation line, and SGI Indy, Indigo 2, and newer (Octane etc.) computers.^[1]
Today's laptops frequently do not include PS/2 ports and so the port is now regarded as a legacy port, having been superseded by USB. Many current keyboards and mice support both USB and PS/2 with a simple wiring adaptor and active adaptors are available which plug into a USB port and provide a pair of PS/2 ports.

Color code

Original PS/2 connectors were black. Later PC 97 color code was introduced.

Color		Description
	Purple	Keyboard
	Green	Mouse

Potential damage

PS/2 ports are designed to connect the digital I/O lines of the microcontroller in the external device directly to the digital lines of the microcontroller on the motherboard. They are not designed to be hot swappable. Hot swapping PS/2 devices usually does not cause damage due to the fact that more modern microcontrollers tend to have more robust I/O lines built into them which are harder to damage; however, hot swapping can still potentially cause damage on older machines, or machines with less robust port implementations.
If they are hotswapped, the devices must be similar enough that the driver running on the host system recognizes, and can be used with the new device. Otherwise, the new device will not function properly. While this is seldom an issue with standard keyboard devices, the host system rarely recognizes the new device attached to the PS/2 mouse port.

References

1.

See also

★ Bus mouse

External links

★ PS/2 keyboard and mouse mini-DIN 6 connector pinouts

★ PS/2 In-depth information on PS/2

★ Technical information on Interfacing with the AT keyboard