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>What
is a PS/2 Device? |
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| The PS/2 connector is used for connecting a keyboard
and a mouse to a PC compatible computer system. It is
generally considered a Legacy Device. 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 DB-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. |
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| 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. |
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| Today laptops and a large number of desktops do not
include PS/2 ports and so the port is now regarded as
a legacy interface, having been superseded by USB.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. |
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| 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.
Shorting one pin to another on a PS/2 port can easily
kill one or both micro controllers. |
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