Hardware Reference
In-Depth Information
built in, the driver translates the electrical signals sent from the mouse into positional in-
formation and indicates the status of the buttons.
ThestandardmousedriversinWindowsaredesignedforthetraditionaltwo-buttonmouse
or scroll mouse (in Windows Me or later), but increasing numbers of mice feature addi-
tional buttons, toggles, or wheels to make them more useful. These additional features re-
quire special mouse driver software supplied by the manufacturer.
Pointing Device Interface Types
Theconnectorthatattachesyourmousetothesystemdependsonthetypeofinterfaceyou
are using. Mice are most commonly connected to your computer through the following
interfaces:
• Serial interface (obsolete)
• Dedicated motherboard (PS/2) mouse port
• USB port
• Bluetooth/wireless (transceiver connected via USB)
Serial
A popular method of connecting a mouse to older PCs is through the standard serial inter-
face.Aswithotherserialdevices,theconnectorontheendofthemousecableistypically
a 9-pin female connector; some old mice used a 25-pin female connector. Only a couple
of pins in the DB-9 or DB-25 connector are used for communications between the mouse
and the device driver, but the mouse connector typically has all 9 or 25 pins present.
Because most older PCs come with two serial ports, a serial mouse can be plugged into
eitherCOM1orCOM2.Thedevicedriver,wheninitializing,searchestheportstodeterm-
ine to which one the mouse is connected. A few mouse drivers can't function if the serial
port is set to COM3 or COM4, but most can work with any COM port (1-4).
Because a serial mouse does not connect to the system directly, it does not use system
resources by itself. Instead, the resources are those used by the serial port to which it is
connected. For example, if you have a mouse connected to COM2, and if COM2 is using
the default IRQ and I/O port address range, both the serial port and the mouse connected
to it use IRQ3 and I/O port addresses 2F8h-2FFh.
See
“
Serial Ports
,
”
p.
719
(
Chapter 14
)
.
Motherboard Mouse Port (PS/2)
Most computers include a dedicated mouse port built into the motherboard. This practice
was introduced by IBM with the PS/2 systems in 1987, so this interface is often referred
