Dell Precision 420 - Manual (Page 72)

Keyboard and Mouse Connectors Overview
Your system uses a Personal System/2 (PS/2)-style keyboard and supports a PS/2-compatible mouse. Cables from both devices attach to 6-pin
miniature Deutsche Industrie Norm (DIN) connectors on the back panel of your computer.
A PS/2-compatible mouse works identically to an industry-standard serial mouse or bus mouse except that it has its own dedicated connector,
which frees up both serial ports and does not require an expansion card. Circuitry inside the mouse detects either the movement of a small ball or
the input from an optical sensor and relays the direction to the computer.
Mouse driver software can give the mouse priority with the microprocessor by issuing IRQ12 whenever a new mouse movement is made. The
driver software also passes along the mouse data to the application program that is in control.
Keyboard Connector
If you reconfigure your hardware, you may need pin number and signal information for the keyboard connector. Figure 7 illustrates the pin numbers
for the keyboard connector, and Table 6 lists and defines the pin assignments and interface signals for the keyboard connector.
Figure 7. Pin Numbers for the Keyboard Connector
Table 6. Pin Assignments and Interface Signals for the Keyboard Connector
Mouse Connector
If you reconfigure your hardware, you may need pin number and signal information for the mouse connector. Figure 8 illustrates the pin numbers for
the mouse connector, and Table 7 lists and defines the pin assignments and interface signals for the mouse connector.
Figure 8. Pin Numbers for the Mouse Connector
57 BSY I/O SCSI busy
58 ACK I/O SCSI acknowledge
59 RST I/O SCSI reset
60 MSG I/O SCSI message
61 SEL I/O SCSI select
62 C/D I/O SCSI command/data
63 REQ I/O SCSI request
64 I/O I/O SCSI in/out
65 D8 I/O SCSI data bit 8
66 D9 I/O SCSI data bit 9
67 D10 I/O SCSI data bit 10
68 D11 I/O SCSI data bit 11
Pin Signal I/O Definition
1 KBDATA I/O Keyboard data
2 NC N/A No connection
3 GND N/A Signal ground
4 FVcc N/A Fused supply voltage
5 KBCLK I/O Keyboard clock
6 NC N/A No connection
Shell N/A N/A Chassis ground