User guide

support.dell.com I/O Ports and Connectors B-3
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The system has an autoconfiguration capability for the serial ports. This feature lets
you add an expansion card containing a serial port that has the same designation as
one of the built-in ports, without having to reconfigure the card. When the system
detects the duplicate serial port on the expansion card, it remaps (reassigns) the built-
in port to the next available port designation.
Both the new and the remapped COM ports share the same interrupt request (IRQ)
setting, as follows:
COM1, COM3: IRQ4 (shared setting)
COM2, COM4: IRQ3 (shared setting)
These COM ports have the following I/O address settings:
COM1: 3F8h
COM2: 2F8h
COM3: 3E8h
COM4: 2E8h
For example, if you add an internal modem card with a port configured as COM1, the
system then sees logical COM1 as the address on the modem card. It automatically
remaps the built-in serial port that was designated as COM1 to COM3, which shares
the COM1 IRQ setting. (Note that when you have two COM ports sharing an IRQ set-
ting, you can use either port as necessary but you may not be able to use them both
at the same time.) If you install one or more expansion cards with serial ports desig-
nated as COM1 and COM3, the corresponding built-in serial port is disabled.
Before adding a card that remaps the COM ports, check the documentation that
accompanied your software to make sure that the software can be mapped to the
new COM port designation.
To avoid autoconfiguration, you may be able to reset jumpers on the expansion card
so that the card's port designation changes to the next available COM number, leaving
the designation for the built-in port as is. Alternatively, you can disable the built-in
ports through the System Setup program. The documentation for your expansion card
should provide the card's default I/O address and allowable IRQ settings. It should
also provide instructions for readdressing the port and changing the IRQ setting, if
necessary.
The built-in parallel port has autoconfiguration capability through the System Setup
program; that is, if you set the parallel port to its automatic configuration and add an
expansion card containing a port configured as LPT1 (IRQ7, I/O address 378h), the
system automatically remaps the built-in parallel port to its secondary address (IRQ5,
I/O address 278h). If the secondary port address is already being used, the built-in
parallel port is turned off.
For general information on how your operating system handles serial and parallel
ports, and for more detailed command procedures, see your operating system
documentation.