designation.
Both the new and the remapped COM ports share the same 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 computer then see s 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 setting, 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 designated as COM1 and COM3, the corresponding built-in serial port is disabled, as described in "Serial Port 1 and Serial Port 2".
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 the expansion card's jumpers or switches so that its 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 more information, see "Parallel Port".
For general information on how your operating system handles serial and parallel ports as well as for more detailed command procedures, see your operating system documentation.
Serial Port Connectors
If you reconfigure your hardware, you may need pin number and signal information for the serial port connectors. Figure B-3 illustrates the pin numbers for the serial port connectors, and Table B-3 lists and defines the pin assignments and interface signals for the serial port connectors.
Figure B-3. Pin Numbers for the Serial Port Connectors
Table B-3. Pin Assignments for the Serial Port Connectors
Pin | Signal | I/O | Definition |
1 | DCD | I | Data carrier detect |
2 | SIN | I | Serial input |
3 | SOUT | O | Serial output |
