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Configuring NI Serial Boards to Use COM1 Through COM4

Hardware: PXI/CompactPCI>>Controllers

Problem:
How do I assign the serial ports of my National Instruments serial card to COM1, COM2, COM3, and/or COM4?

Solution:
The NI 843x family of high-performance serial boards are memory mapped and do not use I/O address space. Therefore, the following information does not apply to the NI 843x series.

The names COM1, COM2, COM3, COM4 are assigned by changing the base address assigned to the port to be the standard base address for the respective COM port:
   COM1   3f8
   COM2   2f8
   COM3   3e8
   COM4   2e8
To change the base address of a port in Windows 98, go to Start » Settings » Control Panel » System » Device Manager and open the Multifunction Adapters listing to reveal the parent device for your serial board. (You will not be able to change the base address under the board properties themselves.) Select the parent device for your serial board and press the Properties button. Go to the Resources tab and change the base address to the address of the COM port you want to use.

In Windows NT, you can change COM ports by going to Start » Settings » Control Panel » NI Ports. Here you can select the COM ports from a pull down menu.

In Windows 2000 and XP, go to Start » Settings » Control Panel » System » Hardware » Device Manager. Under "Ports", select the port you would like to change and open the Properties dialog box. Go to Port Settings » Advanced and select the COM port number to assign to the physical port.

If you need to change more than one port's address, you must change them one at a time and Reboot after each new assignment.

Note: This can only be done with the 2 and 4-port serial boards; the base address of the 8-port serial boards (e.g., PCI-232/8) cannot be modified. The reason for this is that, unlike the 2 and 4 port boards which actually get assigned memory addresses on a per port basis, the multifunction adapter for the 8 port board is assigned an upper memory block.

Related Links:
Knowledge Base 2E1ET4LS: Problems with COM Port Reassignments for PXI Serial Hardware on a MXI-3 or MXI-4 System

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Report Date: 03/26/1998
Last Updated: 01/20/2009
Document ID: 17PHB8TI

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