Troubleshooting Tips

The following are troubleshooting tips for Windows operating system problems you may encounter.

Problem: Conflicting Interrupt Requests (IRQs) or base addresses.

When you are working with serial COM ports in Windows, you may have a problem with conflicting Interrupt Request (IRQ) and Input/Output Range settings for COM ports or other devices configured to the system.

Suggested Resolution:

For Windows 95/98/Me: To change the IRQ or Input/Output Range settings, select the Control Panel, System, Device Manager tab, and Communications Port. Double-click on Communications Port or the appropriate COM port. Select the Resources tab to display the Resource Type and Setting dialog box where you can change the settings.

For Windows NT or newer: To change the IRQ or Base I/O Port settings, select the Control Panel and double-click on Ports to display the Ports dialog box. Select the COM port, the Settings button, and the Advanced button to display the Advanced Settings for COMn dialog box. Change the IRQ or Base I/O Port Address settings in this dialog box.

Problem: 16550 UART at minimum baud rate of 9600 is needed.

The Windows driver supports RS-232 ports that are based on the 16550 UART, the chip that controls the serial port. The 16550 UART is known to work better at baud rates higher than 9600, since it has a FIFO (First In First Out) buffer.

Suggested Resolution:

A minimum configuration of a 16550 UART at a baud rate of at least 9600 is suggested. Make sure that the Use FIFO buffer or FIFO Enabled setting is selected.

For Windows 95/98/Me: To change the baud rate, select the Control Panel, System, Device Manager tab, and double-click on Communications Port (COMn). Select the Port Settings Tab and change the entry for Bits per second. To check the FIFO buffer settings, click on the Advanced button to display the Advanced Port Settings dialog box. Make sure the Use FIFO buffers checkbox is selected.

For Windows NT: To change the baud rate, select the Control Panel and double-click on Ports to display the Ports dialog box. Select the COM port, the Settings button, and change the Baud Rate setting in the Settings for COMn dialog box. To check the FIFO settings, click the Advanced button to display the Advanced Settings for COMn dialog box. Make sure the FIFO Enabled checkbox is selected.

Note: For more information, refer to the Microsoft Windows User Guide.