Measurement Computing PCI-COM422/485 - Manual (Page 11)

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If the divider is set to divide by four, (the default setting) the board’s baud rate is exactly as Windows sets it. If the
divider is set to divide by two, the actual board baud rates become double what Windows has set them to. If the
divider is set to divide by one, the board’s baud rate is four times the baud rate set in Windows. These selections are
summarized in the table below.
UART Windows Actual
Clock Rate Divider Setting baud rate
1.8432 MHz 4 (default) 115.2 kbps 115.2 kbps
3.6864 MHz 2 115.2 kbps 230.4 kbps
7.3728 MHz 1 115.2 kbps 460.8 kbps
Note: Please pay very careful attention to your baud rate selections when using the extended baud rate operating
modes. The baud rate you select in windows will not be the actual baud rate setting of the PCI-COM board, and it is
easy to get confused regarding the speed at which the system is actually running.
2.6.1 WINDOWS 95 OR 98 SPEC IFIC CONFIGURATION
Extended baud rate operation is set on the COM port’s property page. To change to the enhanced baud rate
operating modes follow this procedure.
1. Right click on the “My Computer” Icon on your desktop.
2. Click on “Properties”.
3. Click on the “Device Manager” tab.
4. Double click on the “Ports (COM & LPT)” Icon.
5. Double click on the port you wish to configure.
6. Click on the “Advanced” tab.
7. Select the desired UART clock rate from the radio buttons as shown in Figure 2-5:
Figure 2-5. PCI-COM422/485 (Port1) (COM3) Properties Screen Display