Measurement Computing PCI-COM232 - Manual (Page 8)

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Figure 2-1. TTY Settings
4. Launch the ComApp again. You will get a second ComApp window. Go to the Settings
menu and configure the second port. Note that you must use the same settings on both ports
for this test to work properly.
5. On both open ComApp windows, go to the Action menu and select Connect.
6. Once connected, move the cursor to either ComApp window. Whatever is typed in that
window should be immediately displayed in the other. You may also test port operations by
selecting the Transfer menu and clicking on Send Data Block. A large block of ASCII
characters will automatically be sent, and should appear on the other ComApp window.
2.5 Extended Baud Rate O peration
Though it isn’t possible to set baud rates greater than 115.2 kbaud on the PCI-COM series using the
standard Windows Communications Port Properties dialog, the board and operating system are actually
capable of operating at transfer rates up to 460.8 kbaud. The PCI-COM series boards have a
programmable divider between the on-board system clock and the UART. This divider can be set using
the Advanced tab that was added to the Windows 95/98 Communications Port Properties dialog, or the
PCIcom applet added to the NT/2000 Control Panel during the PCI-COM software installation.
If the divider is set to divide-by-4 (the default setting) the board’s baud rate is exactly as Windows sets it.
If the divider is set to divide by two, all the actual board baud rates become double what Windows has set
them to, while 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. We have only shown the values for the
baud rates higher than normally supported by windows.
UART Windows baud Actual
Clock Rate Divider rate setting baud rate
1.8432 MHz 4 (default) 115.2 kbaud 115.2 kbaud
3.6864 MHz 2 115.2 kbaud 230.4 kbaud
7.3728 MHz 1 115.2 kbaud 460.8 kbaud