Setting Driver Options
42
Chapter 4
Manual Documentation Number 3PCIoUx-1008
UART will request that the computer transfer the contents of the buffer to
program memory. This is intended to optimize the throughput of the data.
The default value is 14. Usually this parameter does not have to be changed.
Setting the RTS Control Parameter
1.
Set
RTS Control
to
Normal
for RS-232; set
RTS Control
to
RS-
485 Mode
for 2-wire or 4-wire RS-485 operation. Either setting can
be used for RS-422.
Typically the COM parameters set in this dialog box are overridden
by the software application.
Note: For proper operation the DIP switches on the PCI card must be
set for the same mode. Refer to Chapter 2 for more information on
configuring the DIP switches.
2.
The
Direction control delay (bit times)
box allows you to set the
length of time the Transmit driver continues to be enabled after the
last bit of data in the transmit register has been sent. The purpose of
this setting is to maintain the transmission line in a know (idle) state
until the data has reached its destination. If the line is released too
soon it can pick up noise that could cause problems on the
communications system. This parameter is preset to a value of 10
bit times and typically will not have to be changed. For longer
transmission lines this value may have to be increased.
Setting the Hardware Handshaking Level
The
Hardware handshaking Hysteresis level (characters)
parameter
allows you to set how long the local UART will continue to accept data after
its receive buffer has reached the point at which it asks the computer to
transfer the data to program memory. When this point is reached the UART
de-asserts the RTS hardware handshake line (which is connected to the
remote UART’s CTS line), stopping the remote device from sending data
until its CTS line is re-asserted. This will occur when the local receive FIFO
buffer has been cleared. The default value for this parameter is 0. Typically
this value will not need to be changed.
Changing the COM Port Name/Number
1.
To change the COM port number assigned to the port, click the
COM Port Name
arrow and select the new
COM Port Name
from
the list.
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