RS-422/485 Multiport Serial PCI Card
15
7. Set
High
Baud
Rate
The RS-422/485 card was shipped at the low baud rate
(115.2Kbps maximum). To set to high baud rate to 921.6Kbps
maximum, 2 steps are required:
Change the UART input clock jumper (JP5) to
“HI”
Go to the COM port’s settings of Windows’ Device
Manager to let it detect the clock speed automatically
7.1 Windows
2000,
XP
Set the JP5 to “HI”
In the Windows COM port properties as the following figure,
select
〝
Data rate
〞
and click on
〝
Detect Crystal
Frequency
〞
The
〝
Crystal Frequency
〞
settings will be set to
〝
14.7456MHZ
〝
, then click
〝
OK
〞
The settings will be saved by Windows. You don’t need to
configure it again whenever you restart the system
RS-422/485 Multiport Serial PCI Card
4
3.1.2 JP1: RS-422/485 Mode Selector
Mode Settings for both S1 and S2 (JP1):
Jumper Name
Jumper Positions
Mode and Termination Resistor
Setting
485
(Default)
2-wire RS-485 mode
485/422
422 4-wire
RS-422
mode
RTS
RS-485 Transmitter Buffer Enable is
Controlled by RTS (active high)
RTS/AUTO
AUTO
(Default)
RS-485 Transmitter Buffer is
controlled automatically by ATTA
TM
hardware circuit
ECHO Transmitting
data
will
be
echoed
back
ECHO/NO_ECHO
NO_ECHO
(Default)
No echo data
LOOP
RTS will be connected to CTS
LOOP/NO_LOOP
NO_LOOP
(Default)
RTS and CTS operate normally
Please note that if the mode were set at “422” mode, the
other settings (AUTO, ECHO and LOOP settings) will take no
effect.
The Echo mode is useful for the application program to
detect if the RS-485 bus were in a collision. If the echoed
data was not equal to the transmitted data, then the bus
was in a collision.
If you want to set the RS-485 transceiver to “AUTO” mode,
you have to go to Windows Device Manager to turn on
this option as well. You only need to do it once and the
Windows will keep the settings afterward. Please note that
422
AUTO
NO_ECHO
NO_LOOP
485
RTS
ECHO
LOOP
