Connect Tech BlueStorm/Express User Manual
Revision 0.15
14
Half Duplex Mode
In this mode the TxD+/- line driver is enabled only when data is transmitted and RxD+/- is
disabled when data is being transmitted. This mode is typically used in either point-to-point 2-wire
connections OR in multi-drop 2-wire bus connections. This mode requires software setup in
Control Panel
–
System
–
Hardware
–
Device Manager
–
Ports
–
CTI PCI Express UART.
Click on
Advanced
under
Port Settings
after the driver is installed. (See
Port Settings
).
Multi-drop Mode
In this mode the TxD+/- line driver is enabled only when data is transmitted and RxD+/- is
enabled all the time. This mode is typically used in multi-drop 4-wire connections. This mode
requires software setup in
Control Panel
–
System Properties
–
Hardware
–
Device Manager
–
Ports
–
CTI PCI Express UART
. Click on
Advanced
under
Port Settings
. (See Half Duplex Mode above.)
Line Bias/Termination
The RS-422/485 transceivers transmit and receive, are optionally biased to produce a line level
mark condition through jumper selectable resistors. These options are typically used in multi-drop
4-wire connections.
Jumper Block Settings
The following jumper block diagram depicts typical settings on a four-port selectable
BlueStorm/Express. Jumper blocks JA and JB control ports 1 and 2, JC and JD control ports 3 and
4, respectively. (See
Figures 1 to 7
for location of jumper blocks.)
Figure 8: Example of various port configuration jumper block settings
In this example, Port 1(JA) is set to RS-232, Port 2 (JB) is set to RS-422/485
half duplex, Port 3 (JC) is set to RS-422/485 full duplex, and Port 4 (JD) is set
to RS-422/485 multi-drop.
RS-485 Selection
: Install this jumper to configure a port for RS-422/485 mode. If the jumper is
not installed, the port will function in RS-232 mode. (All jumpers should be removed from any
port operating in RS-232 mode.)
TxD Control
: Install this jumper to enable the RS-485 transmitter only when sending data. This
mode is useful for half-duplex operation when only one device is allowed to send data at a time. If
the jumper is not installed, the transmitter will always drive the line to an idle state when not
sending data.
RxD control
: Install this jumper to enable the RS-485 receiver only when NOT transmitting data.
This is useful for half-duplex operation to prevent the transmitting device from receiving the data
it has sent. If this jumper is not installed, the receiver is always enabled and ready to receive data.
RxD ± Termination/Bias
: Install this pair of jumpers to enable a 150 Ohm terminator across the
RxD+ and RxD- pins for the corresponding port. A biasing network is also enabled that drives the
receiver to an inactive or safe mode. The receiver can still receive data from another device and
the biasing helps to prevent the reception of data generated by noise on the transmission line. The
two jumpers for RxD termination/bias must be installed and removed as a pair.