Connect Tech Titan/cPCI - Manual (Page 25)

Titan/cPCI User’s Manual, Connect Tech Inc.
20 Revision 1.01
Full Duplex Mode (4 wire)
By not installing pins on jumper block JA and by using features in our driver software, you can
run the individual RS-422/485 ports in full duplex mode. This mode is typically used in point to
point RS-422/485 situations much like RS-232. In this mode, TxD & RxD are active all the
time.
Figure 1 shows the location of jumper block JA.
Half Duplex RS-422/485 (2 wire)
By installing pins on jumper block JA and using features in our driver software, you can run the
individual RS-422/485 ports in half duplex mode. In this mode your Titan/cPCI adapter controls
the transmitter and receiver circuits. DTR is turned on prior to and during transmission to cause
the transmit driver to enable and the receiver to disable. DTR is turned off when not
transmitting to cause the transmit driver to disable (tri-stated) and the receiver to enable. The
16C950 UARTs on the Titan/cPCI adapter are responsible for timing the DTR toggle.
Multi-drop Slave Mode (4 wire)
By not installing jumpers on jumper block JA and by using features in our driver software, you
can run the individual RS-422/485 ports in multi-drop slave 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.
Example
The example below shows the settings on JA where RS-422/485
ports 1 and 2 are set for full duplex or multi-drop slave mode,
port 3 is set for half duplex and port 4 is not set since port 4 is
set for RS-232 on jumper block JB.
JA
Jumper Legend
Jumpers on = ½ duplex
enabled
Port 1
Port 2
Port 3
Port 4
4 port models
JA0
JA1
JA2
JA3
Technical Note:
Full duplex, multi-drop slave and half duplex modes apply to
RS-422/485 ports only. Please ensure that the port is set for
RS-422/485 on jumper block JB.