19
Drawing No. LP1106
Chapter 4 Communications Connections
Revision B
Communication Ports
ST-IPm-8460
SixTRAK IPm
®
RTU/Controller
Chapter 4 Communications Connections
Communication Ports
The Red Lion SixTRAK IPm
RTU/Controller covered by this manual has various combinations of Ethernet and serial ports
as shown in Table 4.1 below.
Table 4.1
PRODUCT
USB
PORT
RS232
PORT A
RS232
PORT B
RS485
PORT C
RS232
PORT D
ETHERNET
PORT 1
ETHERNET
PORT 2
BUILT-IN
SWITCH
ST-IPM-8460
X
X
X
X
X
X
X
X
RS232 Ports A & B
These ports are identical in connection and functionality. A RJ45 female connector is provided for each. The pin-outs
follow the EIA/TIA-561 standard. A pre-wired DB9F to RJ45F adapter is included with these units. Use this adapter along
with a RJ45 male to RJ45 male straight-thru wired patch cable (not included) to make a connection between a com port
on your PC (DB9 male) and either Port A or B (RJ45 female). Refer to the Red Lion Electronic catalog for more information
on connecting to other equipment.
RJ45 Pin Locations (for RS232 or Ethernet):
RS485 Port C
This port is found on all units. It provides a RS485 (2-wire, half duplex only) connection to Red Lion’s EtherTRAK-2 I/O
modules or other equipment. Three terminals (for signal gnd, 485+, and 485-) are provided. Generally, you c to +
and - to - between units. However, since there is no standard for RS485 terminal designations you may need to c
to - and - to + in some cases. No damage will result if you connect incorrectly. It is highly recommended that you tie the
signal ground to an appropriate ground (if available) between all RS485 units. Make sure to use a good quality communication
cable with three conductors (twisted is preferred) plus a shield. To prevent ground loops, the shield should be connected
to chassis ground on only one end of any cable run.
Note:
If you have existing wiring that has only two conductors and a shield, you can use the shield to connect the signal
grounds between stations. This is not optimal (especially for long cable runs) but should work in most situations.
RS485 Termination:
RS485 Termination is achieved through software configuration. In the port C configuration check
the RS-485 Termination check box. Once the configuration is loaded to the SixTRAK IPm RTU/Controller the termination
will take affect (150 ohm and a 0.1 µF capacitor connected in series). It is recommended that both end stations of your
RS485 network be terminated. Avoid terminating more than two stations. Refer to the EtherTRAK-2 I/O modules User
Manual on how to terminate an EtherTRAK-2 module. For 3rd party devices, please refer to their user manual for
termination instructions. Red Lion manuals can be found on the Red Lion website.
Bias Resistors:
On a RS485 2-wire network, a pair of bias resistors (1K ohm typically) acting upon the transmit/receive
wires may be required. If bias resistors are not present, the receive inputs on some RS485 devices may react to noise on
the floating wires. The bias resistors will force the transmit/receive wires to a known (non-floating) state when none of the
RS485 devices are transmitting data. Some RS485 devices have bias resistors built-in, and are enabled through DIP-switch
or jumper settings. Make sure there is only one pair of bias resistors acting upon the network.
Note:
If your RS485 network is made up exclusively of Red Lion devices, then these bias resistors are not necessary.