Cabling a Linx Rs485 (Serial) Network
CABLING A LINX RS485 (SERIAL) NETWORK
USING THE LINXNET CONNECTOR
OVERVIEW
A LINX RS485 (Serial) network consists of five components: a host computer, more than 1 LINX terminal, RS485 cables, RS232 or RS422 cables, and connectors.
The Host:
There is no standard host computer. For more information see the LINX User’s Manual.
The LINX:
There are up to seven network roles in a LINX network; Master, Alt-Master, Concentrator, Sub-Master, Alt-SubMaster, Normal, and Gateway. At installation, each LINX should be configured for its network role. This configuration is made through the network menu on each individual LINX unit. See the LINX User’s Manual for more information.
LINX Network Cabling:
Generally speaking, the cables that run to and from LINX/host com ports are RS232 or RS422 cables. This is dependent on whether the com ports on the host and the terminals are RS232 or RS422. The cables that connect individual LINX’s together via the network connector are RS485.
Since the RS485 connections are a simple daisy-chain system, the LINXNet connector can help simplify large network configurations. The information in the following sections is designed to help setup your LINX network using the LINXNet connector.
USING THE LINXNET CONNECTOR
Tools Needed:
You will need a 3/32” flat-blade screwdriver, and a pair of wire strippers/cutter.
Cable Wire:
The recommended cable is the stranded twisted pair with an overall shield and drain wire with either 22 gauge or 24 gauge wire. The most popular cable is a Belden 9462 or equivalent.
Preparing the Wire:
Check that the cable is cut off evenly. (There should be no wire hanging beyond the cable insulation.) Remove about ¾” of the insulation and grounding shield from the end of the cable. Strip about ¼” of insulation from the end of each wire.
Inspecting the Connector:
Remove the hood from the LINXNet connector. You will see a four-screw terminal block installed on the back of the connector. The black terminal is network (-), the red terminal is network (+), the blue terminal is the LINX’s chassis ground, and the fourth terminal is the network shield wire. (See Appendix A for a pinout diagram)
LinxNet Connections:
There are two types of LINXNet connections: A master connection and a non-master connection. For a non-master connection the network shield wire is placed in the LinxNet connector’s fourth terminal. For a master connection the network shield wire is placed in the LINX’s chassis ground terminal (the blue terminal). On any network daisy-chain there should be only one master connection. (The master connection is usually put on the master or sub-master.) The following diagram demonstrates the wiring of a RS-485 network using the LINXNet connector.
Installing the Connector:
In the LINXNet connector the three wires connecting the terminal block to the pins in the DB9 are color coded. This is consistent with all LINXNet connectors. It is advised that you color-code your cable to match the LINXNet to avoid confusion.
If two wires are to be installed in one terminal twist them together. Place the network (-) wires in the black terminal, place the network (+) wires in the red terminal, and place the shield wires in one of the remaining terminals according to the LINXNet connection required (Master or Normal terminal). The terminals should then be screwed tightly down and the wires inspected to insure that they cannot short together.
If you have cut and stripped your cable according to the instructions above, you should now be able to put the hood on the LINXNet connector. It is advised that you take advantage of the cable restraint device in the connector to avoid shorting or breaking the wire. Remember, cabling problems are the number one cause of problems with your network.
LINX NETWORK CABLING
The RS232 or RS422 Cables:
An RS232 or RS422 cable is a point-to-point cable. It connects only two units; either HOST to LINX MASTER/GATEWAY or CONCENTRATOR to SUBMASTER. You can use standard null modem cables for most RS232 applications. A CONCENTRATOR to SUB-MASTER cable requires a standard null modem cable terminated with two FEMALE DB9 connectors.
There are only four RS232/422 cable configurations for the LINX. They are RS422, RS232 null modem, RS232 modem, and the RS232 DSR configurations. See appendix A for pin-out diagrams of these cables.
The RS485 Cables:
The RS485 (network) cable is a daisy-chain system. Each LINX is directly connected to only one or two other LINXes.
The RS485 network uses standard 9-pin D-shell male connectors (DB9). You may wire these connectors yourself or use the LINXNet connectors which are designed for the LINX network.
Running Power Through the Network
The LINXNet connector does not allow power to be supplied on the network. If your LINXIII will be powered through the network cable then you need to use standard DB9’s. For more information see the LINX Installation Manual.
The Terminator Switch
After the network is installed it is necessary to cancel out signal reflections inherent in any cable layout. To do this, flip on the terminator switch underneath the MASTER LINX.
The Terminator Switch
APPENDIX A
NETWORK PIN-OUT DIAGRAMS
The following diagrams represent a list of possible RS232/RS-422 connections using DB9-pin and DB25-pin connectors.
RS232 Linx/Host 25-pin Null-Modem RS232 Linx/Host 9-Pin Null-Modem
RS232 Linx/Host 25-Pin Modem RS232 Linx/Host 25-Pin DSR Control
LINX NETWORK PIN-OUT DIAGRAMS CONTINUED
RS232 Linx/Host 9-Pin DSR Control RS232 Concentrator/Submaster
RS422 Concentrator/Submaster RS422 Linx/Any Host Connector
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