Networking
Network Port Settings
The FAC-2100 supports RS-485 or RS-422 network communications. Selection of the physical network type, termination, and biasing options are set via dip-switch type jumpers internal to the unit.
Remove the side cover of the FAC-2100 (item 22 in the Parts List Exploded View) to gain access to the board with the dip-switches. The board with the dip switches is the Microprocessor and I/O Board (item 29 in the Parts List Exploded View). See the figure below for an image of the surface of the Microprocessor and I/O Board in the vicinity of the switches. Note that adjacent to the switch are labels for the switch function as well as an indicator for the direction of the ON and OFF positions.
Network Configuration Dip-Switches on Microprocessor and I/O Board
The switches have the following function:
SW485 Switch
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For RS-485 mode, keep all of SW422 switches in the OFF position (to the right). On two controllers in the network, activate the network biasing by setting their RS-485 bias resistors in the ON position (to the left). All the other controller in the network should have these switches in the OFF position (to the right). The controllers on each end of the bus should have their termination resistors set ON (to the left) or use external 120 ohm terminators.
Example RS-485 Network Cabling Topology
The figure above shows a typical RS-485 network. Note the following In this example:
- The cable topology is that of a straight-line bus.
- The controllers on the end of the bus have their termination switches activated.
- Two controllers on the network (doesn't matter which two) have their bias switches activated.
- Stubs (the cable length between the 'T' connection in the bus and the controller) are kept as short as possible. Ideally, there are no stubs and the wiring simply chains from controller to controller.
Example RS-485 Network Wiring
The above figure shows another example of RS-485 network wiring. In this case the network cabling goes from the COM 1 connecter of one controller to the COM 2 connector of the next controller in the bus. An alternative approach (which leaves the COM 1 connector open for connection to a configuration PC) is to go from COM 2 to COM 2 and splice the connections in the circular connector.
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The following diagram shows the configuration:
Example RS-422 Network Connections
It is important to make sure that the twisted pair wires are connected to the RS-422 +/- pairs. In the diagram above, the tan and green lines each represent a twisted pair communication channel.
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The tan twisted pair represents the second channel on the bus. For the tan channel, activate the termination resistor on the slave at the remaining end of the bus (slave station n in the diagram below). At least one slave station must have its biasing resistors activated. For redundancy it is recommended to active two slave station RS-422 biasing (no more then two should be activated).
RS-422 Network Topology
For RS-422 mode, place the RS-422 ON/RS-485 OFF switch to the ON position (to the left).
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In all cases, the RS-485 Bias Resistors should both be set to the OFF position (to the right).