Networking Options

The standard FAC-2100 provides hardware support for networks compatible with RS-232, RS-422, and RS-485 voltage levels.

RS-232 point-to-point serial networks in the FAC-2100 are used to provide an interface between a maximum of two devices (typically between a personal computer and a FAC-2100 controller). Programming the controller is normally accomplished through this interface. This network can be used to transmit data at a maximum of 57,600 bits per second over a maximum distance of about 49 feet.

RS-422 and RS-485 multi-drop serial networks can connect up to 32 'unit load' devices via a three-wire link (note: more then 32 unit load devices can be connected by using a network repeater/isolator – contact Fairmount Automation for more information.) Each FAC-2100 is 1/8 a unit load so up to 256 FAC-2100s can be networked.

The network contains one master that initiates all communications. Each remaining slave device on the link will respond only when the master device attempts communication with it. This network can be used to transmit information at 115,200 bits per second over a maximum distance of 4000 feet (the network distance can be increase by using a network repeater/isolator.)

Care should be taken when selecting the wire type to be used for the transmission channel. For short distances (typically under 10 feet), standard 22 to 24 AWG twisted pair telephone cable can be utilized. If the network extends over larger distances, higher quality wire should be used (such as Datalene (type 8162) wire from Belden Wire and Cable Company). Note: Cat 5 Ethernet communications cable is an acceptable alternative.

RS-485 networks should be wired in a straight-line bus with biasing and terminated at the two ends. Termination resistors should match the characteristic impedance of the transmission line (typically 120 ohms). Note that the FAC-2100 has internal dip switches that can activate built-in 120 ohm termination resistors.

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