10.3 Bus TerminationThe RS-485 bus must be terminated by using a resistornetwork at both ends. For this purpose, set switch S801 onthe control card to "ON". For more information, seechapter 7.5.4 Switches S201 (A53), S202 (A54), and S801.Communication protocol must be set to 8-30 Protocol.10.4 RS-485 Installation and Set-up10.4.1 EMC PrecautionsTo achieve interference-free operation of the RS-485network, the following EMC precautions are recommended.Relevant national and local regulations, regardingprotective ground connection, for example, must beobserved. The RS-485 communication cable must be keptaway from motor and brake resistor cables to avoidcoupling of high-frequency noise from one cable toanother. Normally a distance of 200 mm (8 in) is sufficient.However, in situations where cables run in parallel overlong distances, keeping the greatest possible distancebetween cables is recommended. When crossing isunavoidable, the RS-485 cable must cross motor and brakeresistor cables at an angle of 90°.Serial com. bus cableBrake resistorMin. 200mm90° crossing130BA080.10Figure 10.3 EMC Precautions10.5 FC Protocol OverviewThe FC protocol, also referred to as FC bus or Standardbus, is the Danfoss standard serial communication bus. Itdefines an access technique according to the master/follower principle for communications via a serial bus.One master and a maximum of 126 followers can beconnected to the bus. The master selects the individualfollowers via an address character in the message. Afollower itself can never transmit without first beingrequested to do so, and direct message transfer betweenthe individual followers is not possible. Communicationsoccur in the half-duplex mode.The master function cannot be transferred to another node(single-master system).The physical layer is RS-485, thus utilizing the RS-485 portbuilt into the adjustable frequency drive. The FC protocolsupports different message formats:• A short format of 8 bytes for process data• A long format of 16 bytes that also includes aparameter channel• A format used for texts10.6 Network Configuration10.6.1 Adjustable Frequency Drive Set-upSet the following parameters to enable the FC protocol forthe adjustable frequency drive.Parameter number Setting8-30 Protocol FC8-31 Address 1–1268-32 FC Port BaudRate2400–1152008-33 Parity / Stop Bits Even parity, 1 stop bit (default)Table 10.2 FC Protocol ParametersRS-485 Installation and Set... Design Guide268 Danfoss A/S © Rev. 2014-02-10 All rights reserved. MG34S2221010
