Danfoss VLT AutomationDrive FC 300 Operating Instructions Manual

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Danfoss VLT AutomationDrive FC 300 Operating Instructions Manual Manual pdf 134 page image

7.1.2 EMC PrecautionsThe following EMC precautions are recommended in orderto achieve interference-free operation of the RS-485network.Relevant national and local regulations, for exampleregarding protective earth connection, must be observed.The RS-485 communication cable must be kept away frommotor and brake resistor cables to avoid coupling of highfrequency noise from one cable to another. Normally adistance of 200 mm (8 inches) is sufficient, but keeping thegreatest possible distance between the cables is generallyrecommended, especially where cables run in parallel overlong distances. When crossing is unavoidable, the RS-485cable must cross motor and brake resistor cables at anangle of 90 degrees.Fieldbus cableMin.200mm90° crossing130BA080.11Illustration 7.3The FC protocol, also referred to as FC bus or Standardbus, is the Danfoss standard fieldbus. It defines an accesstechnique according to the master-slave principle forcommunications via a serial bus.One master and a maximum of 126 slaves can beconnected to the bus. The master selects the individualslaves via an address character in the telegram. A slaveitself can never transmit without first being requested todo so, and direct message transfer between the individualslaves is not possible. Communications occur 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 frequency converter. The FC protocolsupports different telegram 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 texts.7.2 Network Configuration7.2.1 Set-upSet the following parameters to enable the FC protocol forthe frequency converter.Parameter Number Setting8-30 Protocol FC8-31 Address 1 - 1268-32 FC Port Baud Rate 2400 - 1152008-33 Parity / Stop Bits Even parity, 1 stop bit (default)Table 7.27.3 FC Protocol Message Framing Structure7.3.1 Content of a Character (byte)Each character transferred begins with a start bit. Then 8data bits are transferred, corresponding to a byte. Eachcharacter is secured via a parity bit. This bit is set at "1"when it reaches parity. Parity is when there is an equalnumber of 1s in the 8 data bits and the parity bit in total.A stop bit completes a character, thus consisting of 11 bitsin all.0 1 32 4 5 6 7195NA036.10StartbitEven StopParity bitIllustration 7.47.3.2 Telegram StructureEach telegram has the following structure:1. Start character (STX)=02 Hex2. A byte denoting the telegram length (LGE)3. A byte denoting the frequency converter address(ADR)RS-485 Installation and Set... VLT Automation Low Harmonic Drive Operating InstructionsMG34O202 - VLT® is a registered Danfoss trademark 1337 7