Danfoss VLT HVAC Design Manual

Also see for VLT HVAC: Instructions Operating instructions Instruction Operating instructions Instruction manual

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Danfoss VLT HVAC Design Manual Manual pdf 132 page image

ParameterNumberParameterNameSetting8-30 Protocol FC8-31 Address 1 - 1268-32 Baud Rate 2400 - 1152008-33 Parity/StopbitsEven parity, 1 stop bit (default)7.4 FC Protocol Message Framing Structure7.4.1 Content of a Character (byte)Each character transferred begins with a start bit. Then 8 data bits are transferred, corresponding to a byte. Each character is secured via a parity bit,which is set at "1" when it reaches parity (i.e. when there is an equal number of 1’s in the 8 data bits and the parity bit in total). A character is completedby a stop bit, thus consisting of 11 bits in all.7.4.2 Telegram StructureEach telegram begins with a start character (STX)=02 Hex, followed by a byte denoting the telegram length (LGE) and a byte denoting the frequencyconverter address (ADR). A number of data bytes (variable, depending on the type of telegram) follows. The telegram is completed by a data controlbyte (BCC).7.4.3 Telegram Length (LGE)The telegram length is the number of data bytes plus the address byte ADR and the data control byte BCC.The length of telegrams with 4 data bytes is LGE = 4 + 1 + 1 = 6 bytesThe length of telegrams with 12 data bytes is LGE = 12 + 1 + 1 = 14 bytesThe length of telegrams containing texts is 10 1)+n bytes1) The 10 represents the fixed characters, while the “n’” is variable (depending on the length of the text).7.4.4 Frequency Converter Address (ADR)Two different address formats are used.The address range of the frequency converter is either 1-31 or 1-126.7 RS-485 Installation and Set-up VLT® HVAC Drive Design Guide132 MG.11.B9.02 - VLT® is a registered Danfoss trademark7