Danfoss VT2800 Series Design Manual

Contents

VLT ® 2800 SeriesProgrammingTelegram length (LGE)The telegram length is the number of data bytes plusthe address byte ADR plus 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+n bytes.10 represents the fixed characters, while the ’n’ isvariable (depending on the length of the text).Frequency converter address (ADR)Two different address formats are used, withthe frequency converter’s address range beingeither 1-31 or 1-126.1. Address format 1-31The byte for address range 1-31 has thefollowing profile:Bit 7 = 0 (address format 1-31 active)Bit 6 is not usedBit 5 = 1: Broadcast, address bits (0-4) are not usedBit 5 = 0: No BroadcastBit 0-4 = Frequency converter address 1-312. Address format 1-126The byte for address range 1 - 126 hasthe following profile:Bit 7 = 1 (address format 1-126 active)Bit 0-6 = Frequency converter address 1-126Bit 0-6 = 0 BroadcastThe slave sends the address byte back unchangedin the response telegram to the master.Example:writing to frequency converter address 22 (16H)with address format 1-31:Data control byte (BCC)The data control byte is explained in this example:Before the first byte in the telegram is received,the Calculated CheckSum (BCS) is 0.When the first byte (02H) has been received:BCS = BCC EXOR "first byte"(EXOR = exclusive-or)BCS = 0 0 0 0 0 0 0 0 (00 H)EXOR1. byte = 0 0 0 0 0 0 1 0 (02H)BCC = 0 0 0 0 0 0 1 0 (02H)Each subsequent byte gates with BCS EXORand produces a new BCC, e.g.:BCS = 0 0 0 0 0 0 1 0 (02H)EXOR2nd byte = 1 1 0 1 0 1 1 0 (D6H)BCC = 1 1 0 1 0 1 0 0 (D4H)MG.28.E9.02 - VLT is a registered Danfoss trademark 109