Danfoss VT2800 Series Design Manual

Contents

VLT ® 2800 SeriesDescription of choice:Select the required control word protocol.For further information about using the Metasys N2Protocol see MG91CX and Modbus RTU see MG10SX.570 Modbus parity and message framing(M.BUS PAR./FRAME)Value:(EVEN/1 STOPBIT) [0](ODD/1 STOPBIT) [1]✭ (NO PARITY/1 STOPBIT) [2](NO PARITY/2 STOPBIT) [3]Function:This parameter sets up the drive’s Modbus RTUinterface to communicate properly with the mastercontroller. The parity (EVEN, ODD, or NO PARITY) mustbe set to match the setting of the master controller.Description of choice:Select the parity that matches the setting for theModbus master controller. Even or odd parity issometimes used to allow a transmitted word to bechecked for errors. Because Modbus RTU usesthe more efficient CRC (Cyclic Redundancy Check)method of checking for errors, parity checking isseldom used in Modbus RTU networks.571 Modbus communications timeout(M.BUS COM.TIME.)Value:10 ms - 2000 ms ✭ 100 msFunction:This parameter determines the maximum amountof time that the drive’s Modbus RTU will waitbetween characters that are sent by the mastercontroller. When this amount of time expires, thedrive’s Modbus RTU interface will assume that ithas received the entire message.Description of choice:Generally, the value of 100 ms is sufficient for ModbusRTU networks, although some Modbus RTU networksmay operate on a timeout value as short as 35 ms.If this value is set too short, the drive’s Modbus RTUinterface may miss a part of the message. Since theCRC check will not be valid, the drive will ignore themessage. The resulting retransmissions of messageswill slow communications on the network.If this value is set too long, the drive will wait longerthan necessary to determine that the message iscompleted. This will delay the drive’s response to themessage and possibly cause the master controller totime out. The resulting retransmissions of messageswill slow communications on the network.580-582 Defined parameters(DEFINED PNU’S)Value:Read onlyFunction:The three parameters hold a list of all the parametersthat are defined in the VLT 2800. It is possible to readsingle elements of the list by using the correspondingsubindex. The subindexes start at 1 and followthe order of the parameter numbers.Each parameter holds up to 116 elements(parameter numbers).When a 0 is returned as parameter number the list ends.✭ = factory setting. () = display text [] = value for use in communication via serial communication portMG.28.E9.02 - VLT is a registered Danfoss trademark126