Danfoss VLT FC 102 Series Design Manual

Also see for VLT HVAC Drive FC 102: Operating instructions Service guide Programming guide Installation guide Installation guide

Contents

8.9 How to Access Parameters8.9.1 Parameter HandlingThe PNU (Parameter Number) is translated from theregister address contained in the Modbus read or writemessage. The parameter number is translated to Modbusas (10 x parameter number) DECIMAL. Example: Reading3-12 Catch up/slow-down value (16 bit): The holdingregister 3120 holds the parameters value. A value of 1352(Decimal) means that the parameter is set to 12.52%.Reading 3-14 Preset Relative Reference (32 bit): The holdingregisters 3410 and 3411 hold the parameters value.A value of 11300 (decimal), means that the parameter isset to 1113.00 S.For information on the parameters, size and convertingindex, consult the product relevant programming guide.8.9.2 Storage of DataThe Coil 65 decimal determines whether data written tothe adjustable frequency drive are stored in EEPROM andRAM (coil 65=1) or only in RAM (coil 65=0).8.9.3 INDSome parameters in the adjustable frequency drive arearray parameters, e.g., 3-10 Preset Reference. Since theModbus does not support arrays in the holding registers,the adjustable frequency drive has reserved the holdingregister 9 as pointer to the array. Before reading or writingan array parameter, set the holding register 9. Settingholding register to the value of 2, causes all followingread/write to array parameters to be to the index 2.8.9.4 Text BlocksParameters stored as text strings are accessed in the sameway as the other parameters. The maximum text block sizeis 20 characters. If a read request for a parameter is formore characters than the parameter stores, the response istruncated. If the read request for a parameter is for fewercharacters than the parameter stores, the response ispadded with spaces.8.9.5 Conversion FactorThe different attributes for each parameter can be seen inthe section on factory settings. Since a parameter valuecan only be transferred as a whole number, a conversionfactor must be used to transfer decimals.8.9.6 Parameter ValuesStandard data typesStandard data types are int 16, int 32, uint 8, uint 16 anduint 32. They are stored as 4x registers (40001–4FFFF). Theparameters are read using function 03HEX "Read HoldingRegisters." Parameters are written using the function 6HEX"Preset Single Register" for 1 register (16 bits), and thefunction 10 HEX "Preset Multiple Registers" for 2 registers(32 bits). Readable sizes range from one register (16 bits)up to ten registers (20 characters).Non-standard data typesNon-standard data types are text strings and are stored as4x registers (40001–4FFFF). The parameters are read usingfunction 03HEX "Read Holding Registers" and written usingfunction 10HEX "Preset Multiple Registers." Readable sizesrange from one register (two characters) up to tenregisters (20 characters).8.10 ExamplesThe following examples illustrate various Modbus RTUcommands.8.10.1 Read Coil Status (01 HEX)DescriptionThis function reads the ON/OFF status of discrete outputs(coils) in the adjustable frequency drive. Broadcast is neversupported for reads.QueryThe query message specifies the starting coil and quantityof coils to be read. Coil addresses start at zero, that is,coil 33 is addressed as 32.Installation and Set-up Design GuideMG11BC22 Danfoss A/S © Rev. 06/2014 All rights reserved. 1598 8