Danfoss VLT AutomationDrive FC 360 Design Manual

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Danfoss VLT AutomationDrive FC 360 Design Manual Manual pdf 70 page image

5.8.6 Data FieldThe data field is constructed using sets of 2 hexadecimaldigits, in the range of 00 to FF hexadecimal. These aremade up of one RTU character. The data field of messagessent from a master to slave device contains additionalinformation which the slave must use to take the actiondefined by the function code. This can include items suchas coil or register addresses, the quantity of items to behandled, and the count of actual data bytes in the field.5.8.7 CRC Check FieldMessages include an error-checking field, operating basedon a cyclical redundancy check (CRC) method. The CRCfield checks the contents of the entire message. It isapplied regardless of any parity check method used for theindividual characters of the message. The CRC value iscalculated by the transmitting device, which appends theCRC as the last field in the message. The receiving devicerecalculates a CRC during receipt of the message andcompares the calculated value to the actual value receivedin the CRC field. If the 2 values are unequal, a bus time-outresults. The error-checking field contains a 16-bit binaryvalue implemented as 2 8-bit bytes. When this is done, thelow-order byte of the field is appended first, followed bythe high-order byte. The CRC high-order byte is the lastbyte sent in the message.5.8.8 Coil Register AddressingIn Modbus, all data is organised in coils and holdingregisters. Coils hold a single bit, whereas holding registershold a 2-byte word (that is 16 bits). All data addresses inModbus messages are referenced to 0. The first occurrenceof a data item is addressed as item number 0. Forexample: The coil known as ‘coil 1’ in a programmablecontroller is addressed as coil 0000 in the data addressfield of a Modbus message. Coil 127 decimal is addressedas coil 007Ehex (126 decimal).Holding register 40001 is addressed as register 0000 in thedata address field of the message. The function code fieldalready specifies a ‘holding register’ operation. Therefore,the ‘4XXXX’ reference is implicit. Holding register 40108 isaddressed as register 006Bhex (107 decimal).CoilNumberDescription Signal Direction1-16 Frequency converter control word(see Table 5.16)Master to slave17-32 Frequency converter speed or set-point reference Range 0x0–0xFFFF(-200% ... ~200%)Master to slave33-48 Frequency converter status word(see Table 5.17 )Slave to master49-64 Open loop mode: Frequencyconverter output frequencyClosed loop mode: Frequencyconverter feedback signalSlave to master65 Parameter write control (master toslave)Master to slave0=Parameter changes are writtento the RAM of the frequencyconverter1=Parameter changes are writtento the RAM and EEPROM of thefrequency converter.66-65536 ReservedTable 5.15 Coil RegisterCoil 0 101 Preset reference LSB02 Preset reference MSB03 DC brake No DC brake04 Coast stop No coast stop05 Quick stop No quick stop06 Freeze frequency No freeze frequency07 Ramp stop Start08 No reset Reset09 No jog Jog10 Ramp 1 Ramp 211 Data not valid Data valid12 Relay 1 off Relay 1 on13 Relay 2 off Relay 2 on14 Set up LSB1516 No reversing ReversingTable 5.16 Frequency Converter Control Word (FC Profile)RS485 Installation and Set-... Design Guide68 Danfoss A/S © 09/2014 All rights reserved. MG06B40255