Frequency Inverter DF51... - Moeller.com.tr

Serial interface (Modbus)04/07 AWB8230-1541GBThe network protocolTransmissionTransmission takes place in RTU mode. The message contains noheader or end characters and conforms to the following syntax:Slave address Task Data CRC-16Figure 160: RTU modeCRC-16: Block parity test character (cyclic redundancy check)The data is transmitted in binary code. The end of the telegram isrecognized by a pause in transmission of at least 3.5 characters(latency).The data transmission between a PLC and the frequency inverter(DF51) has the following pattern:• Request – the PLC sends a protocol (Modbus) frame to thefrequency inverter.• Response – after the cyclic waiting time defined by the system(plus the time in PNU C078), the frequency inverter respondswith a protocol (Modbus) frame to the PLC.hThe frequency inverter (slave) sends a response only if ithas previously received a request from the master.The protocol (Modbus) frame has the following structure:• Header (non-operative mode)• Slave address• Function code• Data• Error check• Trailer (non-operative mode)Structure of requestSlave address:• Here the slave address (1 to 32) of the recipient frequencyinverter is entered. Only the frequency inverter with this addresscan respond to the request.• Slave address 0 is used for broadcasting (sending a message toall bus stations). In this mode no single station can beaddressed and slaves can not respond.Data format:The DF51 frequency inverters’ data format corresponds to theModbus data format:PLC (host, master)DF51 frequencyinverter (slave)Requestt LResponsetData nameCoil (bit)Holding register(word)Description1-bit binary data, which can be allocated andchanged.16-bit binary data, which can be allocatedand changed.Function names and numbersFigure 161: Error checkingt L : Latency (waiting time plus PNU C078)hIn this manual, the following standard English names anddesignations for Modbus are used.Table 39:Specified function of the DF51:Function code Function Modbus standard name Maximum datasize (availablebytes permessage)dechexMaximum numberof data elementsper message1 01 Read variable bit (coils) Read multiple coil status 4 32 coils (in bits)3 03 Read word variables (register) Read multiple holding registers 4 4 registers (in bytes)5 05 Write a bit variable (coil) Force single coil 1 1 coil (in bits)6 06 Write a word variable (register) Force single register 1 1 register (in bytes)8 08 Connection test Loop back diagnostic test (00: returnquery data)– –148