E - VAE ProSys sro

2.3.3 Format for Modbus RTUGenerally the message format of the Modbus RTU is:T1 T2 T3 Address Function Date Checksum T1 T2 T3with T1...T3:Break periods between two telegrams. The receiver waits for a new address after a breakperiod of at least three and a half character transfer periods.Address:Remark:Function:Substation number of the communication partner.The address is set via the substation number of the PLC Mode device.The following are used by the PLC Mode device from a great number of function of the Modbusprotocol. The type of function code is influenced by the address entry.CodeFunction01 Read spools and discrete output flags. This function code is used if the address isprefixed with a "0". e.g. for reading and display of the first 16 flags #00001XXXX02 Reading of discrete inputs by a "1" prefixe.g. reading of the first 16 input flags #10001XXXX03 Reading of one of more output registersPrefixed by a "4". e.g. reading of the first register and decimal output#40001UUUUU04 Reading of an input register prefixed by a "3"05 Setting of a marker06 Writing of a single register15 Writing of a number of flags is the same as Code 116 Writing of a number of register is the same as Code 317 Detecting of the AEG PLC / diagnosisAttention: Memory types "1" (discrete input flag) and "3" (input register) can only be read; i.e. they mustnot be used in the "Basic definitions" or "variable editing"Check sum: Fault detection operates with CRC-16 and the polynome x 16 +x 15 +x 2 +1E18Process display and control/ Device Manual/ Issue: 07.01