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

PRG ENTER04/07 AWB8230-1541GB6 Serial interface (Modbus)This section describes the mounting and function of the serialinterface.General information about ModbusModbus is a centrally polled bus system in which the master (PLC)controls the entire data flow on the bus. Internode <strong>com</strong>municationbetween the individual stations (slaves) is not possible.Every data transfer is initiated by a request from the master. Onlyone signal at a time can be transferred along the bus line. Slavescannot initiate a transmission; they can only respond to a request.Two types of dialog are possible between master and slave:• The master sends a message to a slave and waits for a response.• The master sends a message to all slaves and does not wait fora response (broadcast).h Attention!The master cyclically polls slaves’ fault messages. It istherefore advisable to send device-specific and safetyrelevantfault messages directly through the control signalterminals (for example fault indication relays DF51).Example:A short-circuit in the motor conductor at the output of theDF51 switches on the mechanical brake directly.figure 157 shows a typical arrangement with a host <strong>com</strong>puter(master) and any number of DF51 frequency inverters (up to 31stations). Each frequency inverter has a unique address in thenetwork. The addresses are defined through PNU C072 andindependent of their physical position within the network.POWERHzALARMAI ORUNPRGHzAPOWERALARMPRG ENTERI ORUNPRGHzAPOWERALARMPRG ENTERI OPRGRUNHost <strong>com</strong>puterDF51 DF51 DF511 2 32Figure 157:Modbus network with DF51143