FR-A701 INSTRUCTION MANUAL (Applied) - Automation Systems ...

4PARAMETERSCommunication operation and setting(2) OutlineThe Modbus protocol is the communication protocol developed by Modicon for programmable controller.The Modbus protocol performs serial communication between the master and slave using the dedicated messageframe. The dedicated message frame has the functions that can perform data read and write. Using the functions,you can read and write the parameter values from the inverter, write the input command of the inverter, and checkthe operating status. In this product, the inverter data are classified in the holding register area (register addresses40001 to 49999). By accessing the assigned holding register address, the master can communicate with the inverterwhich is a slave.REMARKSThere are two different serial transmission modes: ASCII (American Standard Code for Information Interchange) mode and RTU(Remote Terminal Unit) mode. This product supports only the RTU mode in which 1-byte (8-bit) data is transmitted as-is.Only the communication protocol is defined by the Modbus protocol, and the physical layer is not stipulated.(3) Message formatQuery communicationProgrammable controller (Master)Query MessageInverter response time(Refer to the following table for thedata check time)Inverter (slave)Broadcast communicationData absence time(3.5 bytes or more)Response MessageProgrammable controller (Master)Query MessageInverter (slave)No Response•Data check timeItemCheck TimeVarious monitors, operation command,< 12msfrequency setting (RAM)Parameter read/write, frequencysetting (EEPROM)< 30msParameter clear/all clear< 5sReset commandNo answer1)QueryThe master sends a message to the slave (= inverter) at the specified address.2)Normal ResponseAfter receiving the query from the master, the slave executes the requested function and returns the correspondingnormal response to the master.3)Error ResponseIf an invalid function code, address or data is received, the slave returns it to the master.When a response description is returned, the error code indicating that the request from the master cannot beexecuted is added.No response is returned for the hardware-detected error, frame error and CRC check error.4)BroadcastBy specifying address 0, the master can send a message to all slaves. All slaves that received the message from themaster execute the requested function. In this communication, the slaves do not return a response to the master.REMARKSThe slave executes the function independently of the inverter station number setting (Pr. 331) during broadcast communication.317