FX3U-ENET-L USER'S MANUAL - Automation Systems and Controls

9WHEN COMMUNICATING DATA USING THE MC PROTOCOLMELSEC-F9 WHEN COMMUNICATING DATA USING THE MC PROTOCOLThis chapter explains the message format, how to designate data items in a messageand restrictions for data communication with an Ethernet module using MC protocolwith A compatible 1E frames.9.1 Message Formats and Control ProceduresThis section explains the message format and control procedure for each commandwhen data communication is performed using A compatible 1E frames.The MC protocol for the Ethernet module is a subset of A compatible 1E frames.Both TCP/IP and UDP can be used as lower layer protocol and support both ASCIIcode and binary code.9.1.1 How to read the command reference sectionThe following explains how to read the message explanation diagrams shown in eachof the command description Sections 9.3 through 9.5.(1) When an external device reads data from the PLC(Command message)Externaldevice sideHeaderSubheaderPC No.MonitoringtimerArea APLC sideHeaderSubheaderComplete codeArea B(Response message)1) Area A indicates transmission from the external device to the PLC.2) Area B indicates transmission from the PLC to the external device.3) The program of the external device is generated so that the data istransmitted sequentially from left to right. (For example: in case ofarea A, data should be sequentially sent from Header to the right.)99 - 19 - 1