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

3SPECIFICATIONSMELSEC-F3.6 List of Applications and Assignments of the Buffer MemoryData transmission/reception between Ethernet Module and PLC is performed via theEthernet Module buffer memory (hereinafter called BFM).Reading/writing data in the buffer memory from the PLC must be performed by theFROM/TO instructions (instructions that can access BFM).In addition, the initial value of the buffer memory or the internally stored value iswritten when the power is turned on.(1) Configuration of the buffer memoryBuffer memory consists of a user area and a system area, as listed below.(a)(b)User areas1) The areas where the user writes/reads data.2) A user area consists of a parameter area for initial processing and datacommunication, an area for data communication, and an area for storingcommunication status and communication error data.3) Reading/writing data to the user area should be performed according tothe instructions in the corresponding detailed explanation section.Data communication may take longer if continually executed; therefore,execute only when needed.System areasThe areas used by the Ethernet moduleImportantDo not write data in the "system areas" of the buffer memory.If data is written to any of the system areas, the PLC system may not operateproperly.When writing a value to the buffer memory including "System Area," pay closeattention not to change the system bit.3 - 83 - 8