Chapter 6. Serial I/O, SNP & RTU ProtocolsGFK-2222AD April 2018 249Message (23): Read Write 4x MemoryPerforms a combination of one read and one write operation in a single Modbus transaction. The functioncan write new contents to a group of 4x registers, and then return the contents of another group of 4xregisters. Broadcast is not supported.Query:The query specifies the starting address and quantity of registers of the group to be read. It also specifiesthe starting address, quantity of registers, and data for the group to be written. The Byte Count fieldspecifies the quantity of bytes to follow in the Write Data field.Here is an example of a query to read six registers starting at register 5, and to write three registersstarting at register 16, in slave device 17:Field Name Example(Hex)Slave address 11Function 17Read Reference Address Hi 00Read Reference Address Lo 04Quantity to Read Hi 00Quantity to Read Lo 06Write Reference Address Hi 00Write Reference Address Lo 0FQuantity to Write Hi 00Quantity to Write Lo 03Byte Count 06Write Data 1 Hi 00Write Data 1 Lo FFWrite Data 2 Hi 00Write Data 2 Lo FFWrite Data 3 Hi 00Write Data 3 Lo FFError Check (LRC or CRC) --
