1766-RM001A-EN-P MicroLogix 1400 Programmable Controllers ...

418 Communications InstructionsData Table AddressThis variable defines the starting address in the local controller. Valid filetypes for the Data Table Address are shown below:Message ReadBit (B)Timer (T)Counter (C)Control (R)Integer (N)Floating Point (F) (1)Long Word (L)String (ST)Message WriteOutput (O)Input (I)Bit (B)Timer (T)Counter (C)Control (R)Integer (N)Floating Point (F) (1)Long Word (L)String (ST)Real-Time Clock (RTC) (2)(1) Message Type must be 500CPU or PLC5. The Local File Type and Target File Type must both be Floating Point.(2) 500CPU write RTC-to-Integer or RTC-to-RTC only.TIPOnly Bit (B) and Integer (N) file types are valid for Modbus Commandmessages. Modbus bit commands require a starting bit address for theData Table Address.Floating Point (F) and Long (L) file types are valid for Modbus Commandmessages for Holding Registers (commands 03, 06 and 16) when Data isconfigured for 32 bit.Size in ElementsThis variable defines the amount of data (in elements) to exchange withthe target device.The maximum amount of data that can be transferred via a MSGinstruction is 103 words (120 words for Modbus commands) and isdetermined by the destination data type. The destination data type isdefined by the type of message: read or write.Publication 1766-RM001A-EN-P - October 2008