Symbolic Tag Based Addressing
Symbolic Tag Based Addressing
The Beckhoff TwinCAT Driver uses a tag or symbol-based addressing structure. These tags (which are commonly referred to as Native Tags) differ from conventional PLC data items in that the tag name itself is the address, not a physical or logical address.
Client/Server Tag Address Rules
Beckhoff TwinCAT variable names correspond to Client/Server Tag addresses. Beckhoff TwinCAT variable names (entered via Beckhoff TwinCAT PLC) follow the IEC 61131-3 identifier rules. Client/Server Tag addresses follow these same rules and are listed below:
• Must begin with an alphabetic (A-Z, a-z) character or an underscore (_).
• Can only contain alphanumeric characters and underscores.
• First 32 characters are significant.
• Cannot have consecutive underscores.
• Are not case sensitive.
Client/Server Tag Name Rules
The rules for tag name assignment in the server differs from address assignment because tag names cannot begin with an underscore.