Rockwell Automation 1775-KA PLC-3 Communication Adapter Module User Manual - Manual (Page 61)

Addressing Rules and Examples
Chapter 4
4Ć5
Figure 4.4
Symbol Types
User Symbol
Generate this symbolic
value through the
assignment command
Symbol
System Symbol
Generate this symbol
with the Edit command
(for a procedure name)
or a Create command
(for a symbolic address).
Procedural
Applies only to the
procedure in which it is
generated. Interprocedural
Applies to the procedure
in which it is generated
plus any other procedure
nested together with that
procedure Procedure Name
Applies to a single
procedure or other
procedures nested
together within that
procedure.
Global
Applies to any context.
Symbolic Address
Can be used anywhere
in place of a logical
address.
Local
Applies only to the
context in which the
symbol is generated.
10021–I
System Symbols
A system symbol is used as either a procedure name or a symbolic
address. The characters in a system symbol must conform to the general
rules given above for all symbols. System symbols are delimited by the
character @, which distinguishes them from user symbols.
Procedure Names
A procedure name is a way of referring to a message procedure. You
assign a procedure name at the time you generate, or edit, the message
procedure (Chapter 6).
One procedure can execute a second procedure simply by stating the
name of that second procedure. This allows for nesting of procedures up
to three levels deep.
Symbolic Addresses