Types Of Symbols - Omron CJ2 CPU UNIT SOFTWARE User Manual

5 Understanding Programming
5-5-2

Types of Symbols

The following types of symbols can be used.
Program Symbols

Types of Symbols

• Global Symbols
Global symbols can be accessed from any task in the CPU Unit.
• Local Symbols
Local symbols can be accessed from only one task.
• Network Symbols (CJ2H-CPU6@-EIP or CJ2M-CPU3@ only)
Tags can be used from exterior devices to access the I/O memory of the local CPU Unit through
the network symbols defined in the CPU Unit. Network symbols can also be used in the local CPU
Unit.
Address Allocation
Addresses are allocated to symbols used in programming based on the following factors.
• User Specifications
• Automatic Allocation using the CX-Programmer
The area of memory used for automatic allocations is set by selecting Memory Allocation
Automatic Address Allocation from the PLC Menu in the CX-Programmer.
Type of
Name
symbol
Program Global sym-
symbols bols
Local sym-
bols
Network
symbols
Note "Global" and "local" indicate only the scope of application of the symbol. It has nothing to do with the scope of application
for the memory address. Therefore, a warning but not an error will occur in the following cases, and it will be possible to
transfer the user program.
• The same addresses is used for two different local symbols
• The same addresses is used for a global symbol and a local symbol
5-48
CX-Programmer project tree
PLC tree
Program tree
Global variable table in PLC
tree
Scope
Access
Access
using net-
from other
work sym-
tasks
bols
Not sup- Supported
ported
Not sup-
ported
Supported Supported
CJ2 CPU Unit Software User's Manual
Address
and I/O
comment
Access
(without a
from the
symbol
local task
name)
Supported Supported
Supported Not sup-
ported
Supported Not sup-
ported
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