Rockwell Automation Logix5000 Controllers Add-on Instructions Programming Manual - Manual (Page 28)

Chapter 1 Designing Add-On Instructions
Programmatic access to data
Input and Output parameters and local tags are used to define an
instruction-defined data type. Each parameter or local tag has a member in the
data type, although local tag members are hidden from external use. Each call to an
Add-On Instruction uses a tag of this data type to provide the data instance for the
instruction's execution.
The parameters of an Add-On Instruction are directly accessible in the controller's
programming through this instruction-defined tag within the normal tag-scoping
rules.
Local tags are not accessible programmatically through this tag. This has impact on
the usage of the Add-On Instruction. If a structured (including UDTs), array, or
nested Add-On Instruction type is used as a local tag (not InOut parameters),
then they are not programmatically available outside the Add-On Instruction
definition.
Tip: You can access a local tag through an alias parameter.
See
Creating an Alias Parameter for a Local Tag on page 31 .
Unavailable instructions within Add-On Instructions
Most built-in instructions can be used within Add-On Instructions. The
following instructions cannot be used.
Unavailable Instruction Description
BRK Break
EOT End of Transition
EVENT Event Task Trigger
FOR For (For/Next Loop)
IOT Immediate Output
JSR Jump to Subroutine
JXR Jump to External Routine
MAOC Motion Arm Output Cam
PATT Attach to Equipment Phase
PCLF Equipment Phase Clear Failure
PCMD Equipment Phase Command
PDET Detach from Equipment Phase
POVR Equipment Phase Override Command
RET Return
SBR Subroutine
SFP SFC Pause
SFR SFC Reset
28 Rockwell Automation Publication 1756-PM010F-EN-P - October 2014