Rockwell Automation Logix5000 Controllers Add-on Instructions Programming Manual - Manual (Page 57)

Defining Add-On Instructions Chapter 2
EnableIn parameter and ladder diagrams
In the ladder diagram environment, the EnableIn parameter reflects the rung state
on entry to the instruction. If the rung state preceding the instruction is True (1),
the EnableIn parameter will be True and the primary logic routine of the
instruction will be executed. Likewise, if the rung state preceding the instruction is
False (0), the EnableIn parameter will be False and the primary logic routine will
not be executed.
Tip: An instruction with only Input parameters, except EnableOut, is treated as an input instruction
(left-justified) in a Ladder Diagram. The EnableOut parameter is used for the rung-out condition.
EnableIn parameter and function blocks
In the function block environment, the EnableIn parameter can be manipulated
by the user through its pin connection. If no connection is made, the EnableIn
parameter is set True (1) when the instruction begins to execute and the primary
logic routine of the instruction will be executed. If a wired connection to this
parameter is False (0), the primary logic routine of the instruction will not execute.
Another reference writing to the EnableIn parameter, such as a Ladder Diagram
rung or a Structured Text assignment, will have no influence on the state of this
parameter. Only a wired connection to this parameter’s input pin can force it to be
False (0).
EnableIn parameter and structured text
In the structured text environment, the EnableIn parameter is always set True (1)
by default. The user cannot influence the state of the EnableIn parameter in a
Structured Text call to the instruction. Because EnableIn is always True (1) in
structured text, the EnableInFalse routine will never execute for an instruction call
in structured text.
You can change the class of a safety Add-On Instruction so that it can be used in a
standard task or standard controller. You can change the class in a safety project if
the instruction does not have an instruction signature, you are offline, the
application does not have a safety task signature, and is not safety-locked.
You can also change the class from standard to safety so that the Add-On
Instruction can be used in the safety task.
Changing the class of an Add-On Instruction results in the same class change
being applied to the routines, parameters, and local tags of the Add-On
Instruction. The change does not affect nested Add-On Instructions or existing
instances of the Add-On Instruction.
Changing the class of an
Add-On Instruction
Rock well Automati on Publication 1756- PM010F-EN-P - Oct ober 2014 57