Creating Logic for the Add-On Instruction
Follow these steps to enter logic into your project.
1. In the Controller Organizer, expand the Add-On Instructions folder.
2. Expand the instruction and double-click the logic routine to open.
3. Edit your logic by using the available language editors.
Execution Considerations for Add-On Instructions
An Add-On Instruction is executed just like any other routine belonging to a particular program. Because another task can preempt a program containing an Add-On Instruction that is being executed, an Add-On Instruction may be interrupted prior to completing its execution.
In standard programs, you can use the User Interrupt Disable/Enable (UID/UIE) instructions to block a task switch if you want to be sure the Add-On Instruction executes uninterrupted before switching to another task.
Optimizing Performance
The performance depends on the structuring, configuration, and the amount of code in an Add-On Instruction. You can pass large amounts of data through a structure by using an InOut parameter. The size of data referenced by an InOut parameter does not impact scan time and there is no difference between passing a user-defined type tag or an atomic tag because it is passed by reference.
When a rung condition is false, any calls to an Add-On Instruction are still processed even though the logic routine is not executed. The scan time can be affected when many instances of an Add-On Instruction are executed false. Be sure to provide instructions in your documentation if an Add-On Instruction can be skipped when the rung condition is false.
1. In the Controller Organizer, expand the Add-On Instructions folder.
2. Expand the instruction and double-click the logic routine to open.
3. Edit your logic by using the available language editors.
Execution Considerations for Add-On Instructions
An Add-On Instruction is executed just like any other routine belonging to a particular program. Because another task can preempt a program containing an Add-On Instruction that is being executed, an Add-On Instruction may be interrupted prior to completing its execution.
In standard programs, you can use the User Interrupt Disable/Enable (UID/UIE) instructions to block a task switch if you want to be sure the Add-On Instruction executes uninterrupted before switching to another task.
Optimizing Performance
The performance depends on the structuring, configuration, and the amount of code in an Add-On Instruction. You can pass large amounts of data through a structure by using an InOut parameter. The size of data referenced by an InOut parameter does not impact scan time and there is no difference between passing a user-defined type tag or an atomic tag because it is passed by reference.
When a rung condition is false, any calls to an Add-On Instruction are still processed even though the logic routine is not executed. The scan time can be affected when many instances of an Add-On Instruction are executed false. Be sure to provide instructions in your documentation if an Add-On Instruction can be skipped when the rung condition is false.
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