Subroutines vs. Add-on Instructions in RSLogix 5000?

Is there any "rule-of-thumb" as when one should use Subroutines vs. Add-on Instructions in RSLogix 5000?

TIA

Use an AOI:
When you do not want to be able to access global variables, without passing them, in the code.
When you find it exciting to guess just how much free memory you need for the temporary memory used by the AOI when calling it.
When you do not want to be able to do online edits of the code.
When you want to use trial and error to find out at which amount of code an AOI saves memory instead of using duplicate code between routines.

But also when:
You need to lock part of the code from future editing.

spaderkung said:

When you want to use trial and error to find out at which amount of code an AOI saves memory instead of using duplicate code between routines.

Click to expand...

By the way, I saw a program designed in india that calls the same subroutine more than 30 times from the main routine, but they change input and output parameters every time they call the subroutine, I wonder in this way, which one is faster or mofe effective AOI or subroutine method.?

Why wonder?

widelto said:

I wonder in this way, which one is faster or mofe effective AOI or subroutine method.?

Click to expand...

Make a loop of 100 iterations an call a AOI and a subroutine that do the same thing. Use the real time clock to time the two and compare.

My hunch is that the subroutine and AOI would compile down to nearly identical code and take about the same a mount of time. If I am wrong it would be good to know which is faster.

An AOI is actually faster then a parameterized subroutine. Usually significantly so.

Each instance of an AOI has its own tag and thus its own memory space. A subroutine does not - it uses the same memory space each time it is called.