rslogix structured text- add on instruction - variable declaration

[italo2008]

I've created an add-on instruction in rslogix 5000 (in structured text) but I can't test it and I need to know if it is correct..

in a rung of the main routine I call my add on instruction giving some controller tags as input parameters to he funtion. In the add on instruction can I modify these tags if I have declared them as InputOutput variables? Or I must define them as Local variables?

If I've decleared them as InputOutput variables, what happens if the function modify one of them? (I hope that the controller tag wich has been given as input parameter to the function will be modified... isn't it?)

 

[TConnolly]

If you have declared them to be InputOutput variables and you modify them in the AOI then the original Controller Scoped tags are also modified. If you want to modify the values internally but not modify the original tags then use local AOI variables.

If you wish you can export the AOI to an L5X file and post it - we'll be happy to take a look at it for you.