RSLogix 500 Word 17 MSW integral sum

[sapoleon]

Hi again,
I´m still working on the upgrade from 500 to 5000 of this program.
I found something that I cannot explain, in RSLogix 500. It seems when they wrote the program, when setting cascade PIDs, they wrote directly to Word 17, the MSW of the integral sum.
Can someone explain me that form of working? or why did they do that?

Thanks