Making sure data files are actually unused in RSLOGIX 5

[I_rock_well 0]

I have a PLC5 that basically runs 24/7, so that its difficult to in in program mode and new data files. However, any mess up would get very costly very quickly. I want to add a new functionality that requires me to use a large number of integers. There are a whole bunch that appear unused, i.e. they are all zeros and have no 'x' under usuage in the data table. However, the program makes heavy use of relative references, which do not show up under usuage. (and that's just what I am aware off). Is there any other way of checking whether or not those integers are actually free?

[Ken Roach 194]

I think you've encountered one of the unsolvable problems in the PLC-5 world.

I would approach it by finding every indirect address instruction and carefully examining the bounds of each index.    There just isn't another way to find out if that memory is not going to be used by an instruction that uses indirect addressing.

If the risk is high, you've just got to wait for a shutdown in which you can create reserved data tables.