GE Fanuc 90-30 Series PLC: Varying Register

Hello everybody!
I am experiencing something that seems very weird to me: in one of our automatic napkin machines there is a register in which I set the time a conveyor motor will run, the thing is that no matter what value I set it will change by itself, it increases on its own, and the conveyor throw the napkins all over the place, I tried renaming it from %R004 to %R005, but it does the same, I tried to enter the program from another machine and it does it anyway.
I do not understand what is forcing this register to increase.
Any ideas and thoughts on how to solve this issue are greatly appreciated.
Regards.
Rolando.

With the GE-9030 you have to assign three (3) registers for timers and counters. This is similar to PLC-2s. Accumulated value, preset, status. If you overlap registers or use one of your registers in a different part of the logic, then this could explain why the register changes.

If you can search or do a cross reference for the specific address, then you may find the overlapping address.

The register is being written to somewhere else in the program. Based on your description, I expect that whoever wrote the program overlooked the fact that timers in a 90-30 PLC use three consecutive register addresses. If the first address on a timer is %R0004, that timer also uses %R0005 and %R0006.

Try doing an "implict" search for the register instead of an "explicit" search.

There is a simple way to avoid overlapping addresses in a 90-30. When entering the addresses, just enter "%R" instead of, for example, "%R0008". The software keeps track of the highest address actually in use for each memory type and it will pick the next available address. The technique will not fill in any gaps in the list of addresses used.