kolyur
Lifetime Supporting Member + Moderator
I have a Micrologix 1500 with LRP processor. My program has several floating point data files which are used to store machine settings, with about 140 elements in each. These files are only modified by the programmer (me) through RSLogix. There are no write instructions to the files in the ladder logic, I'm certain of that. Data is typically read from the files at various places in the program with indirect addressing, i.e. MOV F[N7:11]:30 F8:0.
The problem is that in one of the floating point files, data in two of the elements keeps getting inadvertently changed. It is always the same data file and the same two elements. These two values are normally whole numbers, like 6.0, but when I connect with RSLogix I sometimes find that they have changed to some crazy number like 9.764696e-40. (Which, by the way, is out of the range of valid floating point values. If I double-click on the number in the data table and hit enter, it won't accept it until I change it.)
I suspect the problem is related to RSLogix communications because I only notice the changes when I go online or do an upload. The machine function would totally go nuts if these values changed while it was running and that hasn't happened (yet). Is it possible for a memory location to get corrupted?
One more thing: There is a Panelview 300 Micro talking to Channel 0 of the PLC through a 1747-DPS1 port splitter. I added the splitter so that I could connect with RSLogix without disconnecting the HMI. (Channel 1 is dedicated to ASCII serial.) The Panelview does not read or write anything to the data files in question.
The problem is that in one of the floating point files, data in two of the elements keeps getting inadvertently changed. It is always the same data file and the same two elements. These two values are normally whole numbers, like 6.0, but when I connect with RSLogix I sometimes find that they have changed to some crazy number like 9.764696e-40. (Which, by the way, is out of the range of valid floating point values. If I double-click on the number in the data table and hit enter, it won't accept it until I change it.)
I suspect the problem is related to RSLogix communications because I only notice the changes when I go online or do an upload. The machine function would totally go nuts if these values changed while it was running and that hasn't happened (yet). Is it possible for a memory location to get corrupted?
One more thing: There is a Panelview 300 Micro talking to Channel 0 of the PLC through a 1747-DPS1 port splitter. I added the splitter so that I could connect with RSLogix without disconnecting the HMI. (Channel 1 is dedicated to ASCII serial.) The Panelview does not read or write anything to the data files in question.