indirect adress tracine

ippi

Hi All,

I am trying to fault find in a program consisting of just over 200 blocks and have gotten stuck.
something is writing to a shared (when i modify its contents they stay modifiedfor about 1 second then change again)db and i cannot find out what, i've tried all the usual ways of looking in the referance data but come up with nothing actually writing to the block. this leads me to beleive that somewhere indirect addressing is being used to write to it.

how do i work back to find where the data is being written from without going through each and every block

thanks

Overlapping access to memory areas

If you select this option, all the locations in which overlapping address access is used are displayed as well as the locations of the specified absolute address. Overlapping address access means access to addresses, whose address areas overlap with the selected address.

An additional column appears at the start of the list of addresses. This displays the absolute addresses of the address locations which follow.

Laloesco

Hi Ippi
it's hard to find variables with in indirect addressing because the address itself varies on the PLC what I do is export all the program to text file (source code) and then open the file in any text editor and search for instructions used toindirect addres or open DBs.

By other side, if the PLC is on a network, maybe another station is writing this addres with PUT instructions or global data exchange. this kind of acces is not shown in the user program.