PLC losing its program when online editing


Thread Starter


The DH+Network has several Rockwell PLC's for various machinery and Process Plant (Soft Drink Manufacture)

The Problem...
When online to this particalar PLC(via DH+network). If you attempt to carry out an Online Edit, the PLC Completely looses its program. After this happens the software has to be re-downloaed.

CPU details:- SLC500
1747-L543C 5/04 CPU 64K Men OS401 SERIES CFF

Does anyone know why this could be? Please

Bob Peterson

I seem to recall running across this problem at one time or another.

I think it was some kind of bug in RSLinx. Do you have the latest versions of RSLogix and RSLinx?
RS Linx Classic. This is the only PLC of many that has this issue. Also we have 2 laptops with the same software on each.... Both give the problem too.

Not sure if Rockwell have updated our Laptops recently with Linx or RSLogix.

I have similar problem with one the 5/05 SLC processor where PLC faults if try to do editing through Ethernet. But if I connect using DF1 serial port it works fine. I don't think it has any thing to do with RSLinx as I can edit program for other SLC/PLC/CTLX over Ethernet/DH+/DH485 without any problem. I am using RS Linx Classic Professional 2.54.00.

Still I am trying to solve the problem whenever I get free time with machine. Anybody who have solved such problem pls. reply.

Checking to make sure you have the latest version of software is always good first step.

I had similar problem with with a PLC-5/40 and it turned out to be that the processor was very low on memory. And the size of the online edits were more than the free memory. So check your free memory. Should have at least 1k free words left.

Another thought, you could try going online through the comm port. This would help narrow down the root cause of the issue.
This is the file size for the Software >232 KB (237,568 bytes)

Controller properties:-

9439 Instruction words used 5875 Data table
48684 Instruction words left

Im not sure how to interpret this data, but maybe you could explain if it adds up OK

The cpu Details are 5/04 64kMem