PLC5/40 DH+ Communication Issues

I have an odd problem with a PLC5. This is a long-time existing unit, not a new installation.

It is on a network of 7 DH+ Devices, 2nd from the end of the line. A panelview is at the end of the line.

The problem is, I can't see the PLC5 in RSLinx, but I can see the Panelview and all other devices. The comm status light on the processor is a steady green. If I unplug the DH+ cable from the front of the PLC, I get a communications error on the corresponding panelview, and the status light will blink. All data on the corresponding panelview seems accurate and is changing.

ideas?

Swag

Check your node addresses, your laptop/pc and the PLC may have the same node address. Try changing the laptop to a known unused node address, and see what happens.

I'm communicating over ethernet to an ethernet/ DH+ Gateway, so my PC has no address.

I have not used a Gateway so I am just thinking out loud.

I assume the gateway has an IP address for the ENET connection AND a node address for DH+. It may be possible it is using the same address as that PLC5 but since it does not actually provide traffic there may not be a conflict until you attempt to access that PLC5.

Just a thought.

Thanks for the responses.

One of my most feared problems are the ones that fix themselves.

I've been fighting this all morning, I went to lunch and when I returned everything was fine.

As with Murphy's Law, this thing won't rear it's ugly head until Saturday afternoon after I've had a few cold ones during the 4th quarter of a tie football game.

Have a good weekend!

If this is an intermittent problem, check that the termination resistors are properly installed on the DH+ cables (one at each end). I have seen this problem on DH+ and RIO caused by missing or improperly installed resistors.

Well, I couldn't have called that one better. The call came at 7:00pm Saturday night, just as I was getting comfy with my bride.

The problem is, it was on a different network. Actually, three other networks. The only thing common with these was the ethernet.

I don't know if we are having some type of electrical issue or what. We ended up needing to replace one processor, the others came back up after a re-boot. All was good after a few hours.

Now, Monday, back at work and as soon as I walk in, I hear the problem is back (my original post)

Starting to dig in again. Atleast it isn't Friday afternoon.