PlC5 Ethernet, a warning, a story, and a question

First the warning. PLC 5 series F revison A Ethernet processors have a problem in which if the ethernet port is flooded with traffic it can cause a memory dump and fault the controller. This can be fixed with a firmware upgrade which tech support will help you fix.

How do I know this? Hence the story.

The company I work for decided to "upgrade" 5 production lines from enhanced controllers to ethernet controllers, this decision was made before I joined the company. The purpose of the upgrade was to allow connectivity to our Lan. All of the lines now have a PLC5 ethernet controller connected to an industrial HMI running wonderware via a 3 com smart switch. The HMI's are running personal Oracle and are updating our Alpha oracle at predetermined times. 3 of the lines are 5/20's one is a 5/40, and the other is a 5/80.

The lan network in this plant is a mess. There is Cat5 strung like chicken wire everywhere. The server room consists of a window NT4.0 file server, an Alpha server, 4 old 10MBPS hubs and a WAN link to our corporate office.

On Tuesday, which I am refering to as black tuesday, we had a problem with our lan which caused a hub to start spewing bad packets across our netowrk. The PLC 5/80 and 5/40 and 1 - 5/20 responed by faulting and dumping their programs. The two other 5/20's stopped communicating with their HMI but continued running.

Now the question;

How do I protect the HMI-PLC connection in the event of a Lan problem. I knew enough when entering this project that a 3Com smart switch between the manufacturing network and business network was not enough protection. Being new at the company and not having enough network knowledge to put up a good fight, I couldn't push very hard at corporate IT for a proper solution. I knew that there were enough hard wired controls to prevent this from being a safety concern, however shutting down 2 of these lines is a big deal. It takes 12 - 16 hours to start up one of these lines and if anything goes wrong you have to start over.

From my limited knowledge of ethernet I think that I want a router to segregate the two networks, however somehow this is against company policy? IT told me that the smart switch would protect the HMI to PLC connection, I guess they were wrong costing us $$$$$$$$$. I know this issue has been discussed before but I have searched and can not find a thread that relates. As I said, I knew this wasn't a good setup but thought if anything went wrong with the lan the PLC would shut off it's Ethernet port, not dump the program.

Any advice, links, etc... on what I should do with our network would be greatly appreciated

thanks

Always don't Interconnect office lan with the Industrial lan this will Help always

Not being entirely sure of how your Oracle is retrieving data from the PLC's, but you need to isolate their system from yours.

What info do they need? Come up with a method of concentrating that data into a separate computer or PLC that acts as a "gateway". This "gateway" should have two network cards - each network having different IP address structures. Then their Oracle can come into your gateway on the "other" network.

Also, they should be polling their data at a reasonable rate. How often do they need how much data?

Sounds like a situation where I'd install a managed router between the line (PLC's & HMI's) and the Enterprise network.

The router should be configured to allow only traffic to flow between the Database server(s) and the PLC/HMI network. This is best accomplished using MAC filtering, but that will have to be updated any time the Enterprise connection changes. IP filtering should also work, but is slightly less immune to packet storms.

One absolute though, there should be NO HUBS in ANY ETHERNET NETWORK ANYMORE. Switches cost a tiny bit more than hubs, and hubs are evil.

One other thing to keep in mind, is you can get some seriously nasty packet storms, even on a fully switched network, if you don't have switches that support STP*, or the individual 'Workgroup Switches' do not concantenate into a STP* switch.

*STP = Spanning Tree Protocol, and allows for Star networks to be connected via multiple routes. Without STP, connecting Port 1 on a switch to Port 2 on the same switch (or any such 'connect to self', as in an Ethernet ring configuration) is absolutely disasterous.

The Alpha is pulling basic production data such a line speed, length produced, downtime, etc....

There is about 100 tags of data polled out of every machine every two hours by the Alpha server.

We upgraded our only 5/40 to a 5/40E (Used Series C, Rev. D) this year. The HMI still uses DH+, and the Ethernet is used for data logging and PLC communication. We have a managed switched network with a router between the company network and the PLC network. If I tried to do much more than data logging, it would dump. I did the upgrade and all is now well, so the upgrade does work.

rdrast is right. I would address your network issues also.

Good luck!