Maximum HMI Connections to SLC 5/05

[Sector7 0]

Hi, I am try to connect (16) ProFace HMIs to (1) AB SLC 5/05 via Ethernet. I started with 5 HMIs and the PLC and all was well. Since the other 11 HMIs have been installed, I have been unable to get all 16 HMIs to communicate to the PLC. If I disconnect the Ethernet cable from all HMIs and go one by one, all HMIs have a good connections and will communicate with the PLC. It is only when I connect all that most will not communicate. It appears to be a problem with the number of connections since the first HMIs that I re-connect the Ethernet cable to will establish a connection with the PLC. It appears the the first 8 (I think 8) connected will establish comm and work as expected. When I see this problem, RS Linx cannot find the PLC. It comes back with a 0x01E00204 status followed by a 0x00000005 status. I can still ping the PLC, but not connect to it. I thought I understood that the SLC 5/05 1747-L552 was able to handle 32 simultaneous TCP connections. Does anyone know what I am doing wrong or if I am just misunderstanding the maximum number of connections? Thank you

[Armadillo852 25]

Here is what AB says. http://rockwellautomation.custhelp.com/app...552/r_id/109439 It looks like either 16 or 24. Series C FRN 5.16 increased the ethernet connections of the L552 and L553 to a maximum of 24.

[PMersault 1]

Bear in mind that a typical data server connection does not use just one TCP connection. I'm not familiar with ProFace, but for example, RSLinx Enterprise uses up to 5 at a time, while RSLinx Classic could be configured to use up to 20. You might check with ProFace to see if they have similar information on this, as well as how to scale back the number of connections used (if possible.)

[kaiser_will 65]

This sounds like packet dropouts or collisions, since you have solid comms with a smaller number of HMIs connected. You might want to consider adding some heartbeat diagnostic logic (pull separate HMI status bits into the PLC, activating timers when status is lost - time out and latch an alarm bit). How are your verifying connectivity? Look at the SLC-5/05 Channel 1 settings. I have used a free Ethernet/IP sniffer program to troubleshoot network setups (Free IP Scanner). Disconnect the system from your company network (if possible) and turn off your programming computer wireless connection (if using a laptop) to limit the extraneuous network traffic, limiting the program to sniffing only the hardware you are interested in. http://www.eusing.com/ipscan/free_ip_scanner.htm Also, look at your network Ethernet/IP configurations. For instance, I would imagine you are using a multi-port Ethernet switch and might need to limit broadcast traffic (IGMP Snoop set to off). PLCs and HMIs can bombard your network with broadcast traffic, and the switch will limit the traffic thus reducing the overhead of the network (high overhead could be dropping packets, increasing as you increase devices). I authored this Ethernet-Ethernet/IP Primer some years ago to bring engineers up to speed on networking details Primer___Ethernet_and_Ethernet_IP.doc

[Sector7 0]

Thank you all for the good information. I appreciate the responses. kaiser_will: Thanks for the suggestions. I am going to work on this project this weekend. I will try to sniff the LAN as you suggested as well as modify and LAN configurations. I will post the results soon. As far as verifying the connections, when all HMIs are connected to the network, only the first 8 will display information from the PLC. All others will display an error message about "invalid initial command response" and another one about "socket error". Sorry I do not have the exact messages with me. Edited 9 Jul 2010 by Sector7

[Ken Roach 194]

If the 1747-L552 controller is new, then it supports up to 48 TCP Connections; 4 reserved for Incoming, 4 reserved for Outgoing, and 40 that can be allocated either direction. RA Knowledgebase document AID # 17469 describes the TCP connection capacity and history of SLC-5/05 controllers in detail. With regard to a single device's connections, there is some confusion about TCP Connections versus CIP Connections. CIP is the application protocol used by ControlLogix and shared by some aspects of the SLC-5/05 controller. It was mentioned that RSLinx Enterprise by default consumes 5 CIP connections. It does do so, but it only uses one TCP connection to carry them all. The larger issue is the fact that you're connecting sixteen HMI terminals to a single controller. I think your problem is simpler than TCP or CIP connections. Imagine a diner with sixteen stools at the counter. You could seat sixteen customers, no problem. If they were each just having coffee and toast, that's fine. But if each one of them is ordering burgers and fries and milkshakes and needs a refill of Coke and a napkin and dropped their fork and wants the check and.... you get the idea. If there's only one waitress, she's not going to be able to get to all sixteen customers fast enough to satisfy them. She won't miss their orders, or forget their requests, but by the time she gets around to them they've walked out. The SLC-5/05 has only the one CPU; it handles the communications as well as the logic control. That's the waitress. The timeout is just the application setting from the Proface device. So; can you teach your Proface devices to be more patient ? How about limiting how much they order ? Start by sniffing the amount of traffic put onto the SLC port by a single HMI. Then add another. Then another. You'll get the idea.

[Sector7 0]

I tried playing with the HMI timeout and retries, but it did not seem to help. I tried sniffing the network with Wireshark, but only seen broadcast messages as I only had an unmanaged switch. I am going to try sniffing again, first with one HMI, then adding another, etc with a dumb hub or managed switch. It will be next weekend before I have any more information. The weekends are pretty much the only time I have to work on this project. I do appreciate all the advise everyone has given so far.

[kaiser_will 65]

Another resource is to contact your local Hirschmann industrial Ethernet distributor or sales agent. I have been using their products for years, not only for their cost effective reliability but to deal with multi-port Ethernet communication issues such as this. If you cannot tweak the CPU and HMI communication parameters to get reliable communications, your unmanaged switch may be the weak link. Here is a Hirschmann white paper dealing with interoperability within an A-B environment. Hirschmann_Switches_in_a_A_B_Environment.pdf

[Sector7 0]

Ok, here is what I have done and found: I borrowed a managed switch configured to mirror all traffic to one port for sniffing. I connected my laptop running Wireshark, luckily with Ethernet/IP and CIP dissectors built in. With the PLC and one HMI, the traffic was about 0.072 MBit/s. With the PLC and two HMIs, the traffic was about 0.117 MBit/s. This did not seem like a lot, so I jumped to eight HMIs and the PLC, the traffic was about 0.223 MBit/s. When I added the ninth HMI, it was not able to connect (pro-face gives and error message and screen does not display correctly). I checked the data on Wireshark and found that the TCP connection was successful. I saw the complete three step handshake connection. Next, I saw the HMI request a CIP session. The PLCs response to this was to close the TCP socket. From here I could tell that this was not an issue with TCP. I googled maximum number of CIP connections for a SLC 5/05 and found this pdf: http://192.94.123.20/idc/groups/literature...rn009_-en-p.pdf In here it states that AB increased the maximum number of CIP connections from 8 in FRN 5 to 24 in FRN 6. It turns out my processor has FRN 5. I borrowed an L551 FRN 10 and loaded it up (I had to removed some features of my logic because of smaller memory). Sure enough I was able to get 9 HMIs all communicating with the PLC at one time. Next, I removed the borrowed managed switch and went back to the series of switches I currently have to see if it would work. Luckily I was able to have 15 HMIs communicating with the L551. At least for know I think I may be safe on my switch configuration. From the paper kaiser_will gave, I think this is something I need to keep in mind for the future. With all that said, I do not know how to upgrade the firmware. I found a pdf that tells how to upgrade a SLC 5/05 with Control Flash. I have found other posts where Mr Roach shows where to get upgrades for MicroLogix, but I cannot find anywhere how to get firmware upgrades for the SLC. Thank you again for all of the help and input. I think with all of your help I have made progress. I will let you know if the firmware upgrade solves the problem....as soon as I can locate it

[ScottC 8]

The firmware upgrade is not available for download. You have to order it - catalog number 1747-DU501. Scott

[Sector7 0]

Thanks Scott. I have a hard time finding things on AB's site. I looked for about an hour for firmware the other day.

[Sector7 0]

Well, I searched our shop and found an L552 with firmware FRN 6. I installed and loaded it and all is well now. We have to install another system like this and I plan to order the OS upgrade and install on the old processor. Thank you all for your help.