1769 all connections may be in use

Hi all,
We have a 1769-L32E PLC which worked very well for 2 years. But recently, I found it can not be connected by RSLogix 5000 software.
When I try to connect the PLC through a Ethernet switch, the software raised a warning: "all connection may be in use". And I cannot use the serial port also, because it has been configured as user mode.
I have tried to connect the PLC directly, without the switch. It works. But the PLC cannot work, because there are a 1734-AENT module, a HMI and several other PLCs connected to this switch.
How can I connect the PLC without disturbing the normal work of PLC? And how can I figure how many connections used in the PLC, how many connections spared to be use?
Thanks very much.

"Logix5000 Task Monitor" is a program that you can get from the Allen-Bradley website. You can use it to monitor the processor for scan times and connections.

Since you can't get connected with everything running, the task monitor probably won't be able to either. So you may need to disconnect things from your switch to free up the connections. I would disconnect one thing at a time (HMI, other PLC, etc.). This will allow you to determine how many connections each device is using.

how many connections do you have to this 1769-l32e? I ran in to a similar problem on a controllogix plc. It wouldn't let me on the web address or anything like that. If I connected direct I could get online but not through a switch. I talked to tech support for 2 days. They said that I hadn't exceeded the limit of connection. They said to upgrade the Ethernet module or replace it. I am still waiting for it to come in to see if it solves the problem.

After unplug the Ethernet cable of my HMI, I can connect to the PLC through the switch. Using Logix5000 Task Monitor, I counted the connections. It was 25.
And when I plug the cable, the HMI cannot communicate with the PLC correctly. Restart the whole machine, everything is OK, except that my PC cannot get online again.
Maybe I have to add a ENB module not use the CPU's ethernet port.

yang1216 said:

Maybe I have to add a ENB module not use the CPU's ethernet port.

Click to expand...

That would increase your available # of connections and fix the issue

Any chance you have a I/P configuration issue? same address or wrong subnet ?

jtashaffer said:

...I ran in to a similar problem on a controllogix plc...They said to upgrade the Ethernet module or replace it. I am still waiting for it to come in to see if it solves the problem.

Click to expand...

yang1216 said:

...Maybe I have to add a ENB module not use the CPU's ethernet port.

Click to expand...

GTUnit said:

That would increase your available # of connections and fix the issue

Click to expand...

Careful,

jtashaffer is referring to an issue with a 1756 ControlLogix platform and 1756 Ethernet Bridge Module, and not a 1769 CompactLogix platform.

This is a 1769-L32E CompactLogix we are dealing with. There is no "ENB" Ethernet bridge module available for the 1769 chassis. There is a 1768-ENBT Ethernet module, or a 1768-EWEB Ethernet module, but they can only be used in a 1768 chassis, which is only present on the left side of a 1768-L4x CompactLogix controller.

So you only have the "CPU's ethernet port" on the 1769-L32E to use in this application.

The 1769-L32E has a limit of 32 CIP connections. Without the HMI connected, you counted 25 connections. The HMI can add up to 5 CIP connections (4 read, 1 write), so this brings it up to a possible 30 connections just while running normal. When you add your PC to the network and attempt to browse/Go Online, you are adding another connection.

This would appear as though you are 1 connection shy of the limit, but the 25 you are seeing, plus the potential 5 from the HMI when connected, may not be a fixed total when you are not online counting. The total can be dynamic, depending on what is configured to communicate with this L32E. If some of the other controllers are passing varying amounts of data to and from this controller, then that connection limit could quite easily be reached, or exceeded.

This 1769-L32E CompactLogix controller is as good as maxed out for the current application setup.

What can you do about it?

Well, you could upgrade the controller to a newer 5370 CompactLogix controller. These support up to 256 connections. A 1769-L33ER, for instance, would allow up to 32 nodes to be added to the I/O Configuration. A node is any device that can be added to the project I/O tree. A node will have its own connection limit, but the limit for all 32 nodes would be 256 connections to the controller. They can pass 6000 packets/sec for I/O and up to 400 messages/sec for HMI/Messaging.

A newer CompactLogix would physically replace an older equivalent fairly easily. Converting an older CompactLogix project to a newer version is also relatively simple. Messaging paths would need reconfiguring, but not much else.

Apart from spending money, one other thing you can try is to force the PanelView application to limit the number of connections it uses at any given time. This can free up a couple of badly needed spare connections.

Since FactoryTalk View Studio ME v5.10, the runtime application will automatically limit the number of connections, to certain limited devices connected to the terminal, to just 1. While the 1769-L2x controllers were added (32 connections max.), the 1769-L3x controllers were not. So you have to implement the following "fix" either through the provided file, or manually, by editing the Windows Registry...

39366 - CIP connections with RSLinx Enterprise (Reducing PanelView Plus connections)
Access Level: TechConnect

Regards,
George