I’m getting some errors connecting to an S7-300, and I’m not sure what my next step should be in troubleshooting. Here’s the set of repeating events that are filling up my logs…
Is something else connected to this Plc? Older S7-300 processors have very limited connection resources.
You can check the used connections in the rack status.
Here’s the modules I’m dealing with:
CPU 315-2 DP
CP 343-1
Unfortunately, I can’t connect to the CPU online in order to see the occupied connection resources… I can see the CP 343-1, but the connection to the CPU cannot be established. I’m not on site, so I can’t hook up directly at the moment.
There’s an IM 365 extending the main rack, 2 remote I/O racks using IM 153-1’s, and 2 DP/AS-i Gateways listed under the HW Config. There’s also an HMI connected, and an Anybus Gatway for communicating with several Rockwell PLC’s.
In CPU Properties/Communication, the reserved resources are:
PG Communication: 1
OP Communication: 1
S7 Basic Communication: 12
S7 Communication: 0
Maximum Number of Connection Resources: 16
What exactly counts as a connection resource in the S7 series?
Though I can’t connect to the CPU, in the diagnostic buffer of the CP 343-1, there’s a bunch of error messages like this with different CID’s:
Protocol Error
CID of the connection: 33, disconnect reason 85, connection status: 3
External error, Incoming Event
This controller is a part a two identical-ish systems in this plant. The second system is communicating okay, and the controller is reporting the following connection usage:
PG Communication: 1
OP Communication: 2
S7 Basic Communication: 0
Other Communication: 1
Cycle load due to communication: 20%
It’s possible that the systems are more different than they appear to be, but the second system seems to have plenty of communications headroom.
That might be the cause of your problem. I have seen S7-300s that required a hard reset to re-enable communication.
The resource limit of the CP341 should not be a problem. In theory, every connection to a programming device, a HMI or a gateway uses a resource. The DP bus uses another mechanism.
i have an simalar problem, i am trying to connect ignition with an CPU315-2DP including CP 343-1lean card, but i am failing to get it working when i try to ping the plc i am able to reach it, i checked the logs and it succesfully opens the TCP connection but then failed.
i also checked the communications tab in the diagnostics of the siemens CPU
could someone help me to get the communication working?
That “Connection reset” message looks like the kind of error you get when a deep packet inspection firewall decides the traffic is unsafe. Is there a firewall between your Ignition server and the PLC?