In my project, I have server-PLC (Siemens S7-300) communication with the following connections:
Now, let say we call the connection between Server and Network Switch/Router as A, and connection between Network Switch/Router and the PLC as B
I am doing some tests on the system, and one of them is to physically disconnect connection B and monitor the result from the Ignition Gateway and Ignition Designer.
Now, usually, the Generic TCP/IP driver shows the number of connected device on certain connection like this in the Gateway -> OPC-UA -> Devices -> Status Column:
Throughout my testing, I notice that when I disconnect and reconnect connection B five possible things may occur:
- The number of device connected shown in the Gateway -> OPC-UA -> Devices -> Status Column, sometimes - and not always, is increased by 1 upon re-connection, though there is no actual new device connected:
- Likewise, when a device is disconnected, it, sometimes and not always, does not reduce the number of connected devices:
When the device is disconnected, the tag in the Ignition Designer still shows DataQuality as good (!) though the actual connectivity is missing.
When connection B is reconnected, if case 1 does not occur (that is, the number of connected device does not increase), then we cannot get updates from the device anymore!
When I use multiple ports to refer to the exact same devices (for the device could configure multiple connection ports) which originally show the same number of connected devices (say, 3), and then if I test the connection and re-connection, the increment/decrement behaviors are not consistent among the ports. That is, one port may have incremented connection:
While the other port remains:
And when that occurs, the port which does not increase the number of device connected can no longer communicate with the device.
I did not seem to encounter those issues when I tested without using direct connection
What could be the reason and how to solve it? Admittedly, the Network Switch/Router are connected to more than one devices. Could that cause those issues? How to solve them?