How to troubleshoot a Unity ERIO Hot Standby system at start up.



Unity Quantum Hot Standby Ethernet Remote IO configuration will not go to Run Primary

Product line
Unity Pro, Quantum


*****140CRP31200 firmware must be at a minimum of v1.64*****

A good starting point is to eliminate the essential hardware as the source of the problem. Work with the minimum required modules. In each PLC backplane, only use the PS, CPU and CRP. Set up a single ERIO CRA drop that only includes the PS and CRA in the backplane(a drop is required if at least one is mapped*).
Make the following connections:
1: HSBY Link between the two CPUs.
2: CRP(a) ETH3 to CRP(b) ETH3
3. CRP(a) ETH4 to CRA ETH2
4. CRP(b) ETH4 to CRA ETH3

These are the minimum connections and hardware required for a Unity Quantum ERIO Hot Standby system. After setting up and connecting all of the above hardware, only power up a single CPU and the CRA backplane. Load the program into the CPU and it should come up in Primary mode when placed into Run. You can test both sides independently to make sure that they come up Run Primary. If they come up as Run Primary independently, leave the Primary powered up and then power up the other PLC while Holding the ESC key. Release the key after the erasing RAM message appears and at the end, it should come up as RUN Standby.

As previously stated this is a good starting point, if it comes up in Run Primary and Run Standby, you can then start adding your additional hardware and switches.

*If you have no CRA modules configured, simply connect CRP 3 to CRP 3 and CRP 4 to CRP 4. (You actually only need one of these connections)

*If you have CRA modules configured but need to test before you get them, set %S84 to a 1, this will allow
Run Primary / Run Standby with the configured drops missing. You still need to make the CRP to CRP connections.

*** Setting %S84 to 1 will cause the CPU to ignore the Ethernet port connections on the Primary CRP. This means that if you were to pull both cables off of the Primary CRP, the Primary will stay as Primary and the Standby will go offline because he can see that the Primary CPU is healthy VIA the fiber connection but can not see the other CRP from its own copper connection so it assumes it has an issue and drops offline. The actual health of the CRP is still monitored, if the CRP were to fail, there would by default be a switchover. If using %S84 you can add code to monitor the Primary Ethernet Ports 3 & 4  to make sure they are healthy and force a SWAP if they are not.  *** 

 If after the above you still can only achieve Run Primary / Run Offline, try setting %SW60 to 30(allow program and firmware mismatch). If it goes Run Standby, you either have a firmware mismatch between the CPUs or CRPs or a program mismatch.  %SW61.4 will be 1 if the program is mismatched. %SW61.7 will be 1 if either CRP or CPU firmware is mismatched. %SW61.8 will be true of CoPro is mismatched.