Hi,
I am currently running two S7-1515R, in redundancy connected with devices through an MRP ring. One of the devices that are connected to the MRP ring, is an IM 155-6 Profinet node, and in the two outer slots of it I have two CM PtP, which each communicate with some other devices through Modbus RTU.
This is working well, but I have noticed a strange thing about the Modbus cards. When I run the CPUs in redundancy, and I turn the Primary CPU into stop mode, the Backup becomes the Primary, and everything works well. The Modbus communication does not stop communicating at that point.
However, when I turn the one I stopped back into Run, the Modbus stops working, until the one I booted has synced up with the one which is now Primary. Once that has finished, Modbus starts back up by itself. It takes about 90 seconds or so.
I found an SFC which is called RH_CTRL. With this I am able to determine when the CPUs should start synching back up, so that it does not do the usual sync up when I put the new backup PLC into run. So, even if I put the CPU back into run, it will not do any synch until I given it permission.
However, even if I tell it not to synch up and it does not synch, I still get the issues with the Modbus cards when I put the CPU into run.
I do not know why this could become an issue, since the CPU is not participating in synching or running a program, since it wont do that until synced-up. Only change made was change from stop to run.
Any ideas ?
I am currently running two S7-1515R, in redundancy connected with devices through an MRP ring. One of the devices that are connected to the MRP ring, is an IM 155-6 Profinet node, and in the two outer slots of it I have two CM PtP, which each communicate with some other devices through Modbus RTU.
This is working well, but I have noticed a strange thing about the Modbus cards. When I run the CPUs in redundancy, and I turn the Primary CPU into stop mode, the Backup becomes the Primary, and everything works well. The Modbus communication does not stop communicating at that point.
However, when I turn the one I stopped back into Run, the Modbus stops working, until the one I booted has synced up with the one which is now Primary. Once that has finished, Modbus starts back up by itself. It takes about 90 seconds or so.
I found an SFC which is called RH_CTRL. With this I am able to determine when the CPUs should start synching back up, so that it does not do the usual sync up when I put the new backup PLC into run. So, even if I put the CPU back into run, it will not do any synch until I given it permission.
However, even if I tell it not to synch up and it does not synch, I still get the issues with the Modbus cards when I put the CPU into run.
I do not know why this could become an issue, since the CPU is not participating in synching or running a program, since it wont do that until synced-up. Only change made was change from stop to run.
Any ideas ?
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