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CANbus ISC communication problems

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Hello, I am having problems with a system that uses CANbus ISC. The system has 12 V570 PLCs and used to work correctly. Earlier this year (while the system was unused for a couple of months) we upgraded the OS in all the PLCs, but did not fully test the system after the upgrade. I'm not sure if that's related to our problem, but it's the only thing I'm aware of that changed. Now I am tasked with getting things working again. Everything works except the Network System Bits. The CANbus hardware and communication seems okay. When I remote into one of the PLCs via Ethernet (using it as a bridge) I can download applications or use remote access on any other PLC via the CANbus. That much works fine.

I have taken all the PLCs off the CANbus except two, and written two very simple applications (attached) that should toggle a system bit on one PLC (#6), and read that system bit on the second PLC (#12). These simple applications do not work either. I'm baffled.

Any ideas?





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I tried your apps with OS 3.1, Build 19, using VisiLogic 8.6.1. At first I couldn't get the comms to work, then I tried a slower Baud rate, which worked immediately. Then I put a terminator resistor on the interconnecting twisted pair I had strung between the V570 units, and the 500K Baud connection worked. Removing the terminator made it stop working again. So maybe you're looking at an OS issue which was resolved somewhere between what you're using and the latest? Or perhaps it's a missing terminator someplace...

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Thanks Phil, I upgraded my Visilogic (was 8.0.1) to 8.6.1 which forced me to upgrade the PLC O/S. I only upgraded the O/S on the "listener" so far, but that was enough for my simple bit banger program to work across the net. I expect once I upgrade the O/S on all the PLCs and load the "real" application software it will work again. Thanks again, BoB

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