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KTM Rider

984-485 unresponsive but running?

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I had a problem yesterday where I was called in and found the 984-485 with the power on, but not in run mode. I cycled the power and the plc then did go into run mode but there was an ourbus error light on the remote rack. Also the modbus plus port and modbus port were unresponsive. I rebooted again and this time the ourbus error light went off and everything except the modbus plus and modbus ports was working. The modbus plus light does its normal blink blink blink routine as if there is nothing connected but there is. Also - I cannot connect at all on the modbus port with my laptop. I eventually downloaded the program to a spare 984-485 and installed that - it ran fine. My question is: is there a default modbus setup that the plc reverts to.....? I still cant communicate with the old 984-484 that is now in our test rack.

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Do you know there is a "toggle switch" aside the module? Normally should be on "MEM" position (it means: Modbus settings are taken from software application) but in your case, if you want to be sure of modbus parameters, you could switch to "DIP" and configure the DIP switches on the bottom of the CPU's case. Default settings are (only first 5 switches are used): switch 1 down switch 2 up switch 3 up switch 4 up switch 5 up 9600, 1, 8, parity even

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On the 984-485 the circuitry that controlls the I/O (ourbus) and the comm ports (MB and MB+) is shared. I think that you have a hardware issue here, and the processor should be replaced and repaired. It is true that the Mem/dip switch determines where the setting are read from. Does the MB+ light flash 6 per sec when you connect another MB+ device to the port? This should occur when just two nodes are connected (point to point) unless they are set to the same address.

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