Honeywell HC900

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I am having trouble with a HC900 C50 CPU. It’s connected to a hakki HMI and on certain instruction performed on the screen it faults out the CPU.

I have 3 strobes on the led which in the manual indicates a CPU prefetch abort error. It says to replace the CPU which I have done but the fault occurs on the new one too.

I have replaced the HMI and comms cable between them but nothing has helped stop the fault occurring.

Any ideas on next actions welcome 

Edited by Cryan9954
PLC hep

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1.  Did the HMI ever communicate successfully with the CPU, or is this a commissioning/start-up problem?

2.  What HMI instruction faults the HC900 CPU?

3.  Which version firmware is the HC900 CPU running?

4.  Which hardware comm is for CPU/HMI comm?  Ethernet or RS-485?

5.  Is the HMI the Modbus Master, HC the Modbus slave?

6.  Are the CPU’s genuine Honeywell, or the fake, knock-off made in India models?

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