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TOM_80

Monitoring a register

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How do you ensure a time value in a memory register coming from an external device is constantly changing in an omron cj2 plc and trigger an alarm when it stops. At my company we scan in a work order with a barcode scanner tied to a different network than the one the plc is communicating to. We use a specific register in memory to determine if these two networks are communicating. We use a date time value in seconds going to that specific register, as long as the time continues to run we know we have a communication link. If that time ever stops in that register we know the communication link is severed. I need to know if there is logic that can be written in the plc to notify an operator when there is no communication link.

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Sure, something like this should work:

5e568aad0a0e3_commmonitor.jpg.f7f4d80eda

If D100 = D101 for 1.0s or more, the link severed bit turns on.  D100 is the value to be monitored and D101 is the last value that D100 changed to.  Of course you can change the set point of the timer to be something longer than &10 (1.0s).  

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Note:  swap the order of the two rungs above.  Have the rung with the = instruction and timer be first and have the rung with the <> and MOV instruction be second.  It will not reset properly if you have them in the order that I have them above.  

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Thank you very much Michael for that, that just might work.

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