Why is last value not retained in PP846 in case of power on-off ?
During the situation of power on-off, PP846 panel is unable to retain the last values. Though the values in the controller are “cold-retained” but when the “write” operation is performed through PP846 the of retention is encountered after power shut down. The values in PP846 are reset when the power comes back and when the writing operation is performed, the values in controller are overwritten.
Software ( Panel 800 ) version : ver5.1.4
Communication Protocol : Profibus
This type of retention problem is not encountered in CP panel series and “HACO” make panel series.
Kindly help in resolving the issue as the situation is quite critical since commissioning is going on.
"The values in PP846 are reset when the power comes back and when the writing operation is performed"
It sounds like you are doing something odd here. The PP846 - or any other panel - should not write to the PLC unless you do something to make it write - like pressing a button to write a single value for example. It is your responsibility to make sure that what you write is "valid" - ie you have previously read the current value from the PLC before wrting data back to the PLC again.
The panel is not suposed to "cold-retain". The panel can operate with a range of PLC's, not just the AC800M.