How do i avoid writing in to fieldbus volatile memory? i often get error while downloading the my pid block
Volatile memory means that what you write is lost if power is turned off. Volatile memor is usually used for dynamic variables such as function block links, not for configuration storage. What exact error message do you get? Control system like DeltaV uses the DD to tell dynamic variables in order to automatically not write to thos variables.
In reply to Jonas Berge:
Few of my pid blocks are assigned to inbuilt block(ff device function block), as a standard every pid module contains one calc block to take pid mode and out to man and zero whenever there is an emergency!!! while i download those modules i get an error avoid writing to ff volatile memory!!!
In reply to bobgally:
Maybe the message refers to non-volatile memory. Is the PID inside a field device? Some field devices have limits on the number of times non-volatile memory can be written. This depends on the type of non-volatile memory used in the device. For instance EEPROM may only permit 10,000 or 100,000 wirtes while other non-volatile permit infinate number of writes. The Target Mode of the block is a non-volatile parameter, so the warning is there to ensure your logic does not inadvartantly "wear down" your non-volatile memory prematurely. For instance, if the logic writes every second the non-volatile memory could wear down in a few hours or days. Instead of writing to MODE_BLK you could consider some change to the logic to use the TRK_IN_D parameter to force a local overrisde mode (LO) that sets the output to the value on the TRK_VAL input (which could be linked from OUT or elsewehere) or you could have logic that only writes the MODE_BLK::Target parameter whenever the value has actually changed (not every cycle) assuming it does not change so often.
thank you jonas!!! now i got what mistake i was doin!!!