How to preserve the value of an EM parameter

We have an existing equipment module for which we have created a new internal read parameter, the desire is to have the parameter retain its current (online) value during a download. I know this can be achieved as we have another EM on the system where this has been achieved but currently I am unable to replicate this.

Due to this been a parameter within the EM we do not have the option to preserve critical or user defined values as one of the modules properties. A previous suggestion was that this setting was available for the class but this is not the case.

The parameter type is a Floating point with a category of Operating, however we have tested a number a variations but to no avail.

Any ideas would be appreciated.