An interface parameter is not given a value when the FB is called.
The parameter concerned in the I-DB has the initial value set by the programmer in the FB (0, for example).
The value of an interface parameter is subsequently deleted.
In this case, the last value set at the parameter is stored in the I-DB. If this is not wanted, but would rather use the initial value (0, for example), then you must reload the I-DB into the CPU for initialization or set the parameter with the relevant value (0, for example).
This concerns the parameterization and use of the ARSNO_C, ARSNO_S and ARSNO_V parameters at the PRE_SUM or PR3_SUM block. If this parameter has an archiving ID, the associated calculated value of PRE_SUM or PR3_SUM is archived under that ID.
If the parameter is not switched, the initial value of the parameter is 0 (zero). This corresponds to disabling the archiving of the this parameter.
Accordingly, there is no disabling if the value originally switched is subsequently "simply" deleted. The associated I-DB must be initialized in addition (as described before).
To avoid this step, it is recommended to explicitly set the value 0 (zero) for disabling.
When you install SIMATIC powerrate, a sample powerrate project is installed in STEP 7. This includes a sample configuration and parameterization of a powerrate system.
The parameterization of sample measuring points on PRE_SUM/PR3_SUM at the ARSNO_C, ARSNO_S and ARSNO_V parameters was changed with SIMATIC powerrate V4.0 SP2 upd1 in compliance with the above-mentioned recommendation (see next screenshot).
Disabling of the archiving is now done in the sample project by explicitly setting the value 0 (zero), for example. Beforehand, the parameters in the sample project were implicitly disabled in the case of non-switching by the initial value (= zero) stored in the instance data block (I-DB).
This change simplifies the visibility and legibility of the parameterization. This does not affect the block behavior.