PmCommData - Deatiled object description

See: Object PmCommData
No other PROMOTIC objects can be created in this object. The PmCommData object can be created only in the PmComm object (if the selected protocol supports the usage of the PmCommData object). There can be multiple PmCommData objects in the PmComm object.

This object adds variables into the calculation of the application size, which influences the basic runtime license type/size (see: Price list of PROMOTIC system ).

The object is generated by the type of the communication protocol set by the PmComm object. That's why it is advisable to create the PmCommData object after the configuration of the PmComm object.
An addressing identifier is assigned to each variable defined in this object (see the configurator "ItemID"), that positively defines, haw to obtain the variable value from the communication. The object then intelligently separates the variables into optimised communication messages (creates something like invisible PmCommMsg type objects) and according to the settings in this object takes care of sending or receiving such communication messages.
PmCommMsg and PmCommData objects comparation:
- The PmCommMsg object:
- is a "low level" object, meaning that the data format in this object is created depending on the communication message type, defined by corresponding protocol. If you want to receive, for example, both registers and counters, then two PmCommMsg objects must be created, because the current protocol does not support receiving both registers and counters in one message.
- can be used for all drivers except for the PmS7 driver.
- The PmCommData object:
- compared to the PmCommMsg object, it is on a higher level, because the data in this object are not depending on used protocol. It is possible, for example, to define data for both counters and registers and the object will intelligently assemble this data into communication messages.
- so far this object can be used for following drivers: PmModbusMr, PmS7, PmSBUS, PmMBus, PmIEC8705, PmMelsecQA, PmMelsecFXS, PmABradleyDF1, PmFatek and PmTeco. For some drivers the PmCommData object cannot be used based on the principles (e.g. for the PmChar driver, because this user defined protocol does not have any general addressing and depends only on the user, what kind of message will be created by the PmCommMsg object).
#vars identifier:

In the PmCommData object, the #vars identifer is used in order to enables access to the data items of the Var type defined on the Data page. This identifier can be used in methods working with application object tree (e.g. for the Pm method), or for the PP binding in the application and in panels. For example the Pm("opcdata/#vars/aaa") method returns the aaa data item from the object named commdata that is of the PmCommData type.

Data extension:

The variables in the PmData object can use ExtComm and register itself directly into the PmCommData object. Then, on the page PmCommData > Data, it is not needed to define any variables.

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