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PmaCommGroup - Deatiled object description

See: Object PmaCommGroup
 
The object is generated by the type of the communication protocol set in the PmaComm object. That's why it is advisable to create the PmaCommGroup object after the configuration of the PmaComm object.
 
An addressing identifier is assigned to each variable defined in this object (see "ItemID" configurator), that positively specifies, how to obtain the variable value from the communication. The object then intelligently separates the variables into optimised communication messages (creates something like invisible PmaCommMsg type objects) and according to setting in this object takes care of sending or receiving such communication messages.
 
PmaCommMsg and PmaCommGroup objects comparation:
- The PmaCommMsg 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 PmaCommMsg 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 PmaCommGroup object:
- Compared to the PmaCommMsg 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.
- Can be used for following drivers: PmModbusMr, PmS7, PmSBUS, PmMBus, PmIEC8705, PmMelsecQA, PmMelsecFXS, PmABradleyDF1, PmFatek and PmTeco.

For some drivers the PmaCommGroup object cannot be used based on the principles (e.g. for the PmChar communication 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 PmaCommMsg object).

 
#vars identifier:

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

 
Data extension:

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


History:
Pm8.00.00: Created
PROMOTIC 9.0.3 SCADA system documentation - MICROSYS, spol. s r.o.

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