PmaCommGroup - Deatiled object description
See: the
PmaCommGroup object.
The object is created 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 the "
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 reading both registers and counters in one message.
- 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:
PmOpcUaClient,
PmModbusMr,
PmS7,
PmSBUS,
PmMBus,
PmKNX,
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).
:
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" tab. This identifier can be used e.g. in the
Pm method, or in the "
PP - Data binding to Pma object property" data binding. For example the
Pm("opcdata/#vars/aaa") method returns the
aaa variable 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" tab, it is not needed to define any variables.