Before using this driver in the PROMOTIC application it is highly recommended to read the chapter:
The communication description by means of the PmaCommGroup object
The
PmaCommGroup objects can be used for this driver.
The variables in the
PmaCommGroup object (or even better the variables in the
PmaData object with
ExtComm data extension) can be of arbitrary number, type and order. The driver uses optimalised internal communication messages for reading the data from the device.
All variables are read (if the "
Data refresh enabled" configurator is checked). When writing into the variable, only the single variable is sent (if the "
Auto send when writing to item" configurator is checked).
Refresh of values of variables registered in the PmaCommGroup object:
While being initialized, the driver registers all variables to the
OPC server (
OPC system message
CreateMonitoredItems) and informs the server about the requested update rate based on the settings of the "
Communication refresh rate [ms]" configurator.
The the driver sends request to be updated when the values of these variables change (
OPC system message
PublishRequest). The
OPC server than, on change of the variable, (or if there is no change, the rate defined in the "
Communication refresh rate [ms]" configurator is used) sends a message containing information regarding all changed variables (
OPC system message
PublishResponse).
After receipt of this message, the driver immediately sends the
PublishRequest message again. This way the values of variables of the
PmaCommGroup object are being updated with defined period
Communication refresh rate [ms].
Description of the "ItemID" configurator:
ItemId is the text identifier of the item that is used for addressing the item in the device. The "
ItemID" configurator tells the driver how to receive or send the item value.
The text can be written manually, or it can be assembled in the window opened by the button to the right of the configurator.
Macro expression can be used for input (it is evaluated after starting the application).
The
ItemId identifier may look like for example "
ns2,str,xxxx", where:
- ns2: Specifies the ns=namespace of the OPC-UA server where the variable belongs (0, 1, 2 ...).
-
str: Specifies the type of variable identifier.
str = The identifier of the variable is a text string.
nmb = The identifier of the variable is a number.
- xxxx: Variable identifier. This text depends only on the OPC-UA server.
| Time reading type | Specifies whether the value time is also read along with the variable value from the OPC-UA server.
If the time is read then this time is saved into the PmVar.TimeSource property.
No - The time value will not be read.
Source - The source time will be read, i.e. the time that the OPC-UA server read from the connected device (if the server is able to read such time).
Server - The time of the value reading by the OPC-UA server will be read. |
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| Maximum number of variables in one registering message | The maximum number of variables that will be registered to the OPC server in one message (OPC message of the CreateMonitoredItems type).
This configurator is off by default (therefore all variables are registered at once using a single of the message).
This configurator usually does not need to be switched on. It must be switched on, for example, when the OPC server does not allow to register many variables in one message (in practice we encountered the limitation of 990 variables). If it is necessary to set some number, then it is best to set this number as high as possible. |
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