Licenced variables
In the PROMOTIC system, there are many ways to define a variable. All PROMOTIC variables can be divided into two basic groups: licenced variables and unlicenced variables. The number of variables in PROMOTIC application defines the size of the application and can be detected in the "
Object size and licence" configurator of the
PmaRoot object.
The licenced variables are:
- Data extension
ExtSubVar (Data extension variable
PmVar by subvariable) in variables of the
PmaData object.
- Local variables in scripts (created by statements
var or
Dim).
How to use licenced variables effectively
Data extensions:
Data extensions of variables in the
PmaData object allow to:
- define a variable to be trended (
ExtTrend) - therefore additional variable does not have to be defined in the
PmaTrendGroup object
- define a variable to connect to communication driver (
ExtComm) - therefore additional variable does not have to be defined in the
PmaCommGroup object
- define a variable to communicate via
OPC (
ExtOpcDa) - therefore additional variable does not have to be defined in the
PmaOpcDaClientGroup object
Columns "Read only" in the PmaDataTable object:
Each table cell is counted into the application size for the purpose of licencing. But if a column of table in the
PmaDataTable object is marked as
"Read only", then the cells in this column are not counted into application size. This allows application designers to use this object for storing non-changing configuration values while the number of licenced variables is kept low. From the functional point of view this means that columns marked "Read only" can be written only once. Limitations of individual methods of the
PmaDataTable object caused by "Read only" columns are explained in remark of this method.
Variables in the PmaCommMsg object of the PmChar communication
The
PmChar communication driver allows to assemble communication data in the
PmaCommMsg object. Both data to be sent (on the "
Data-sent" tab) and data to be received (on the "
Data-received" tab).
The variables on both these tabs are licenced.
If you need to assemble a complex message containing many variables then all these variables do not have to be defined on those tabs. There can be just one variable of the
String type on each tab.
- The variable on the "
Data-sent" tab can be set in the script before sending the message. Values from other variables located in other objects can be used.
- The variable on the "
Data-received" tab can be read in the
onEndOfTransfer event. On reading the value, the received
String can be processed in order to get multiple values that are then written into multiple other variables located in other objects.
This way you can use just a single variable in order to send/receive multiple data values.
If the communication is not character based but binary then it can be set to receive such data into the
PmaCommMsg object in the form of
HexaString - see
Binary data transfer.