Configuring Database Aggregates Using DATABASE OBJECT

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The DATABASE_OBJECT structure does not allow calling methods or writing to properties of aggregates using Logic. However there is a way that this can be done using two structured text programs. The example code below writes to the ControlMinimum and ControlMaximum properties of all Modbus analog points within a group.

Program 1

The first program, uses DATABASE_OBJECT to get the list of points to operate on. This program can update any of the properties of these points in the class defined by DATABASE_OBJECT, for example, ZeroScale and FullScale. The SQL and DATABASE_OBJECT should also return the FullName property from the class. It accepts an input variable that determines which group it should search in the SQL query. The program uses two Double variables to set the ZeroScale and FullScale named "Range Max" and "Range Min".

As part of the processing of each point, call a second ST program (in the example this is called Sub and is in the same directory as the first program) and pass in the object FullName as an input variable.

Note that both ST programs should be set to "On Interval" with an interval of 0.

 TYPE   ModbusAlgTagName : DATABASE_OBJECT(CModbusPointAlg)   FullScale : INT;   ZeroScale : INT;   FullName : STRING;   END_DATABASE_OBJECT; END_TYPE PROGRAM ConfigurePoints VAR_INPUT   sGroupFullName : STRING; END_VAR METHOD   CallSub AT %M(.Sub.Execute) : STRING; END_METHOD VAR   ModbusAlgTags AT %S(SELECT Id, Units, FullScale, ZeroScale, TrendMaximum, TrendMinimum, FullName FROM CModbusPointAlg WHERE FullName LIKE ? || '%') : RESULTSET OF ModbusAlgTagName WITH_PARAMS sGroupFullName; END_VAR VAR   iRangeMax AT %I(.Range Max) : INT;   iRangeMin AT %I(.Range Min) : INT; END_VAR WHILE ModbusAlgTags.Valid DO   ModbusAlgTags.Value.FullScale := iRangeMax;   ModbusAlgTags.Value.ZeroScale := iRangeMin;   CallSub(ModbusAlgTags.Value.FullName);   ModbusAlgTags.Next(); END_WHILE; END_PROGRAM

Program 2

The second program creates read/write variables that point at the required properties, generating the variable using the FullName which is passed in in the VAR_INPUT block.

Note that we have checked whether or not the Control aggregate is enabled first by checking the $Enabled property to avoid errors when attempting to write to properties on an aggregate that is not enabled.

 PROGRAM Sub VAR_INPUT   FullName : STRING; END_VAR VAR   CtrlMax AT %M({FullName}.Control.ControlMaximum) : INT;   CtrlMin AT %M({FullName}.Control.ControlMinimum) : INT;   Enabled AT %M({FullName}.Control.$Enabled) : BOOL; END_VAR VAR   iRangeMax AT %I(.Range Max) : INT;   iRangeMin AT %I(.Range Min) : INT; END_VAR IF Enabled THEN   CtrlMax := iRangeMax;   CtrlMin := iRangeMin; END_IF; END_PROGRAM

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