Operator: __TRY, __CATCH, __FINALLY, _

These operators are extended from the IEC 61131-3 standard and they are used for specific exception handling in IEC code.

Syntax

__TRY
    <statements_try>
__CATCH(exec)
    <statements_catch>
__FINALLY
    <statements_finally>
__ENDTRY
    <statements_next>

When a statement in the ‎__Try‎ operator throws an exception, the application does not stop. Instead, it executes the statements below ‎__Catch‎ and therefore starts the exception handling. Then it executes the instructions below ‎__FINALLY‎ . The exception handling ends with ‎__ENDTRY‎. Then the application executes the next statements.

An IEC variable for an exception has the data type ‎__System.ExceptionCode‎.

Example

If the statement in ‎__TRY‎ throws an exception, then program execution is not stopped. Instead, the statement in ‎ __CATCH‎ is executed. Therefore, in this example the ‎exc‎ function is executed and then the statement below ‎__FINALLY‎. Then it executes the instructions below ‎__FINALLY‎.

FUNCTION Tester : UDINT
VAR_INPUT
        count : UDINT;
END_VAR
VAR_OUTPUT
        strExceptionText : STRING;
END_VAR
VAR
        exc : __SYSTEM.ExceptionCode;
END_VAR

__TRY
Tester := tryFun(count := count, testcase := g_testcase);  //Diese Anweisung wird getestet. Wenn sie eine Exception produziert, werden zuerst die Anweisung unter __CATCH und danach die Anweisung unter __FINALLY ausgeführt.
__CATCH(exc)
HandleException(exc, strExceptionText => strExceptionText);
__FINALLY
GVL.g_count := GVL.g_count + 2;
__ENDTRY

For more information, see: ⮫ “Command: Stop Execution on Handled Exceptions ”

Data Type '__System.ExceptionCode'