The following Help section for Data Type > Structure implies that it is possible to compare structures:

"If the target system supports the data type, as from compiler version >= 3.5.7.0 you can compare operands of type STRUCT (structure). Example: IF (stStruct1 := stStruct2) THEN...." .

(I assume this is a typo and should read IF (struct1 = struct2) THEN ...)

Using Control Win V3 Version 3.5.7.10, I have:

TYPE TestDUT :
STRUCT
MyInt: INT;
END_STRUCT
END_TYPE

VAR
struct1: TestDUT;
struct2: TestDUT;
testBool: BOOL;
END_VAR

IF (struct1 = struct2) THEN
testBool := TRUE;
END_IF

This generates the error:
Cannot compare type 'TestDUT' with type 'TestDUT'

Have I made an error or is this feature not supported on the target system?

Hi
not sure that you could still compare structure directly. But you could do it with pointers, using the Sysmemcmp function in library Sysmem.

pstruct1: POINTER TO BYTE;
pstruct2: POINTER TO BYTE;

   pstruct1 := ADR(struct1);
   pstruct2 := ADR(struct2);

IF sysmemcmp(pstruct1,pstruct2, SIZEOF(struct1)) <> 0 THEN
testBool := TRUE;
ELSE
testBool := FALSE;
END_IF

something as above

Great, that's exactly what I need, thanks.