Beckhoff CX B110 Series Manual page 42

Parameterization and commissioning
Process data with structures
In order to save a large number of links it is a good idea to use a data structure to save data that you wish to
exchange. Note that data structures with different variables are processed differently on an x86 system and
an ARM processor. An ARM processor always associates WORD (2 byte) variables with an even address
and DWORD (4 byte) variables with an address that is divisible by 4.
Data structure sample
byTest: BYTE;
udTest: UDINT;
ARM address
Byte Offset 0
Byte Offset 4
Sum: 8 byte
You can determine the length of a data structure on both systems using the command SIZEOF. If there is a
difference here, this indicates that something is wrong with the data structure.
This problem can be solved by more skillful arrangement of the variables or by working with filler or dummy
variables.
ARM address
Byte Offset 0
Byte Offset 4
Sum: 8 byte
Filler or dummy variables can be used to adjust the length of the data structure, in order to avoid problems
caused by potential differences.
42
ARM variable
Byte
UDINT
ARM variable
Byte
UDINT
Version: 1.3
Address x86
Byte Offset 0
Byte Offset 1
Sum: 5 byte
Address x86
Byte Offset 0
Byte Offset 1
Byte Offset 2
Byte Offset 3
Byte Offset 4
Sum: 8 byte
ARM variable
BYTE
UDINT
ARM variable
BYTE
BYTE (Dummy1)
BYTE (Dummy2)
BYTE (Dummy3)
UDINT
CXxxxx-B110