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Data type mapping
Siemens S7 data type
SPEED7 PLC OPC UA data type
OPC UA built-in data type
BOOL
à
BOOL
à
Boolean
BYTE
BYTE
Byte
WORD
WORD
UInt16
DWORD
DWORD
UInt32
INT
INT
Int16
DINT
DINT
Int32
REAL
REAL
Float
S5TIME
S5TIME
UInt16
TIME
TIME
Int32
DATE
DATE
UInt16
TIME_OF_DAY (TOD)
TIME_OF_DAY
UInt32
CHAR
CHAR
Byte
COUNTER
COUNTER
UInt16 (Only valid values)
TIMER
TIMER
UInt16 (Only valid values)
STRING
STRING
String
DT
DT
Byte[8]
Particularities
n
String
–
The data type
STRING
in Siemens S7 is a byte array in which the maximum
length and the current length are stored in the first 2 bytes. The other bytes store
the string.
–
The
OPC UA
data type
String
should be defined in the same way.
n
Array
–
A read or write job in
OPC UA
is always an
Array
access, i.e. always provided
with index and length.
–
A single variable is a special case of an
Arrays
(index 0 and length 1). On the line,
the data type is simply sent several times in succession. For the variable, the
DataType
attribute points to the base data type. The
ValueRank
and
ArrayDimen-
sions
attributes determine if it is an array and how large the array is.
n
Structure
–
A structure describes a complex data type.
–
You can describe your own structures as a subtype of the abstract data type
Structures
, which inherits from the data type
BaseDataType
.
–
Since a client may not know user-specific structures, the variables of the data
type of this structure are uniformly published in an
ExtensionObject
. The structure
ExtensionObject
can be read by any client and also publishes the
DataTypeId
of
the user-specific structure.
–
All structures that are not described by structures of the basic data types are pub-
lished on the server in a
TypeDictionary
.
–
With the description of the structure by the
TypeDictionary
and the
DataTypeId
,
which is published by the
ExtensionObject
, the structure of the
ExtensionObject
can be decoded by a client.
–
If a client knows in advance the description of a user-specific structure, it can be
decoded without reading the
TypeDictionary
. In this approach, a client needs to
read and decode the entire tree to access individual elements.
VIPA System SLIO
Deployment OPC UA
Basics OPC UA > OPC UA data types and their conversion
HB300 | CPU | 013-CCF0R00 | en | 19-30
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