Overview and mapping of OPC UA and CODESYS data types

In order to map exported IEC variables from CODESYS in the OPC UA Server, the compatibility of the different, available data types must be ensured. The following two tables list standard OPC UA data types and standard CODESYS data types. A third table shows the mapping between OPC UA and CODESYS data types.

Standard OPC UA data types

Standard OPC UA data types
Data type	Description	Comment
Logic types
Boolean	Truth value	TRUE, FALSE
Integral types
SByte	Signed 8 bit integer	[ -128, 127 ]
Byte	Unsigned 8 bit integer	[ 0, 255 ]
Int16	Signed 16 bit integer	[ -2^15, 2^15 - 1 ]
UInt16	Unsigned 16 bit integer	[ 0, 2^16 - 1 ]
Int32	Signed 32 bit integer	[ -2^31, 2^31 - 1 ]
UInt32	Unsigned 32 bit integer	[ 0, 2^32 - 1 ]
Int64	Signed 64 bit integer	[ -2^63, 2^63 - 1 ]
UInt64	Unsigned 64 bit integer	[ 0, 2^64 - 1 ]
Floating point types
Float	IEEE 754-1985 single precision floating point value
Double	IEEE 754-1985 double precision data type
String data types
String	Unicode string
ByteString	A sequence of byte values
Time and date types
DateTime	A date in the Gregorian calendar with time
UtcTime	Time indication in coordinated universal time (UTC)	All time information between OPC UA servers and clients is in UTC. Clients should offer conversion to local time.
Duration	Specification of a time duration as a floating point value	Double value, that specifies a time interval in milliseconds. Sub-millisecond values can be represented by fractions.
TimeString	Represents a point in time as a string conforming to ISO 8601-2000	Uses 24 hour clock Simple format: [hh][mm][ss] Extended format: [hh]:[mm]:[ss]
DurationString	Represents a time duration as a string conforming to ISO 8601-2000	Format: P[n]Y[n]M[n]DT[n]H[n]M[n]S „P“ (period) introduces the specification. Example: „P3Y6M4DT12H30M5S“ = 3 years, 6 month, 4 days, 12 hours, 30 minutes, 5 seconds
User defined types
Enumeration	Enumeration list
Structure	Structure, composition of fields

Standard CODESYS data types

Standard CODESYS data types
Data type	Description	Comment
Logic types
BOOL	Truth value	TRUE, FALSE
BIT	1 bit logic value	1, 0
BYTE	8 bit logic value	[ 16#00, 16#FF ]
WORD	16 bit logic value	[ 16#0000, 16#FFFF ]
DWORD	32 bit logic value	[ 16#00000000, 16#FFFFFFFF ]
LWORD	64 bit logic value	[ 16#0000000000000000, 16#FFFFFFFFFFFFFFFF ]
Integral types
SINT	Signed 8 bit integer	[ -128, 127 ]
USINT	Unsigned 8 bit integer	[ 0, 255 ]
INT	Signed 16 bit integer	[ -2^15, 2^15 - 1 ]
UINT	Unsigned 16 bit integer	[ 0, 2^16 - 1 ]
DINT	Signed 32 bit integer	[ -2^31, 2^31 - 1 ]
UDINT	Unsigned 32 bit integer	[ 0, 2^32 - 1 ]
LINT	Signed 64 bit integer	[ -2^63, 2^63 - 1 ]
ULINT	Unsigned 64 bit integer	[ 0, 2^64 - 1 ]
Floating point data types
REAL	floating point value, 32 bit	IEC 60559 resp. IEEE 754-2008
LREAL	floating point value, 64 bit	IEC 60559 resp. IEEE 754-2008
String types
STRING	Single byte character string
WSTRING	Double byte character string
Zeit- und Datumstypen
DATE	Date	Prefix: DATE# or D# Example: DATE#1984-06-25 oder D#1984-06-25
TIME	Duration	Prefix: TIME# or T# Example: TIME#14ms T#14.7m T#5d_14h_12m_18s_3.5ms
LTIME	Long duration
TIME_OF_DAY / TOD	Time of day	Prefix: TIME_OF_DAY# or TOD# Example: TIME_OF_DAY#15:36:30.123 oder TOD#15:36:30.123
DATE_AND_TIME / DT	Date and time	Prefix: DATE_AND_TIME# or DT# Example: DATE_AND_TIME#1996-05-06-15:36:30 or DT#1996-05-06-15: 36:30

Features

A direct derivation of elementary types can be made..
Example: TYPE RU_REAL : REAL ; END_TYPE
Subsets of types (Subranges) can be used.
Example: TYPE ANALOG_DATA : INT (-4095..4095) ; END_TYPE

Program Organization Units conforming to IEC 61131-3

Functions
Function blocks
Programs

Mapping between OPC UA and CODESYS Data types

The following table shows the mapping between the data types used for CODESYS and OPC UA.

Mapping zwischen OPC UA- und CODESYS Datentypen
CODESYS data type	OPC UA data type
BOOL	Boolean
BIT	Boolean
BYTE	Byte
WORD	UInt16
DWORD	UInt32
LWORD	UInt64
SINT	SByte
USINT	Byte
INT	Int16
UINT	UInt16
DINT	Int32
UDINT	UInt32
LINT	Int64
ULINT	UInt64
REAL	Float
LREAL	Double
STRING	String
WSTRING	String
DATE	DateTime
TIME	Int64
LTIME	Int64
TIME_OF_DAY / TOD	DateTime
DATE_AND_TIME / DT	DateTime
ENUM	Enumeration
STRUCT	Structure