The datatype mapping for parameter data is described in Table 70.

Table 70 – Mapping of simple data types

OPC

FDT

Data type

Data type

Description

Float

Float

Double

Double

Byte

Byte

Int32

Int

Int64

Long

UInt32

UInt

UInt64

ULong

DateTime

DateTime

DateTime

Date

Date is represented as date at 0:00 a clock.

Duration

Time

Time is expressed as duration since midnight.

Duration

TimeSpan

Duration is expressed in milliseconds, TimeSpan is expressed in terms of days, hours, minutes. For the conversion of large TimeSpan a loss of precision may occur.

String

String

Array of Byte

BinaryByteArray

Array of Bit

BinaryBitArray

Enumeration

Enumerator

Boolean

Boolean

SByte

SByte

In OPC UA array datatypes are represented by a combination of the properties datatype, value-rank and array-dimensions (see OPC OPC UA 10000-5, section 5.6.2).

In FDT array datatypes are represented with a dedicated ArrayDatatypeInfo datatype. This datatype has a member ArrayDatatypeInfo.ArrayDimensions, which specifies the length of each dimension of the array.

The mapping for array data types is defined as follows.

  • OPC datatype value is mapped according to Table 70.
  • OPC value rank is:
  • -1 for a simple datatype, or
  • Number of fields in FDT ArrayDatatypeInfo.ArrayDimensions (always > 0)
  • OPC array-dimensions property is:
  • NULL for a simple datatype, or
  • has the same value as ArrayDatatypeInfo.ArrayDimensions.

value of 0 means that the array has a variable length,

values > 0 indicate a defined length.