Nodedefinitions are specified using tables (See Table 1)

Table 1– Type Definition Table

Attribute

Value

Attribute name

Attribute value. If it is an optional Attribute that is not set “--“ will be used.

References

NodeClass

BrowseName

DataType

TypeDefinition

ModellingRule

ReferenceTypename

NodeClassof the TargetNode.

BrowseNameof the target Node. If the Referenceis to be instantiated by the server, then the value of the target Node’s BrowseName is “--“.

Attributesof the referenced Node, only applicable for Variablesand Objects.

Referenced ModellingRuleof the referenced Object.

Notes –

Notes referencing footnotes of the table content.

Attributesare defined by providing the Attributename and a value, or a description of the value.

Referencesare defined by providing the ReferenceTypename, the BrowseNameof the TargetNodeand its NodeClass.

  • If the TargetNodeis a component of the Nodebeing defined in the table the Attributesof the composed Nodeare defined in the same row of the table.
  • The DataTypeis only specified for Variables; “[<number>]” indicates a single-dimensional array, for multi-dimensional arrays the expression is repeated for each dimension (e.g. [2][3] for a two-dimensional array). For all arrays the ArrayDimensionsis set as identified by <number> values. If no <number> is set, the corresponding dimension is set to 0, indicating an unknown size. If no number is provided at all the ArrayDimensionsmay be omitted. If no brackets are provided, it identifies a scalar DataTypeand the ValueRankis set to the corresponding value (see OPC 10000-3). In addition, ArrayDimensionsis set to null or is omitted. If it can be Any or ScalarOrOneDimension, the value is put into “{<value>}”, so either “{Any}” or “{ScalarOrOneDimension}” and the ValueRankis set to the corresponding value (see OPC 10000-3) and the ArrayDimensionsis set to null or is omitted. In Table 2examples are given.

Table 2– Examples of DataTypes

Notation

DataType

ValueRank

ArrayDimensions

Description

Int32

Int32

-1

omitted or NULL

A scalar Int32

Int32[]

Int32

1

omitted or {0}

Single-dimensional array of Int32 with an unknown size

Int32[][]

Int32

2

omitted or {0,0}

Two-dimensional array of Int32 with unknown sizes for both dimensions

Int32[3][]

Int32

2

{3,0}

Two-dimensional array of Int32 with a size of 3 for the first dimension and an unknown size for the second dimension

Int32[5][3]

Int32

2

{5,3}

Two-dimensional array of Int32 with a size of 5 for the first dimension and a size of 3 for the second dimension

Int32{Any}

Int32

-2

omitted or NULL

An Int32 where it is unknown if it is scalar or array with any number of dimensions

Int32{ScalarOrOneDimension}

Int32

-3

omitted or NULL

An Int32 where it is either a single-dimensional array or a scalar

If the NodeIdof a DataTypeis provided, the symbolic name of the Noderepresenting the DataTypeshall be used.

If no components are provided, the DataType, TypeDefinition and ModellingRule columns may be omitted and only a Comment column is introduced to point to the Nodedefinition.

Components of Nodescan be complex, i.e. containing components by themselves. The TypeDefinition, NodeClass, DataTypeand ModellingRulecan be derived from the type definitions, and the symbolic name can be created as defined in 4.3.2.1. Therefore those containing components are not explicitly specified; they are implicitly specified by the type definitions.

This “OPC UA for Sercos Devices Companion Specification” is mandatory using String as IdentifierTypefor all Objects / instance NodeIdsand any NodeIds, e.g. Numeric, for the ObjectType NodeIds.

The symbolic name of each Nodedefined in this document is its BrowseName, or, when it is part of another Node, the BrowseNameof the other Node, a “.”, and the BrowseNameof itself. In this case “part of” means that the whole has a HasPropertyor HasComponent Referenceto its part. Since all Nodesnot being part of another Nodehave a unique name in this document, the symbolic name is unique.

In this “OPC UA for Sercos Devices companion specification”, the Identifierfor each Nodestarts with one out of the three possible connection / addressing types

  • Topological (defined in Sercos Communication Profile Specification).

The Sercos topology index (topological address) describes the position of a slave (device) in a Sercos network. It uses a daisy chain numeration starting with value 1 at the first slave behind the master.

  • Sercos (defined in Sercos Communication Profile Specification).

The Sercos address is a freely selectable address of a slave (device) in the range between 1 and 511. It has to be unique in the Sercos network.

  • SercosIP (defined in Sercos Internet Protocol Services Specification).

This is the IP address of a Sercos device within an IP network, e.g. Sercos network or “non-Sercos” network.

Each connection type has its own NodeId composition that can be explained as follows. Each of the following examples addresses the variable MinValuefrom parameter S-0-0001 (SercosParameterType).

Topological:

Topological,[Sercos Master No.], [Sercos Topological Address]

e.g. Topological,0,1.ParameterSet.”S-0-0001”.MinValue

Sercos:

Sercos,[Sercos Master No.], [Sercos Slave Address]

e.g. Sercos,0,1.ParameterSet.”S-0-0001”.MinValue

SercosIP:

SercosIP,[IP Address], [SlaveIndex], [SlaveExtension]

e.g. SercosIP,”192.168.0.11”,0,0.ParameterSet.”S-0-0001”.MinValue

(The SlaveIndex will be derefered to a SlaveAddress using the IDN S-0-1046. For further information please refer to the Sercos Communication Profile Specification.)

The namespace URI for Sercos Types is “http://sercos.org/UA/”.

The namespace URI for Sercos Instances is arbitrary, e.g. “http://[YourCompanyName.com]/UA/Sercos/”.

The text part of the BrowseNamesfor all Nodesdefined in this specification is specified in the tables defining the Nodes. The NamespaceIndexfor all BrowseNamesdefined in this specification is server specific and depends on the position of the namespace URI in the server NamespaceArray.

In order to access data of Sercos devices via OPC UA, data types and lengths are transformed between Sercos and OPC UA. Table 3shows the data types and data lengths transformation rules between Sercos and OPC UA.

Table 3– Transformation rules between Sercos and OPC UA

Sercos

OPC UA

Data Type

Data Length

Data Type

Extended Character Set

1 Octet List

String

Floating-Point number

4 Octet

Float

8 Octet

Double

Integer

2 Octet

Int16

4 Octet

Int32

8 Octet

Int64

Unsigned Integer

or

Binary Number

1 Octet

Byte

2 Octet

UInt16

4 Octet

UInt32

8 Octet

UInt64

Sercos Time

8 Octet

UtcTime

The Sercos list data types are transformed analogue to the single data types, e.g. S-0-0017 (Data type: Integer, Data length: 4 Octed list) is transformed to an array of Int32.