IEC 61334-6-2000 pdf free download – Distribution automation using distribution line carrier systems – Part 6: A-XDR encoding rule.
This part of lEC 61334 defines a set of encoding rules – the A-XDR3) encoding rules – thatmay be used to derive the specification of a transfer syntax for values of types defined in theDLMS core standard using the ASN.1 notation (see lEc 61334-4-41).These A-XDR encodingrules are also to be applied for decoding such a transfer syntax in order to identify the datavalues being transferred.
The A-XDR encoding rules
.are used at the time of communication;.provide optimal4) encoding for DLMS PDUs.
NOTE Provided that A-XDR ensures optimal encoding for DLMS PDUs,it is intended to be the default encodingrule for DLMS-based communication protocols.Nevertheless, the default – and also the possibly usable optional -encoding rules will be specified in the Application Layer document of the given protocol (for example,IEC 61334-4-42),as part of the Application context.
Normative references
The following normative documents contain provisions which，through reference in this text,constitute provisions of this part of lEC 61334.For dated references,subsequent amendmentsto,or revisions of，any of these publications do not apply. However，parties to agreementsbased on this part of iEC 61334 are encouraged to investigate the possibility of applying themost recent editions of the normative documents indicated below.For undated references, thelatest edition of the normative document referred to applies.Members of lS0 and lEC maintainregisters of currently valid lnternational Standards.
IEC 61334-4-41:1996,Distribution automation using distribution line carrier systems – Part 4:Data communication protocols – Section 41: Application protocols – Distribution line messagespecification
IEC 61334-4-42:1996,Distribution automation using distribution line carrier systems – Part 4:Data communication protocols – Section 42: Application protocols – Application layer
ISO/IEC 8825-2:1997,Information technology – ASN.1 Encoding rules: Specification of packedencoding rules (PER)
ITU-T Recommendation X.208:1988，Specification of Abstract Syntax Notation One (ASN.1)
ITU-T Recommendation X.209:1988,Specification of basic encoding rules for Abstract SyntaxNotation One (ASN.1 )
3General characteristics of A-XDR
A-XDR specifies encoding rules which can be used to encode and decode the values of anabstract syntax defined as the values of a single ASN.1 type (the outermost type).This singleASN.1 type is either a simple type or a composite type. A component of a composite type maybe a simple type or a composite type itself.
The A-XDR encoding rules exploit the fact that the sender and the receiver of a DLMS PDU areoperating exactly the same specification of the abstract syntax.While with BER the encoding ofevery value of any type of abstract syntax is constructed in type-length-value (TLV) style,A-XDR encodes the type and the length of the value only when this information is necessary.This implies that without knowledge of the type of value encoded it is not possible to determinethe structure of the encoding.
NOTE This encoding method gives the result that A-XDR encoding rules are not extensible (see annex A),
ln order to keep A-XDR as simple as possible，some restrictions apply with respect to theabstract syntax to be encoded as follows:
.no encoding support is provided for ASN.1 types which are not used in DLMS5);. the CHOICE ASN.1 type should contain only explicitly6) tagged components.
A-XDR specifies byte-oriented encoding rules. This means that each part of the encoding – andtherefore also the encoding of the whole – is an integral number of bytes.
4 Structure of an encoding
The basis of BER encoding (see lTU-T Recommendation X.209) is a structure， made up ofthree parts: type, length and value， as shown in figure 1.In BER, these three parts are termedidentifier (l), length(L) and contents (C).The identifier part identifies the type，the length partallows the end of the contents7) to be found, and the contents part conveys one of the possiblevalues of that type.IEC 61334-6 pdf download.