1、STD*BSI BS EN bL334-b-ENGL ZOOL Lb24bb9 0933032 362 BRITISH STANDARD Distribution automation using distribution line carrier systems - Part 6: A-XDR encoding rule The European Standard EN 61334-6:2000 has the status of a British Standard ICs 29.240.99; 33.040.40 NO COPYING WITHOUT BSI PERMISSION EXC
2、EPT AS PERMITTED BY COPYRIGHT LAW BS EN IEC 61334-6:2001 6 13 34-62000 STD-BSI BS EN bL334-b-ENGL 2OOL I Lb24bb9 0713033 2T9 W BS EN 61334-6:2001 Amd. No. National foreword Date Comments This British Standard is the official English language version of EN 61334- 6:2000. It is identical with IEC 6133
3、4-6:2000. The UK participation in its preparation was entrusted to Technical Committee PELA57, Power system control and associated communications, which has the responsibility to: - - aid enquirers to understand the text; present to the responsible internationalEuropean committee any enquiries on th
4、e interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. - A list of organizations represented on this committee can be obtained on request to its secretary. From i January 1997, all IEC publ
5、ications have the number 60000 added to the old number. For instance, IEC 27-1 has been renumbered as IEC 60027-1. For a period of time during the change over from one numbering system to the other, publications may contain identifiers from both systems. Cross-references Attention is drawn to the fa
6、ct that CEN and CENELEC Standards normally include an annex which lists normative references to international publications with their corresponding European publications. The British Standards which implement these international or European publications may be found in the BSI Standards Catalogue un
7、der the section entitled “International Standards Correspondence Index”, or by using the “Find facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct a
8、pplication. Compliance with a British Standard does not of itself confer immunity from legal obligations. This British Standard, having been prepared under the direction of the Electrotechnical Sector Committee, was published under the authority of the Standards Committee and comes into effect on 15
9、June2001 I O BSI 06-2001 Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 39 and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. ISBN O 580 37387 8 STD-BSI BS EN bL334-b-ENGL 2001
10、 m Lb24bb9 0933034 L35 m EUROPEAN STANDARD EN 61334-6 NORME EUROPENNE EUROPISCHE NORM November 2000 ICs 29.240.20;33.200 English version Distribution automation using distribution line carrier systems Part 6: A-XDR encoding rule (IEC 61 334-6:ZOOO) Automatisation de la distribution Verteilungsautoma
11、tisierung laide de systmes de communication courants porteurs Verteilungsleitungen Partie 6: Rgles dencodage A-XDR mit Hilfe von Trgersystemen auf Teil 6: A-XDR-Codierungsregel (CE1 61 334-6:ZOOO) (IEC 61 334-62000) This European Standard was approved by CENELEC on 2000-08-01. CENELEC members are bo
12、und to comply with the CENICENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Uptodate lists and bibliographical references concerning such national standards may be obtained on application to the Ce
13、ntral Secretariat or to any CENELEC member. This European Standard exists in three oficial versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same s
14、tatus as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CENELEC Euro
15、pean Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels O 2000 CENELEC - All rights of exploltation in any form and by any means reserved worldwide
16、for CENELEC members. Ref. No. EN 61334-6:2000 E STD.BS1 BS EN bL334-b-ENGL 2001 M Lb24bb7 0733035 073 M Page 2 BS EN 61334-6:2000 Foreword The text of document 57/451/FDIS, future edition 1 of IEC 61334-6, prepared by IEC TC 57, Power system control and associated communications, was submitted to th
17、e IEC-CENELEC parallel vote and was approved by CENELEC as EN 61334-6 on 2000-08-01. The following dates were fixed: - latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement - latest date by which the national standards
18、conflicting with the EN have to be withdrawn (dop) 2001-05-01 (dow) 2003-08-01 Annexes designated “normative“ are pari of the body of the standard. Annexes designated “informative“ are given for information only. In this standard, annex ZA is normative and annexes A, B and C are informative. Annex Z
19、A has been added by CENELEC. Endorsement notice The text of the International Standard IEC 61334-6:2000 was approved by CENELEC as a European Standard without any modification. . . . STDaBSI BS EN 61334-6-ENGL 2001 6 1624669 0913036 TOA 6 Page 3 BS EN 61334-62000 CONTENTS Page INTRODUCTION 4 Clause
20、Scope and object . 5 Normative references . 5 General characteristics of A-XDR . 6 Structure of an encoding 6 Rules for encoding . 9 5.1 The Identifier field . 9 5.2 The Length field . 10 5.3 The Contents field 10 Encoding procedures 11 Encoding of a BOOLEAN value 14 Encoding of an ENUMERATED value
21、. 15 Encoding of a BIT STRING value . 15 Encoding of an BYTE STRING value 17 Tagged types (implicit, explicit and ASN.l explicit tagging) . 19 OPTIONAL and DEFAULT components 21 Encoding of a SEQUENCE value 22 Encoding of a SEQUENCE OF value 23 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 6.1 1 Encoding
22、 of the VisibleString type 25 6.12 Encoding of the GeneralizedTime type . 26 6.13 Encoding of the ASN.l NULL typehalue . 26 Encoding of an INTEGER value 11 Encoding of a CHOICE value . 18 Annex A (informative) Extensibility 27 Annex B (informative) ASN.l types and keywords used in DLMS . 28 Annex C
23、(informative) Examples of A-XDR encoding for DLMS PDUs . 29 Annex ZA (normative) Normative references to international publications with their corresponding European publications 39 Figure 1 . The basic BER structure 6 Figure 2 . The structure of a constructed BER encoding . 7 Figure 3 . The structu
24、re of a constructed A-XDR encoding . 7 Figure 4 - Structure of the variable-length integer encoding . 13 O BSI 06-2001 . STD.BS1 BS EN bL334-6-ENGL 2001 E Lb24669 0733037 944 Page 4 BS EN 61334-6:2000 I NTRO D U CTION ITU-T Recommendation X.208 specifies a formal language (ASN.l = Abstract Syntax No
25、tation One) which enables application layer specifications to define the typesl) of information they need to exchange. A representation of this information can be derived by applying a set of encoding rules to values of types defined using the ASN.l notation. Application of these encoding rules prod
26、uces a transfer syntax for such values. Although many such sets of encoding rules could be imagined, for a long time only one single set - the BER = Basic Encoding Rules - has been standardized (see ITU-T Recommendation X.209). This is mainly because BER is quite adequate for a wide range of applica
27、tions. On the other hand, in some particular cases, BER can obviously be redundant. Avoiding this redundancy by providing alternative encoding rules for those particular cases is the scope of some recently developed new transfer syntax standards (DER, CER, PER). Clearly, the aim is not to provide ge
28、neral-purpose, but rather specialized, alternatives to the BER, which are more suitable than the BER in some respects. Contrary to these general-purpose encoding rules, this standard specifies a new, special- purpose set of encoding rules - A-XDR - which fits in best with the DLMS context (see IEC 6
29、1334-4-41). The principal objective is to encode DLMS PDUs in such a way that the PDUs byte count and encoding/decoding complexity - the length of the required code, its processing performance and time - are optimizedz). This objective is fulfilled by two basic principles. a) A-XDR specifies encodin
30、g rules only for a subset of ASN.l types: for the subset which is used for the DLMS specification. (That is why A-XDR is special-purpose.) b) A-XDR specifies byte-oriented encoding rules. 1) ASN.l also specifies a notation for the specification of the value of a defined type 2) With respect to the P
31、DU size only, PER over-performs A-XDR. However, this better compacting performance - the principal objective of PER - is achieved by a much more extensive use of bit fields instead of byte fields to encode different values. To reduce encoding sizes further, the more complex PER variant (the Unaligne
32、d PER) also benefits from the limitation of values of constrained types. Gain on compactness is thus obtained at the expense of computational overhead. Furthermore, PER comes with two, incompatible variants (Aligned and Unaligned), and it is recommended that implementations should support both of th
33、em. This complexity means that PER is not optimal for the DLMS context. The lighter-weight A-XDR encoding rules are more suitable to that simple environment, which is in some cases very poor in resources. O BSI 06-2001 STD-BSI BS EN bL334-6-ENGL 2003 - Lb24bb9 0933038 provide optimal4) encoding for
34、DLMS PDUs. NOTE Provided that A-XDR ensures optimal encoding for DLMS PDUs, it is intended to be the default encoding rule 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
35、 the given protocol (for example, IEC 61334-4-42), as part of the Application context. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this part of IEC 61 334. For dated references, subsequent amendments to,
36、or revisions of, any of these publications do not apply. However, parties to agreements based on this part of IEC 61334 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the nor
37、mative document referred to applies. Members of IS0 and IEC maintain registers of currently valid International Standards. IEC 61 334-4-41 : 1996, Distribution automation using distribution line carrier systems - Pari 4: Data communication protocols - Section 4 I: Application protocols - Distributio
38、n line message specification IEC 61 334-4-42:1996, 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 pack
39、ed encoding rules (PER) ITU-T Recommendation X.208:1988, Specification of Abstract Syntax Notation One (ASN. 7) ITU-T Recommendation X.209:1988, Specification of basic encoding rules for Abstract Syntax Notation One (ASN. I) 3) A-XDR stands for Adapted XDR. In fact, these encoding rules are derived
40、from a proven and de facto standard of the Unix world, called XDR (external Data Representation, rfclOl4). 4) See footnote 2 of the introduction. O BSI 06-2001 STD-BSI BS EN bL334-b-ENGL 2OOL E Lb24bb9 0933039 7L7 E Page 6 BS EN 61334-6:2000 3 General characteristics of A-XDR A-XDR specifies encodin
41、g rules which can be used to encode and decode the values of an abstract syntax defined as the values of a single ASN.l type (the outermost type). This single ASN.1 type is either a simple type or a composite type. A component of a composite type may be a simple type or a composite type itself. The
42、A-XDR encoding rules exploit the fact that the sender and the receiver of a DLMS PDU are operating exactly the same specification of the abstract syntax. While with BER the encoding of every value of any type of abstract syntax is constructed in type-length-value (TLV) style, A-XDR encodes the type
43、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 determine the structure of the encoding. NOTE This encoding method gives the result that A-XDR encoding rules are not extensible (see annex A).
44、In order to keep A-XDR as simple as possible, some restrictions apply with respect to the abstract syntax to be encoded as follows: 0 0 A-XDR specifies byte-oriented encoding rules. This means that each part of the encoding - and therefore also the encoding of the whole - is an integral number of by
45、tes. no encoding support is provided for ASN.l types which are not used in DLMSS); the CHOICE ASN.l type should contain only explicitly6) tagged components. 4 Structure of an encoding The basis of BER encoding (see ITU-T Recommendation X.209) is a structure, made up of three parts: type, length and
46、value, as shown in figure 1. In BER, these three parts are termed identifier (I), length (L) and contents (C). The identifier part identifies the type, the length part allows the end of the contents71 to be found, and the contents part conveys one of the possible values of that type. I Identifier Le
47、ngth Contents I IEC 730/2000 Figure 1 - The basic BER structure The contents field can be simply a series of byte) (primitive encoding) or a series of nested encoding (constructed encoding), as shown in figure 2. 5) Annex B enumerates the ASN.l types and keywords which are used in the DLMS specifica
48、tion. 6) The terms “explicit tagging“ and “implicit tagging“ have a slightly different meaning in A-XDR than that specified for ASN.l and BER. Subclause 6.7 deals with these notions and also introduces the new “ASN.1 explicit tagging“ term. 7) In fact, for BER, the length field does not always liter
49、ally represent the length of the contents. BER specifies two forms (definite and indefinite) of the length field. Although, when the definite form is used, the length field effectively represents the number of bytes in the contents field, for the indefinite form the length field indicates that the contents are terminated by end-of-contents bytes. 8) Zero or more. O BSI 06-2001 STD.BSI BS EN bL334-b-ENGL 2003 H Lb24bb9 0933040 439 = Page 7 BS EN 61334-62000 I I l c2 I I c1 IEC 731/2000 Figure 2 - The structure of a constructed BER encoding The nesting can be as de
