1、BRITISH STANDARD BS 4505-3: 1981 ISO 1155-1978 Digital data transmission Part 3: Method for use of longitudinal parity to detect errors in information messages ISO title: Information processing Use of longitudinal parity to detect errors in information messages UDC 681.327.8BS4505-3:1981 This Britis
2、h Standard, having been prepared under the directionof the Data ProcessingStandards Committee,was published underthe authority of the Board ofBSI and comes into effect on 30November1981 BSI 03-1999 First published September 1969 First revision November 1981 The following BSI references relate to the
3、 work on this standard: Committee reference OIS/6 Draft for comment 81/60119 DC ISBN 0 580 12372 3 Cooperating organizations The Data Processing Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following: British Computer Society Ltd
4、.* British Paper and Board Industry Federation (PIF) British Printing Industries Federation Business Equipment Trade Association* Central Computer and Telecommunications Agency (Civil Service Department)* Committee of London Clearing Bankers on behalf of the Committee of Scottish Clearing Bankers, C
5、o-operative Bank, Central Trustee Savings Bank and Yorkshire Bank* Department of Industry (Computers, Systems and Electronics) Department of Industry (National Physical Laboratory)* Electricity Supply Industry in England and Wales* Government Communications Headquarters HM Customs and Excise Institu
6、te of Cost and Management Accountants Institute of Purchasing and Supply Institution of Electrical Engineers Inter-university Committee on Computing London Transport Executive National Computer Users Forum National Computing Centre Ltd.* National Research Development Corporation Post Office* Society
7、 of British Aerospace Companies Limited The organizations marked with an asterisk in the above list, together with the following, were directly represented on the Technical Committee entrusted with the preparation of this British Standard: British Airways British Electrical and Allied Manufacturers
8、Association (BEAMA) British Gas Corporation British Railways Board Business Equipment Trade Association Civil Aviation Authority Engineering Equipment Users Association Ministry of Defence Telecommunication Engineering and Manufacturing Association (TEMA) Amendments issued since publication Amd. No.
9、 Date of issue CommentsBS4505-3:1981 BSI 03-1999 i Contents Page Cooperating organizations Inside front cover National foreword ii 0 Introduction 1 1 Scope and field of application 1 2 Rules for generating the longitudinal parity block check character 1 Publications referred to Inside back coverBS45
10、05-3:1981 ii BSI 03-1999 National foreword This British Standard, prepared under the direction of the Data Processing Standards Committee, is identical with ISO1155-1978, “Information processing Use of longitudinal parity to detect errors in information messages” published by the International Organ
11、ization for Standardization (ISO). This British Standard supersedes BS4505-3:1969 which is now withdrawn. Terminology and conventions. The text of the international standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain convention
12、s are not identical with those used in British Standards; attention is especially drawn to the following. Wherever the words “International Standard” appear, referring to this standard, they should be read as “British Standard”. A related British Standard for ISO1177-1973 is BS4505 “Digital data tra
13、nsmission” Part2:1969 “Character structure for start/stop and synchronous transmission”. It refers to the United Kingdom7-bit data code rather than the ISO7-bit code. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible
14、 for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International standard Corresponding British Standard ISO 646-1973 BS 4730:1974 Specification for the United Kingdom7-bit data code (ISO-7-UK) (Technically e
15、quivalent) a ISO 1745-1975 BS 4505 Digital data transmission Part1:1981 Specification for basic mode control procedures (Identical) a BS 4730 contains the basic code table and the International Reference Version of the ISO7-bit code in addition to the United Kingdom7-bit data code. Summary of pages
16、This document comprises a front cover, an inside front cover, pages i and ii, pages1 and 2, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cover.BS45
17、05-3:1981 BSI 03-1999 1 0 Introduction In data communication systems the information formats and the redundancy in the data to be transmitted differ widely from one application to another. It is therefore clear that a number of classes of error protection systems may be required. This International
18、Standard defines one method of error detection which satisfies a wide range of applications. It consists of accompanying the data block or text by one checking character (in addition to character parity) and it is often referred to as the “Longitudinal Parity Method”. 1 Scope and field of applicatio
19、n This International Standard specifies a method for detecting errors in information messages by attaching one block check character to the transmitted information block (or text) and checking this character when it is received. The method of correcting errors when they are detected is subject to th
20、e particular application and is performed at a higher level. The method is applicable to systems which use the7-bit coded character set which is the subject of ISO646, 7-bit coded character set for information processing interchange, and the basic mode of implementing this7-bit code in data communic
21、ation systems, which is the subject of ISO1745, Information processing Basic mode control procedures for data communication systems. The rules for generating the character parity bits, according to ISO1177, Information processing Character structure for start/stop and synchronous transmission, are t
22、hat the character parity sense shall be odd in synchronous systems and even in asynchronous systems. 2 Rules for generating the longitudinal parity block check character 2.1 Block check character 2.1.1 The block check character shall be composed of7 bits plus a parity bit. 2.1.2 Each of the first7 b
23、its of the block check character shall be the modulo2 binary sum of every element in the same bit1 to bit7 column of the successive character of the transmitted block. 2.1.3 The longitudinal parity of each column of the block, including the block check character, shall be even. 2.1.4 The sense of th
24、e parity bit of the block check character shall be the same as for the information characters (odd for synchronous transmission, even for asynchronous transmission). 2.2 Summation 2.2.1 The summation to obtain the block check character shall be started by the first appearance of either SOH (Start of
25、 Heading) or STX (Start of Text). 2.2.2 The starting character shall not be included in the summation. 2.2.3 If an STX character appears after the summation has been started by SOH, then the STX character shall be included in the summation as if it were a text character. 2.3 With the exception of SY
26、N (Synchronous Idle), all the characters which are transmitted after the start of the block check summation shall be included in the summation, including the ETB (End of Transmission/Block) or ETX (End of Text) control character which signals that the next following character is the block check char
27、acter. 2.4 No character, SYN or otherwise, shall be inserted between the ETB or ETX character and the block check character.2 blankBS4505-3:1981 BSI 03-1999 Publications referred to See national foreword.BSI 389 Chiswick High Road London W4 4AL | | | | | | | | | | | | | | | | | | | | | | | | | | | |
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