BS 7081-2-1989 Guide to construction and use of 6 30 mm (0 25 in) magnetic tape cartridge for data interchange using IMFM recording at 252 ftpmm (6400 ftpi) - Track format and meth.pdf

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1、BRITISH STANDARD BS 7081-2: 1989 ISO 8063-2: 1986 Guide to Construction and use of6.30mm(0.25in) magnetic tape cartridge for data interchange, usingIMFM recordingat 252 ftpmm(6400ftpi) Part2: Track format and method ofrecording for data interchange in start/stop mode ISO title: Information processin

2、g Data interchange on6,30mm(0.25in) wide magnetic tape cartridge using IMFM recording at252ftpmm(6 400ftpi) Part2: Track format and method of recording for data interchange in start-stop mode UDC 681.327.636:006.015.3:681.2.087:.004.12:001.4:620.1BS7081-2:1989 This British Standard, having been prep

3、ared under the directionof the Information Systems Technology Standards Policy Committee, was publishedunder the authority ofthe Board of BSI and comesintoeffect on 31 July1989 BSI 01-2000 The following BSI references relate to the work on this standard: Committee reference IST/4 Draft for comment84

4、/63328 DC ISBN 0 580 17190 6 Committees responsible for this BritishStandard The preparation of this British Standard was entrusted by the Information Systems Technology Standards Policy Committee (IST/-) to Technical Committee IST/4, upon which the following bodies were represented: Association for

5、 Payment Clearing Services British Computer Society British Telecommunications plc Business Equipment and Information Technology Association Department of Trade and Industry (National Physical Laboratory) HM Customs and Excise HM Treasury (Central Computer and Telecommunications Agency) Institute of

6、 Administrative Management Institute of Quality Assurance Institution of Electrical Engineers Institution of Electronic and Radio Engineers Institution of Mechanical Engineers National Computing Centre Ltd. Post Office Amendments issued since publication Amd. No. Date of issue CommentsBS7081-2:1989

7、BSI 01-2000 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope and field of application 1 2 Conformance 1 3 References 1 4 Data representation 1 5 Recording 1 6 Track format 2 Figure 1 1 Figure 2 1 Figure 3 2 Figure 4 3 Figure 5 3 Figure 6 4 Publications referred

8、to Inside back coverBS7081-2:1989 ii BSI 01-2000 National foreword This Part ofBS7081, prepared under the direction of the Information Systems Technology Standards Policy Committee, is identical withISO8063-2:1986 “Information processing Data interchange on6,30mm (0.25in) wide magnetic tape cartridg

9、e using IMFM recording at252ftpmm (6400ftpi) Part 2: Track format and method of recording for data interchange in start/stop mode” published by the International Organization for Standardization (ISO). The purpose of this standard is to define those characteristics necessary for successful data inte

10、rchange using magnetic tape cartridges. The information contained is intended as a guide to writing complete specifications for manufacture, purchasing and/or testing. The text of the International Standard does not accord with the recommendations for drafting product specifications given in the ISO

11、 Directives, or in BS0-3, but the BSI Technical Committee considers the text is useful as a guide when cartridges are being described or specified. For this reason this British Standard has a different title from the International Standard; it is issued as a British Standard guide, and it should onl

12、y be used as such. It should not be used on its own as a British Standard product specification and, in particular, no claims of compliance with this British Standard should be made. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards

13、 are responsible 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 646:1983 BS 4730:1985 Specification for UK7-bit coded character set (Identical, exe

14、rcising national options) ISO 2022:1986 BS 6856:1987 Specification for code extension techniques for United Kingdom7-bit and8-bit coded character sets (Identical) ISO 4341:1978 BS 5769 Specification for magnetic tape cassette and cartridge labelling and file structure, for information interchange Pa

15、rt 1:1979 Label standard version1 (Identical) ISO 4873:1986 BS 6006:1987 Specification for structure and rules for implementation of United Kingdom8-bit coded character set (Identical) ISO 8063-1:1986 BS 7081 Guide to construction and use of6.30mm (0.25in) magnetic tape cartridge for datainterchange

16、, using IMFM recording at252ftpmm (6400ftpi) Part 1:1989 Mechanical, physical and magnetic properties (Identical) Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to4, an inside back cover and a back cover. This standard has been updated (see copyri

17、ght date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS7081-2:1989 BSI 01-2000 1 1 Scope and field of application ISO8063 specifies the characteristics of a tape cartridge using6,30mm(0.25in) wide magnetic tape for data interchan

18、ge between data processing systems. ISO8063-1 specifies the dimensional, physical and magnetic characteristics of the cartridge, and the track layout. This part ofISO8063 specifies the quality of the recorded signals, and the track format to be used on a6,30mm(0.25in) magnetic tape cartridge, record

19、ed at252ftpmm(6400ftpi) using IMFM recording and the start/stop mode of operation. Together with the labelling scheme specified inISO4341,ISO8063-1 andISO8063-2 provide for full data interchange between data processing systems. NOTENumeric values in the SI and/or Imperial measurement system in this

20、part ofISO8063 may have been rounded off and therefore are consistent with, but not exactly equal to, each other. Either system may be used, but the two should be neither intermixed nor reconverted. The original design was made using the Imperial measurement system. ISO8063 applies to cartridges use

21、d for data interchange. Where it applies for testing only, this is specifically stated. 2 Conformance A 6,30mm (0.25in) wide magnetic tape cartridge shall be in conformance with ISO8063 if it meets all mandatory requirements of both ISO8063-1 and ISO8063-2. 3 References ISO 646, Information processi

22、ng ISO7-bit coded character set for information interchange. ISO 2022, Information processing ISO7-bit and8-bit coded character sets Code extension techniques. ISO 4341, Information processing Magnetic tape cassette and cartridge labelling and file structure for information interchange. ISO 4873, In

23、formation processing ISO8-bit code Structure and rules for implementation. 4 Data representation Characters shall be represented by means of the ISO7-bit coded character set (see ISO646) and, where required, by its7-bit or8-bit extensions (seeISO2022) or by means of the ISO8-bit coded character set

24、(see ISO4873). 4.1 Recording of 7-bit coded characters Each 7-bit coded character shall be recorded in bit positions B1 to B7 of an8-bit byte; bit-position B8 shall always be recorded with ZERO. The relationship shall be as shown inFigure 1. 4.2 Recording of 8-bit coded characters Each 8-bit coded c

25、haracter shall be recorded in bit positions B1 to B8 of an8-bit byte. The relationship shall be as shown inFigure 2. 5 Recording 5.1 Method of recording The method of recording shall be Inverted Modified Frequency Modulation (IMFM) for which the conditions shall be a) a flux transition shall be writ

26、ten at the centre of a bit cell containing a ZERO; b) a flux transition shall be written at the cell boundary between consecutive bit cells containing ONEs. SeeFigure 3. 5.2 Measurement All signal measurements shall be made at the point in the read chain where the amplitude is proportional to the ra

27、te of change of flux in the read head. The ratio of tape speed to the surface speed of the belt capstan shall be assumed to be exactly0,76. 5.3 Density of recording 5.3.1 The nominal recording density shall be252ftpmm (6400ftpi). The nominal bit cell length shall be3,974m (1564in). 5.3.2 The long-te

28、rm average bit cell length shall be the average bit cell length measured over at least500000 flux transitions. It shall be within 3% of the nominal bit cell length. Bits of the 7-bit combination 0 b7 b6 b5 b4 b3 b2 b1 Bit-positions in the byte B8 B7 B6 B5 B4 B3 B2 B1 Figure 1 Bits of the 8-bit combi

29、nation b8 b7 b6 b5 b4 b3 b2 b1 Bit-positions in the byte B8 B7 B6 B5 B4 B3 B2 B1 Figure 2 BS7081-2:1989 2 BSI 01-2000 5.3.3 The short-term average bit cell length, referred to a particular bit cell, shall be the average of the lengths of the preceding four bit cells. It shall be within 7% of the lon

30、g-term average bit cell length and shall be within2% of the average bit cell length of any string of128 consecutive bit cells containing the said particular bit cell. 5.4 Flux transition spacing 5.4.1 Effect of asymmetry At nominal recording density the average variation of spacing between consecuti

31、ve flux transitions, taken over32 flux transition spacings, shall not be greater than2% (seeFigure 4). 5.4.2 Effect of data patterns In each of the two possible sequences of fluxtransitions defined by bit pattern00000001000000010000000the spacing d 1between the two ZERO flux transitions preceding th

32、e ONE bit cell shall not exceed the average of the four earlier flux transition spacings by more than12%. Similarly, the spacing d 2between the two ZERO flux transitions following the ONE bit cell shall not exceed the average of the four subsequent flux transition spacings by more than12% (seeFigure

33、 5). 5.5 Signal amplitude of the interchanged cartridge 5.5.1 The average peak-to-peak signal amplitude at252ftpmm (6400ftpi) shall not deviate by more than from SRA 252 . Averaging shall be done over a minimum of6400flux transitions, which may be segmented into blocks 5.5.2 No peak-to-peak signal a

34、mplitude at126ftpmm (3200ftpi) shall be more than three times SRA 252 . 5.6 Minimum signal amplitude No cartridge, when interchanged, shall contain flux transitions the base-to-peak amplitudes of which are less than35% of half SRA 252 . 5.7 Erasure After erasure, any signal amplitude shall be less t

35、han3% of the SRA 252 . 5.8 Recording offset angle On any track the angle that a flux transition across the track makes with a line perpendicular to Reference Plane B shall not exceed9 minutes of arc. 6 Track format The layout and positioning of tracks shall be as specified in ISO8063-1. 6.1 Use of t

36、racks Each track shall be a data track and shall be written serially in the direction from the BOT marker to the EOT marker. No data for interchange shall be written between the BOT marker and the LP marker. Data for interchange shall be written after sensing the LP marker and may continue to be wri

37、tten after sensing the EW marker. Figure 3 + 50 30%BS7081-2:1989 BSI 01-2000 3 6.2 Location of characters on the tracks Each character shall be located in a byte of eight bit positions along the track numbered from1 to8 in order of recording. 6.3 Sequence of recording The least-significant bit shall

38、 be recorded first. The information to be interchanged shall be recorded serially by bit and by character. 6.4 Data block A data block shall consist of a preamble, a data portion, a CRC character and a postamble (seeFigure 6). 6.4.1 Preamble The preamble, consisting of not less than39 ZEROs and not

39、more than47 ZEROs followed by a single ONE, shall be written immediately preceding data in each data block. 6.4.2 Data portion The data portion of a data block shall contain a minimum of12 data bytes and a maximum of8192 data bytes. Figure 4 Figure 5 Bit-positions: Forward tape motion: Resulting rec

40、ording direction:BS7081-2:1989 4 BSI 01-2000 6.4.3 Cyclic Redundancy Check (CRC) The 16 bits following the data portion of a data block shall be a Cyclic Redundancy Check (CRC) character. This16-bit character shall be written in each data block following the data portion and immediately preceding th

41、e postamble, the least significant bit being recorded first. The polynomial generating the CRC shall be x 16 + x 15 + x 2 +1 6.4.4 Postamble The postamble, consisting of a ONE followed by not less than39 ZEROs and not more than47 ZEROs, shall be written immediately following the CRC in each data blo

42、ck. 6.5 Control block A control block shall consist of a preamble, two bytes of eight ZEROs, and a postamble. 6.6 Gaps 6.6.1 Integrity of gaps The gaps shall be erased. 6.6.2 Initial gap The gap between the LP marker and the first datablock shall be152,4mm min. (6inmin.) and1,2m max. (48inmax.). 6.6

43、.3 Interblock gaps The interblock gap shall have a minimum length of31mm (1.22in) and a maximum length of1,2m(48in). Any gap in excess of1,2m (48in) shall be considered as the end of data on this track. NOTEThe ability to start or stop within a gap of a given length is dependent on the tape speed se

44、lected from the range specified in ISO8063-1 sub-clause 7.5 and the acceleration and deceleration also specified in ISO8063-1 sub-clause 7.7. PREAMBLE DATA CRC POSTAMBLE 000 001 8-bit bytes one 16 bit byte 100 000 39 ZEROs minimum 12 bytes minimum 39 ZEROs minimum 47 ZEROs maximum 8196 bytes maximum

45、 47 ZEROs maximum Figure 6 BS7081-2:1989 BSI 01-2000 Publications referred to See national foreword.BS 7081-2: 1989 ISO 8063-2: 1986 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents th

46、e UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions BritishStandards are updated by amendment or revision. Users of BritishStandards should make sure that they possess the latest amendments or editions. It is the constant aim of BSI to impr

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48、967400. BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of standards. Buying standards Orders for all BSI, international and foreign standards publications should be addressed to Customer Services. Tel:02089969001

49、. Fax:02089967001. In response to orders for international standards, it is BSI policy to supply the BSI implementation of those that have been published as BritishStandards, unless otherwise requested. Information on standards BSI provides a wide range of information on national, European and international standards through its Library and its Technical Help to Exporters Service. Various BSI electronic information services are also available which give details on all its products and services. Contact the Information Centre. Tel:02089967111. Fax