ISO/IEC 15757:1998

INTERNATIONAL ISO/IEC
STANDARD 15757
First edition
1998-07-15
Information technology — Data interchange
on 8 mm wide magnetic tape cartridge —
Helical scan recording — DA-2 format
Technologies de l'information — Échange de données sur cartouche de
bande magnétique de 8 mm de large — Enregistrement par balayage en
spirale — Format DA-2
Reference number
B C
Contents
Section 1 - General 1
1 Scope 1
2 Conformance 1
2.1 Magnetic tape cartridges 1
2.2 Generating drive 1
2.3 Receiving drive 1
3 Normative references 1
4 Definitions 1
4.1 a.c. erase: 2
4.2 algorithm 2
4.3 append point 2
4.4 Average Signal Amplitude 2
4.5 azimuth 2
4.6 back surface 2
4.7 bit cell 2
4.8 byte 2
4.9 cartridge 2
4.10 Channel bit 2
4.11 Cluster 2
4.12 Cyclic Redundancy Check (CRC) character 2
4.13 Digital Sum Variation (DSV) 2
4.14 Error Correcting Code (ECC) 2
4.15 File Mark 2
4.16 flux transition spacing 2
4.17 Logical Beginning of Partition (LBOP) 2
4.18 Logical Block 2
4.19 magnetic tape 2
©  ISO/IEC 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or
utilized in any form or by any means, electronic or mechanical, including photocopying and micro-
film, without permission in writing from the publisher.
ISO/IEC Copyright Office • Case postale 56 • CH-1211 Genève 20 • Switzerland
Printed in Switzerland
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ISO/IEC ISO/IEC 15757:1998 (E)
4.20 Master Standard Reference Tape 2
4.21 Partition 2
4.22 Physical Beginning of Partition (PBOP) 2
4.23 Physical Beginning of Tape (PBOT) 2
4.24 Physical End of Partition (PEOP) 2
4.25 Physical End of Tape (PEOT) 2
4.26 physical recording density 2
4.27 Read Back Check (RBC) 2
4.28 Reference Field 2
4.29 Secondary Standard Reference Tape (SSRT) 2
4.30 Set Mark 3
4.31 Standard Reference Amplitude (SRA) 3
4.32 Standard Reference Current (Ir) 3
4.33 Tape Reference Edge 3
4.34 Test Recording Current (TRC) 3
4.35 Track 3
4.36 Typical Field 3
5 Conventions and Notations 3
5.1 Representation of numbers 3
5.2 Names 3
5.3 Reserved fields 3
6 Acronyms 3
7 Environment and Safety 4
7.1 Testing environment 4
7.2 Operating environment 4
7.3 Storage environment 4
7.4 Transportation 4
7.5 Safety 4
7.6 Flammability 4
Section 2 - Requirements for the case 5
8 Dimensional and mechanical characteristics of the case 5
8.1 General 5
8.2 Overall dimension 5
8.3 Holding areas 6
8.4 Cartridge insertion 6
8.5 Window 7
8.6 Loading grips 7
8.7 Label areas 7
8.8 Datum areas and datum holes 7
8.9 Support areas 8
8.10 Recognition holes 9
8.11 Write-inhibit hole 9
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ISO/IEC
8.12 Pre-positioning surfaces 10
8.13 Cartridge lid 10
8.14 Cartridge reel lock 11
8.15 Reel access holes 12
8.16 Interface between the reels and the drive spindles 12
8.17 Light path 13
8.18 Position of the tape in the case 14
8.19 Tape path zone 14
8.20 Tape access cavity 14
8.21 Tape access cavity clearance requirements 15
Section 3 - Requirements for the Unrecorded Tape 31
9 Mechanical, physical and dimensional characteristics of the tape 31
9.1 Materials 31
9.2 Tape length 31
9.2.1 Length of magnetic tape 31
9.2.2 Length of leader and trailer tapes 31
9.2.3 Splicing tape 31
9.3 Width 31
9.3.1 Width of magnetic, leader and trailer tape 31
9.3.2 Width and position of splicing tape 31
9.4 Discontinuities 31
9.5 Thickness 31
9.5.1 Thickness of magnetic tape 31
9.5.2 Thickness of leader and trailer tape 31
9.5.3 Thickness of splice tape 31
9.6 Longitudinal curvature 32
9.7 Cupping 32
9.8 Coating adhesion 32
9.9 Layer-to-layer adhesion 33
9.10 Tensile strength 33
9.10.1 Breaking strength 33
9.10.2 Yield strength 33
9.11 Residual elongation 33
9.12 Electrical resistance of the recording surface 34
9.13 Tape winding 34
9.14 Light transmittance of tape 34
9.15 Data cartridge recognition stripe 34
10 Magnetic recording characteristics 35
10.1 Test conditions 35
10.2 Typical Field 35
10.3 Signal Amplitude 35
10.4 Resolution 35
10.5 Narrow-band Signal-to-Noise Ratio 36
10.6 Ease of erasure 36
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ISO/IEC ISO/IEC 15757:1998 (E)
10.7 Tape quality 36
10.7.1 Missing pulses 36
10.7.2 Missing pulse zone 36
10.7.3 Overwrite 36
Section 4 - Requirements for an Interchanged Tape 37
11 Format of a track pair 37
11.1 General 37
11.2 Physical block format 38
11.2.1 General 38
11.2.2 Common header fields 39
11.2.3 Data Block 40
11.2.4 Erase Block 41
11.2.5 Diagnostic Block 41
11.2.6 Physical Beginning of Partition (PBOP) Block 41
11.2.7 Long File Mark Block 42
11.2.8 Short File Mark Block 42
11.2.9 Logical Beginning of Partition (LBOP) Block 43
11.2.10 Set Mark Block 44
11.2.11 Gap Block 45
11.2.12 End of Data (EOD) Block 45
11.2.13 Recorded patterns 45
11.3 Search field format 46
11.3.1 Search field data 46
11.3.2 Search field ECC 47
11.3.3 Search field recording patterns 48
11.4 Servo area 49
11.5 Track layout 50
12 Method of recording 51
12.1 Physical Recording Density 51
12.1.1 Long Term Average Bit Cell Length 51
12.1.2 Short Term Average Bit Cell Length 52
12.1.3 Rate of Change 52
12.2 Bit Shift 52
12.3 Amplitude of Data Signals 52
13 Track geometry 52
13.1 General 52
13.2 Average track pitch - C 52
13.3 Track pitch variation 53
13.4 Track width - B 53
13.5 Track angle - A 53
13.6 Track length -E 53
13.7 Guard band - F 53
13.8 Azimuth angles 53
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13.9 Track linearity 53
14 Layout of a tape 53
14.1 General 53
14.2 Tape History Log (THL) 54
14.3 Physical Beginning of Partition 54
14.4 Logical Beginning of Partition 54
14.5 Data area 54
14.5.1 General 54
14.5.2 Short File Mark 54
14.5.3 Long File Mark 54
14.5.4 Set Mark 54
14.6 End of Data 54
14.7 Physical End of Partition (PEOP) 54
Annexes
A - Measurement of Light Transmittance of Tape and Leaders 55
B - Measurement of bit shift 58
C - Representation of 8-bit bytes by 10-bit patterns 60
D - Generation of Data Area CRC 67
E - Generation of ECC 68
F - Generation of Logical Block CRC 70
G - Generation of Hamming Code ECC 71
H - Generation of Search Field CRC 72
J - Randomization 73
K - Recommendations for transportation 74
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ISO/IEC ISO/IEC 15757:1998 (E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the
specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in the
development of International Standards through technical committees established by the respective organization to deal with
particular fields of technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other
international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the work.
In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1. Draft
International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the national bodies casting a vote.
International Standard ISO/IEC 15757 was prepared by ECMA (as ECMA-249) and was adopted, under a special “fast-track
procedure”, by Joint Technical Committee ISO/IEC JTC 1, Information technology, in parallel with its approval by national
bodies of ISO and IEC.
Annexes A to J form an integral part of this International Standard. Annex K is for information only.
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
INTERNATIONAL STANDARD ISO/IEC ISO/IEC 15757:1998 (E)
Information technology — Data interchange on 8 mm wide magnetic tape
cartridge — Helical scan recording — DA-2 format
Section 1 - General
1Scope
This International Standard specifies the physical and magnetic characteristics of a 8 mm wide magnetic tape cartridge to
enable physical interchange of such cartridges between drives. It also specifies the quality of the recorded signals, the recording
method and the recorded format, thereby allowing data interchange between drives by means of such magnetic tape cartridges.
Information interchange between systems also requires, at a minimum, agreement between the interchange parties upon the
interchange code(s) and the specifications of the structure and labelling of the information on the interchanged cartridge.
2 Conformance
2.1 Magnetic tape cartridges
A magnetic tape cartridge shall be in conformance with this International Standard if it satisfies all mandatory requirements of
this International Standard throughout the extent of the tape.
2.2 Generating drive
A drive generating a magnetic tape cartridge for interchange shall be entitled to claim conformance with this International
Standard if all the recordings that it makes on a tape meet the mandatory requirements of this International Standard. A claim
of conformance shall state whether or not one or more registered compression algorithm(s) are implemented within the system
to process data from the host prior to allocating data to physical blocks.
2.3 Receiving drive
A system receiving a magnetic tape cartridge for interchange shall be entitled to claim conformance with the International
Standard if it is able to handle any recording on this tape according to this International Standard. A receiving drive shall be
able to recognize the use of a data compression algorithm and make the algorithm registration number available to the host.
3 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this International
Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to
agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent
editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International
Standards.
ISO 527-1:1993, Plastics — Determination of tensile properties — Part 1: General principles.
ISO 1302:1992, Technical drawings — Method of indicating surface texture.
ISO/IEC 11576:1995, Information technology — Procedure for the registration of algorithms for the lossless compression
of data.
IEC 950:1991, Safety of information technology equipment.
4 Definitions
For the purposes of this International Standard, the following definitions apply.

ISO/IEC
4.1 a.c. erase: A process of erasure utilizing alternating magnetic fields of decaying intensity.
4.2 algorithm: A set of rules for transforming the logical representation of data.
4.3 append point: The first physical block on the first track 1 following the two gap stripes that precede a Long File
Mark, Set Mark, or EOD and follow the last track pair containing any portion of a logical block
4.4 Average Signal Amplitude: The average peak-to-peak value of the signal of a read head measured over a
minimum of 3 000 flux transitions, exclusive of missing pulses.
4.5 azimuth: The angular deviation, in degrees of arc, of the recorded flux transitions on a track from a line normal to
the track centreline.
4.6 back surface: The surface of the tape opposite to the magnetic coating used to record data.
4.7 bit cell: A distance along the track allocated for the recording of a channel bit.
4.8 byte: An ordered set of bits acted upon as a unit.
4.9 cartridge: A case containing magnetic tape stored on twin reels.
4.10 Channel bit: A bit after 8-10 transformation.
4.11 Cluster: A group of sequential blocks of the same block type.
4.12 Cyclic Redundancy Check (CRC) character: A character derived from information contained in data
bytes that are used for error detection.
4.13 Digital Sum Variation (DSV): The integrated value of Channel bits taken from the beginning of each track
counting a ONE as +1 and a ZERO as -1.
4.14 Error Correcting Code (ECC): A mathematical procedure yielding bytes used for the detection and
correction of errors.
4.15 File Mark:
A mark recorded on the tape at the request of the host system to separate files or to provide a splice
point. This format provides for Long or Short File Marks.
4.16 flux transition spacing: The distance along a track between successive flux transitions.
4.17 Logical Beginning of Partition (LBOP): The point in a partition where a recording of data for
interchange commences.
4.18 Logical Block: Information (data, file marks, or set marks) sent from the host to the tape drive to be recorded.
4.19 magnetic tape: A tape that accepts and retains magnetic signals intended for input, output, and storage of data
for information processing.
4.20 Master Standard Reference Tape: A tape selected as the standard for Signal Amplitude, Typical Field,
Overwrite and Resolution.
NOTE - The Master Standard Reference Tape has been established by Pericomp Corporation.
4.21 Partition: A formatted length of tape used to record data. Partitions are used to divide the tape into shorter
updatable areas.
4.22 Physical Beginning of Partition (PBOP): The point along the length of tape at which a partition begins.
4.23 Physical Beginning of Tape (PBOT): The transition from the tape leader to the opaque area of the splice
by which the translucent leader tape is joined to the magnetic tape.
4.24 Physical End of Partition (PEOP): The point along the length of tape at which a partition ends.
4.25 Physical End of Tape (PEOT): The transition from the opaque area of the splice to the translucent trailer
tape.
4.26 physical recording density: The number of recorded flux transitions per unit length of track, expressed in
flux transitions per millimetre (ftpmm).
4.27 Read Back Check (RBC): A Read Back Check occurs when, while writing, the data is read by trailing heads
and checked for errors.
4.28 Reference Field: The Typical Field of the Master Standard Reference Tape.
4.29 Secondary Standard Reference Tape (SSRT): A tape the performance of which is known and stated in
relation to that of the Master Standard Reference Tape.
NOTE - Secondary Standard Reference Tapes can be ordered under the Part Number SSRT/M.AME/PC97, from Pericomp Corporation, 14 Huron Drive,
Natick, MA 01760, USA.
ISO/IEC ISO/IEC 15757:1998 (E)
In principle, such tapes will be available for a period of 10 years from the first edition of this International Standard. However, by agreement between
ISO/IEC JTC 1 and Pericomp, this period may be shortened or extended to take account of demand for such tapes.
It is intended that these be used for calibrat
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