1、INTERNATIONAL STANDARD ISO/IEC 8441-2 First edition 1991-08-01 Information technology - High density digital recording (HDDR) - Part 2: Guide for interchange practice Technologies de /information -.- Enregistrement numCrique 9 haute densite (HDDR) - Par-tie 2: Guide pour /change dinformation Referen
2、ce number ISOllEC 8441-2:1991(E) ISOllEC 8441-2:1991(E) Contents Page 1 Scope . . . . . . . _._._._._._._,_._., 1 2 Normative references _._,.,.,.,._._,._.,_.,_ ,.,.,_ 1 3 Definitions . . . . _._._._._._._._. 1 4 Recording and reproducing characteristics . . . . . . . . . . . . . . . . . . . . . . .
3、 _. 4 4.1 General ,._._,_._. 4 4.2 Tape speeds . . . . . . . . _._._._._._._._. 4 4.3 Track configurations ,_._._,.,._.,.,._.,.,._.,. 5 4.4 Recorder/reproducer characteristics . . . . . . . . . . . . . 5 4.5 Other characteristics _._,.,._._._.,_.,._.,_,._,._._., 6 5 Methods for high density digital
4、recording _._._,_. 15 5.1 Introduction ._._,._,_;._._._._._._._._ 15 5.2 Record transfer function . . . . . . . . . . . _ 15 5.3 Flux transition densities and rates for high density recording 15 5.4 Data input/output ._,.,_,_.,._,_._._._. ._._ 16 5.5 Data sense ,_.,.,._.,.,_.,.,., 16 5.6 Reproduce e
5、qualization _.,_._.,., 16 5.7 Other system parameters ,_,_,.,._._., 17 0 ISOllEC 1991 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission In writing from the pub
6、lisher. ISOllEC Copyright Office l Case Postale 56 l CH-1211 GenBve 20 l Switzerland Prlnted in Switzerland ii ISOllEC 8441-2:1991(E) 5.8 Auxiliary data recording _._,_._,_._,._. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Annexes A Operating modes, performance categories, and cross-p
7、lay criteria for high density PCM recording systems . 18 A.1 Performance categories _._._. 18 A.l.l General _._._._._._,_. 18 A.1.2 Record head gap length for category A and category B performance 18 A.1.3 Record head gap length for category C performance 18 A.1.4 Operating modes 19 A.2 Single track
8、 serial high density recording 19 A.2.1 Serial high density recording with wideband analogue recorder/reproducer (category A) . 19 A.2.2 Parallel high density digital recording 21 B Recording techniques 22 B.1 Recording code names and their abbreviations 22 8.2 Enhanced NRZ format for parallel HDDR
9、. 22 8.2.1 ENRZ coding 22 8.2.2 ENRZ - parallel HDDR format 22 B-2.3 Summary of enhanced NRZ format 22 8.3 Miller squared format (M2) for parallel HDDR . . . . . . . . . . . . . -. 23 8.3.1 Miller squared coding 23 B-3.2 MJ format for parallel HDDR 23 8.3.3 Summary of M2 format . 24 B.3.4 M* format
10、bandwidth utilization/packing density 24 8.4 Randomized NRZ-L format parallel HDDR . 24 8.4.1 RNRZ-L coding . 24 8.4.2 RNRZ-L parallel HDDR format . 24 8.4.3 Summary of randomized NRZ-L format 25 8.4.4 Randomized NRZ-L format bandwidth utilization/packing density . _._._,_,.,_._._._._._._.,_,._,._ 2
11、5 8.5 PROP format for parallel HDDR (Pseudo random odd parity) 26 8.5.1 General ._._._._._.,_._ 26 . . . III ISOllEC 8441-2:1991 (E) 8.52 Summary of PROP format . . . . . . . _._._._,_,_. 85.3 PROP format bandwidth utilization .,.,.,.,.,_._._,_ B.6 3PM formats for parallel HDDR . . . . . . . . . . .
12、 . . . . . . . . . . . _ B.6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _._._. B.6.2 3PM format versions . . . . . . . . . . . . . . . . . . . . . . . . . . . _._._ 8.6.3 Error detection and correction (formats A and B) _,., 8.6.4 Summary of 3
13、PM formats A and B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ 8.6.5 3PM format bandwidth utilization . . . _._._._._. B.7 MODAS airborne recording format ._._.,._,.,._.,._,._. 8.7.1 General . . . . . . . . . . . . . . . 8.7.2 Description . . . . . . . . . . . . . . . . . . . .
14、 . . . . . . . . . . . . . . . . . . . . . _. 27 27 27 27 28 29 29 30 30 30 30 ISOllEC 8441-2:1991(E) Foreword IS0 (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized systern for worldwide standardization. National bodies
15、that are members of IS0 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. IS0 and IEC technical com- mittees collaborate in fields of mutual interest. Other in
16、ternational or- ganizations, governmental and non-governmental, in liaison with IS0 and IEC, also take part in the work. In the field of information technology, IS0 and IEC have established a joint technical committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical commi
17、ttee are circulated to national bod- ies for voting. Publication as an International Standard requires ap- proval by at least 75 % of the national bodies casting a vote. International Standard ISO/IEC 8441-2 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology. ISO/IEC 844
18、1 consists of the following parts, under the general title In- formation technology - High density digital recording (HDDR): - Part 1: Unrecorded magnetic tape for (HDDR) applications - Part 2: Guide for interchange practice Annexes A and B of this part of ISO/IEC 8441 are for information only V INT
19、ERNATIONAL STANDARD ISOllEC 8441-2:1991(E) Information technology - High density digital recording (HDDR) - Part 2: Guide for interchange practice 1 Scope This part of ISO/IEC 8441 specifies the minimum performance levels necessary for the effective interchange of information using High Density Digi
20、tal Recording (HDDR). It also describes methods of testing for determining these levels. It gives guid- ance on recorders/reproducer characteristics, modes of recording, and modulation patterns. The imperial dimensions given in this part of ISO/IEC 8441 are the reference dimensions. The metric and i
21、mperial dimensions are, however, given to a sufficient degree of accuracy as to be totally interchangeable. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO/IEC 8441. At the time of publica- tion, the e
22、ditions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO/IEC 8441 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and IS0 maintain registers of cur- ren
23、tly valid International Standards. ISO/IEC 3788:1990, Information processing - g-track, 12,7 mm (0,5 in) wide magnetic tape for information interchange using phase encoding at 126 ftpmm (3 200 ftpi), 63 cpmm (1 600 cpi). IS0 6068:1985, Information processing - RecordirJg characteristics of instrumen
24、tation nJagnetic tape (i/J- CllldilJg telemetry systems) - Interchange require- ments. ISO/IEC TR 6371:1989, Information processing - InfetChalJge practices and test methods for unre- corded instrumentation magnetic tape. 3 Definitions For the purposes of this part of ISO/IEC 8441, the following def
25、initions apply. 3.1 aliasing: The false lower frequency components resulting from an insufficient sampling rate (i.e. less than required by the sampling theorem) when re- constructing an analogue signal from its sampled data representation. 3.2 baseline restorer: A device to restore the d.c. compone
26、nt removed by the record/reproduce pro- cess. 3.3 bit error: The incorrect interpretation of a bi- nary bit by a message processing unit. 3.4 bit error rate (BER): The rate at which bit errors occur in a message processing unit, expressed in terms of the number of bit errors divided by the total num
27、ber of bits processed in a given period of time, or from a given length of tape. 3.5 bit packing density: The number of bits re- corded per unit track length, usually expressed in terms of bits per millimetre (bit/mm) or kilobits per inch (kbit/in). 3.6 bit slip: The condition in a message processin
28、g unit where the bit rate clock has gained (or lost) more than 180” phasing with respect to synchronism with the binary message bits. ISOllEC 8441-2:1991(E) 3.7 bit synchronizer: An information processing unit intended to extract the binary message and as- sociated bit rate clock included in a pulse
29、 code modulation (PCM) signal. 3.8 cross play: The ability to record and reproduce on the same or a different machine, or record at one speed and reproduce at the same or different speed. 3.9 cross talk: Interference signals that are coupled from adjacent channels into a given processing unit channe
30、l, usually expressed in terms of decibels down from full scale amplitude of the unit channel. 3.10 data azimuth: The instantaneous angle in the plane of the tape between a line perpendicular to the reference edge and either of the two parallel lines defining data scatter. NOTE 1 Data azimuth may be
31、expressed as the sum of static and dynamic components in the form A + BAt) where s I fit)dt = 0 0 3.11 data azimuth (dynamic): The maximum angu- lar deviation, over a period of time, of the data azimuth from its mean value as defined by data azimuth (static). For the purpose of this definition, the
32、word “maximum” is interpreted as being at the 95 % probability level. For a Gaussian distribution, this is two standard deviations (20). NOTE 2 Data azimuth (dynamic) is the maximum value of the quantity Rs(/) in 3.10. 3.12 data azimuth (static): The mean value, over a period of time, of the data az
33、imuth. NOTE 3 Data azimuth (static) is the quantity R in 3.10. 3.13 data scatter: The minimum distance between two parallel lines, in the plane of the tape, enclosing all data transitions recorded simultaneously on all tracks in t.he same head. NOTE 4 The errors in location and angular relation amon
34、g transient data recorded simultaneously on all odd or even tracks are defined by the terms: data azimuth, data scatter, and individual track data azimuth difference. These are approximately equivalent to the terms: head azimuth, gap scatter, and head segment gap azimuth dif- ference; however, guidi
35、ng misalignment is included in the data location error definition. 3.14 data spacing: The distance on the tape be- tween simultaneous events recorded on odd and even numbered tracks when interlaced heads are used. NOTE 5 When recording, this is equal to the head spacing, but on reproducing it is equ
36、al to head spacing only when the record and reproduce tensions and head spacing are equal. 3.15 decoder: Information recovery device that ac- cepts digital signals from the tape reproducer and converts them into a form suitable for the output interface. 3.16 digital recording code: The on-tape digit
37、al coding of the recorded binary message. 3.17 dropout: Reduction in the reproduce signal amplitude severe enough to cause bit errors. 3.18 duty factor (of a pulse): The ratio of pulse du- ration to pulse period, often expressed as a per- centage. 3.19 edge margin (A!): The distance between the outs
38、ide edge of the highest numbered track and the tape edge (see figure 3). 3.20 edge margin, minimum (A!,): The minimum value of the edge margin. NOTE 6 This value places an additional constraint on track configurations since, in general, the simultaneous application of all worst-case tolerances for t
39、rack width, track location, and tape width will result in a value of edge margin less than A,. 3.21 encoder: A processing device that accepts a data stream at its input and converts it to appropri- ate digital signals to be recorded on tape. 3.22 error detection: The process of detecting bit errors.
40、 3.23 error correction: The process of correcting detected bit errors. 3.24 eye pattern: The pattern as displayed on an oscilloscope, that results from the superpositioning of the waveforms of the different symbols in a digital data sequence. It is used for assessing the quality of the replayed digi
41、tal signal. 3.25 flaw: An imperfection in the tape oxide coating due to oxide or slitting debris, foreign particulate matter, absence of coating, etc. NOTE 7 Such imperfections are the major source of dropouts. Other imperfections such as failure to maintain slitting tolerances and other physical no
42、nuniformities can cause poor tracking which results in reproduce signal fluctuations similar to dropouts. 3.26 flutter: Tape speed errors at frequencies above 0.5 Hz. 2 ISOllEC 8441-2:1991(E) 3.27 flux transition: A 180” change in the flux pat- tern in a magnetic medium, brought about by the reversa
43、l of the magnetic poles within the medium. 3.28 flux transition density: The number of flux transitions (i.e. flux reversals) per unit track length. 3.29 frame synchronizer: A processing device to detect and synchronize frames and subframes of a pulse code modulation bit stream. 3.30 gap length: Dis
44、tance from the leading edge to the trailing edge of head gap measured perpen- dicular to the track width (see figure 1). 3.31 gap scatter: The minimum distance between two parallel lines, in the plane of the tape, between which all the gap trailing edges of a record head are embraced (see figure 1).
45、 3.32 head: A group of individual head segments in a fixed assembly. 3.33 head azimuth: The angle formed in the plane of the tape, between a line passing through the gap centres of the two outside head segments and a line perpendicular to the head reference plane (see fig- ure 1). 3.34 head 1: The f
46、irst record or reproduce head over which an element of tape passes when moving in the normal operating direction (see also 3.39). 3.35 head reference plane: A plane, which may be imaginary, that is parallel to the reference edge of the tape and perpendicular to the-plane of the tape. NOTE 8 For the
47、purpose of this definition the tape is considered as perfect (see figure 1). 3.36 head segment: A single transducer that re- cords or reproduces one track (see figure 1). 3.37 head segment gap azimuth: The angle, formed in the plane of the tape, between a line perpendicu- lar to the head reference p
48、lane and a line parallel to the trailing edge of the gap in a record head seg- ment (see figure 1). 3.38 head segment gap azimuth difference: The angular deviation of the azimuth of a head segment gap from the head azimuth. 3.39 head segment number: The number of the head segment corresponding to the track number on the magnetic tape on which that head segment normally operates (see figure 2). NOTE 9 Head 1 of a pair contains all odd-numbered segments, while head 2 contains all even-numbered seg- ments (see figure 1 and figure 2). 3.40 head spacing (S): The distance along the tape pat
