1、I ANSIINCITS 261-1996 (R2001) (formerly ANSI X3.261-1996 (R2001) for Information Technology - Extended Magnetic Tape Format for Information Interchange (3 6- Track, Parallel Serpentine, 12.65 mm (0.50 in), 1491 cpmm (37871 cpi), Group- Coded Recording) Developed by Where IT all begins ANSI X3.261-19
2、96 American National Standard for Information Technology - Extended Magnetic Tape Format for Information Interchange (36-Track, Parallel Serpentine, 12.65 mm (0.50 in), 1491 cpmm (37 871 cpi), G roup-Coded Recording) Secretariat Information Technology Industry Council Approved April 8, 1996 American
3、 National Standards Institute, Inc. Approval of an American National Standard requires review by ANSI that the requirements for due process, consensus, and other criteria for approval have been met by the standards developer. Consensus is established when, in the judgment of the ANSI Board of Standa
4、rds Review, substantial agreement has been reached by directly and materially affected interests. Substantial agreement means much more than a simple majority, but not necessarily unanimity. Consensus requires that all views and objections be considered, and that a concerted effort be made toward th
5、eir resolution. The use of American National Standards is completely voluntary; their existence does not in any respect preclude anyone, whether he has approved the standards or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not conforming to the standard
6、s. The American National Standards Institute does not develop standards and will in no circumstances give an interpretation of any American National Standard. Moreover, no person shall have the right or authority to issue an interpretation of an American National Standard in the name of the American
7、 National Standards Institute. Requests for interpretations should be addressed to the secretariat or sponsor whose name appears on the title page of this standard. CAUTION NOTICE: This American National Standard may be revised or withdrawn at any time. The procedures of the American National Standa
8、rds Institute require that action be taken periodically to reaffirm, revise, or withdraw this standard. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Standards Institute. American National Published by American
9、National Standards Institute 11 West 42nd Street, New York, New York 10036 Copyright O1 996 by Information Technology Industry Council (ITI) All rights reserved. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without prior written permissio
10、n of ITI, 1250 Eye Street NW, Washington, DC 20005. Printed in the United States of America Contents Foreword . . Page II 1 2 3 4 5 6 7 8 9 10 11 12 Scope. purpose. and application . 1 Normative references . 2 Definitions 2 Tape characteristics . 4 Recording 5 Track format . 8 Tape format 10 Packet
11、format . 18 Data block format . 21 Recorded-block format 25 Error-correction code (ECC) . 28 Recording of bytes on tape . 29 Tables 1 Track identification . 9 2 Recording area . 10 3 Mark and gap codes . 16 Figures 1 2 3 4 5 6 7 8 9 10 11 Usable recording area 10 Density identification mark 11 Order
12、 of wrap marks . 15 Shift register representation 17 Packet 18 Data portion of the data block . 21 Data block frame format 24 Recorded-block format 25 Summary of frames . 27 Error correcting code 28 8/9 group-code conversion 30 Annex A Measurement of bit shift . 32 I Foreword (This foreword is not p
13、art of American National Standard X3.261-1996.) This standard presents format and recording requirements for 12.65 mrn (0.50 in) 36-track magnetic tape to be used for information interchange among processing systems, communication systems, and associated equipment. This standard deals solely with re
14、cording on magnetic tape. The X3B5 Subcommittee on Digital Magnetic Tape, which developed this standard, consists of experienced and qualified specialists in manufactur- ing magnetic tape, and in recording digital information on magnetic tape. This standard is the third to utilize this cartridge for
15、m factor and the first to use the enhanced capacity tape. The recording format represents a signifi- cant advancement in reliability and volumetric efficiency for 12.65-mm (0.50-in) magnetic tape. In the development of this standard, careful con- sideration was given to current practices, existing e
16、quipment and supplies, and the broadest possible acceptance, and to providing a basis for future improvements in the use of the cartridge medium. The standard contains specifications for a recording format. The text of this standard differs from the corresponding IS0 and ECMA standards ISO-14251 and
17、 ECMA-196; however, it is the intent of this standard to be technically the same. There is one annex in this standard. Annex A is normative and is consid- ered part of this standard. Suggestions for improvement of this standard will be welcome. They should be sent to Information Technology Industry
18、Council, 1250 Eye Street, NW, Suite 200, Washington, DC 20005. This standard was processed and approved for submittal to ANSI by Accredited Standards Committee on Information Technology, X3. Committee approval of the standard does not necessarily imply that all members voted for its approval. At the
19、 time it approved this standard, the X3 Committee had the following members: James D. Converse, Chair Donald C. Loughry, Vice-Chair Kate McMillan, Secretary Organiza tion Represented Name of Representative American Nuclear Society Geraldine C. Main Sally Hartzell (Alt.) AMP, Inc. Edward Kelly Charle
20、s Brill (Alt.) Apple Computer, Inc. . David K. Michael Jerry Kellenbenz (Alt.) AT -A O is represented by a transition at the beginning of the bit-cell followed by a transition at the center of the bit-cell. 5.1 Physical recording density The physical recording density shall be: - For all Os: - For a
21、ll 7s: 1944 ftpmm (49 378 ftpi) 972 ftpmm (24 689 ftpi) 52 Bit-cell length The resulting nominal bit-cell length is 1 .O288 pm (40.504 pin). 53 Average bit-cell length The average bit-cell length is the sum of distances over n bit-cells divided by n. 53.1 Long-term average bit-cell length The long-t
22、erm average bit-cell length shall be the average bit-cell length taken over a minimum of 972 O00 bit-cells. It shall be within f4 percent of the nominal bit-cell length. 532 Short-term average bit-cell The short-term average bit-cell length (STA) shall be the average taken over 16 bit-cells. It shal
23、l be within f7 percent of the nominal bit-cell length. 5.4 Bit rate of change Bit rate of change shall meet both of the following requirements. These requirements shall be met throughout the length of the tape. 5 ANSI X3.261-1996 STA, 64 bits 5.4.1 Bit-cell peak position The maximum bit-cell peak po
24、sition variation shall be 30% of its expected value when measured as follows: ST*,+, A 64 bits4 a) Write a continuous all 7s pattern in the areas to be measured; b) Measure over a rolling 64-bit global window, eliminating any samples that contain missing pulses. The sample shall be preceeded and suc
25、ceeded by 5 7 bits to eliminate intersymbol interference from the measurement; c) Find the average bit-cell peak position within the 64 bit-cell window by determining the total distance between the end bit-cell peaks and dividing by 63. Any bit-cell peak shall be within the specified tolerance of it
26、s expected position within that 64 bit-cell window. The adjacent 64-bit windows, containing random data patterns, shall not contain any missing pulses. 55 Bit shift The maximum displacement of any 7s zero crossing, exclusive of dropouts, shall not deviate by more than 28 percent from the expected no
27、minal position as defined by the average bit-cell length. See Annex A for the test procedure. 56 Total character skew No bit belonging to the same written transversal column shall be displaced by more than 19 bit-cell lengths when measured in a direction parallel to the tape-reference edge. 5.7 Read
28、 signal amplitude The average peak-to-peak signal amplitude of an interchanged cartridge averaged over 4000 flux transitions at 972 ftpmm (24 689 ftpi) shall be between 60% and 150% of the standard reference amplitude. Averaging for the interchange cartridge may be segmented into blocks. Traceabilit
29、y to the standard reference amplitude is provided by the calibration factors supplied with each secondary standard reference tape. 5.8 Missing pulse zones A missing pulse zone begins with a missing pulse and ends when 64 consecutive flux transitions with no missing pulses are detected or a length of
30、 1 mm of tape has been measured. 6 ANSI X3.261-1996 5.9 Coincident missing pulse zones For purposes of measuring coincident missing pulse zones, the 36 tracks on the tape are divided into four 9-track groups as shown below. A simultaneous missing pulse zone condition on two or more tracks of a 9-tra
31、ck group is a coincident missing pulse zone. The first group shall comprise physical tracks 1, 5, 9, 13, 17, 21, 25, 29, and 33. The second group shall comprise physical tracks 3,7,11, 15,19,23,27,31, and 35. The third group shall comprise physical tracks 2, 6, 10, 14, 18, 22, 26, 30, and 34. The fo
32、urth group shall comprise physical tracks 4, 8, 12, 16, 20, 24, 28, 32, and 36. If a coincident missing pulse zone occurs at the same time in the first and second group of tracks or the third and fourth group of tracks, it shall be considered as a single coincident missing pulse zone. Its length sha
33、ll begin with the start of the earliest coincident missing pulse zone and terminate with the end of the latest coincident missing pulse zone. No coincident missing pulse zones shall be permitted in a recorded block. No coincident missing pulse zones shall exceed 50 mm (1.97 in). 7 ANSI X3.261-1996 6
34、 Track format 6.1 Number of tracks There shall be 36 tracks organized in 2 interleaved half wraps of 18 tracks each. 62 Track positions The distance from the centerline of the tracks to the tape reference edge shall be: Track 1 Track 2 Track 3 Track 4 Track 5 Track 6 Track 7 Track 8 Track 9 Track 1
35、O Track 11 Track 12 Track 13 Track 14 Track 15 Track 16 Track 17 Track 18 Track 19 Track 20 Track 21 Track 22 Track 23 Track 24 Track 25 Track 26 Track 27 Track 28 Track 29 Track 30 Track 31 Track 32 Track 33 Track 34 Track 35 Track 36 11.838 rnrn (0.46606 in) 11.523 rnrn(0.45366 in) 11.208 rnm (0.4
36、4126 in) 10.893 rnrn (0.42886 in) 10.578 rnrn (0.41646 in) 10.263 rnrn (0.40406 in) 9.948 mrn (0.39165 in) 9.633 mm (0.37925 in) 9.31 8 rnrn (0.36685 in) 9.003 rnrn (0.35445 in) 8.688 rnrn (0.34205 in) 8.373 rnrn (0.32965 in) 8.058 rnm (0.31 724 in) 7.743 rnm (0.30484 in) 7.428 rnrn (0.29244 in) 7.1
37、 13 rnrn (0.28004 in) 6.798 rnrn (0.26764 in) 6.483 rnrn (0.25524 in) 6.168 rnm (0.24283 in) 5.853 mrn (0.23043 in) 5.538 rnrn (0.21803 in) 5.223 rnrn (0.20563 in) 4.908 rnrn (0.1 9323 in) 4.593 rnrn (0.1 8083 in) 4.278 mrn (0.16843 in) 3.963 rnm (0.15602 in) 3.648 rnrn (0.14362 in) 3.333 rnrn (0.13
38、122 in) 3.01 8 rnrn (0.1 1882 in) 2.703 rnm (0.10642 in) 2.388 rnrn (0.09402 in) 2.073 rnrn (0.08161 in) 1.758 rnrn (0.06921 in) 1.443 mrn (0.05681 in) 1.128 rnrn (0.04441 in) 0.81 3 rnrn (0.03201 in) The tolerance shall be f0.040 rnrn (f0.00159 in) for all tracks. 63 Track width The width of the wr
39、itten track shall be 0.285 rnrn f0.012 rnm (0.01 122 in f0.00047 in). 8 ANSI X3.261-1996 6.4 Azimuth The azimuth shall be less than 3 minutes of arc. NOTE - At the time of tape writing, the azimuth should be less than 2.5 minutes of arc. The remaining 0.5 minutes of arc are the allowance for tape di
40、stortion caused by environmental conditions and aging. 65 Track identification The 36 physical tracks are allocated to 2 sets of 18 tracks each, called half wrap 1 and half wrap 2. The physical tracks with an odd physical track number shall constitute half wrap 1; those with an even physical track n
41、umber shall constitute half wrap 2. (See table 1 .) Table 1 -Track identification Physical Track 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 k Track 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 If Wrap 1 Byte data byte 1 data byte 8 data byte 2
42、data byte 9 data byte 3 data byte 10 data byte 4 data byte 11 data byte 5 data byte 12 data byte 6 data byte 13 data byte 7 data byte 14 ecc byte 2 ecc byte 3 ecc byte 1 ecc byte 4 H; Track 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 data byte 1 date byte 8 data byte 2 data byte 9 data byte 3 data
43、byte 10 data byte 4 data byte 11 data byte 5 data byte 12 data byte 6 data byte 13 data byte 7 data byte 14 ecc byte 2 ecc byte 3 ecc byte 1 ecc byte 4 9 ANSI X3.261-1996 7 Tapeformat 7.1 Recording area The recording area, for both half wraps, shall be bounded by BOT and EOT, as shown in figure 1. L
44、BAP is the leader block attachment point. EOT shall be greater than 4.3 m (169 in) from the tape to hub junction. (See table 2.) Leader block Density ID and volid mark area / BOT EOV J J I Tape back 23 t Tape reference edge EOT .) -_ _ T Recording surface Track 1 Track 36 Tape to hub junction Figure
45、 1 - Usable recording area Table 2 - Recording area The recorded area of tape between BOT and EOT shall be partitioned by the following marks and gaps: - density-identification mark; - ID-separator mark; - interblock gap; - erase gap; -tape mark; - wrap mark; - VOLID mark. 10 ANSI X3.261-1996 Densit
46、y ID mark The marks and gaps are defined by all-7s or tone patterns written in groupings of tracks called zones. Tone shall be written on tape as the repeated 6-bit pattern 100000,. half wrap 1 data ID IBG sep 72 Zones The 18 tracks within each half wrap shall be divided into six distinct zones: hal
47、f wrap tracks Zone A: 1, 7, 13 Zone B: 2, 8, 14 ZoneC: 3, 9, 15 Zone D: 4, 10, 16 Zone E: 5, 11, 17 Zone F: 6, 12, 18 All ZEROS 73 Density-identification mark The density-identification mark shall be characterized by: In half wrap 1: -all 1s in zones B, C, E -tone in zones A, D, F - An all Os patter
48、n shall be written towards BOT. In half wrap 2: The density-identification mark (figure 2) shall be written in one of two modes. Mode one shall be used when no VOLID mark is to be written. Mode two shall be used when a VOLID mark is to be written. Use of the VOLID mark is optional. half wrap 2 data
49、ID . sep IBG Density ID mark VOLID half wrap 1 mark data I I LBAP BOT All ZEROS I EOV half wrap 2 data EOV Figure 2 - Density identification mark ANSI X3.261-1996 The length of the density-identification mark in half wrap 1 on a CST tape, when no VOLID mark is written, shall be: nominal: 2375 mm (94 in) minimum: 2250 mm (89 in) maximum: 3060 mm (120 in) The length of the density-identification mark in half wrap 1 on a CST tape, when a VOLID mark is written, shall be: nominal: 21 95 mm (86 in) minimum: 2070 mm (81 in) maximum: 2880 mm (1 13 in) The area that is written with an all Os
