1、ANSI INCITS 181-1990 (R2001) (formerly ANSI X3.181-1990 (R2001)for Information Systems Recorded Magnetic Tape and Cartridgefor Information Interchange 112 inch (12.65 mm), Serial Serpentine,22-Track, 6 667 bpi (262 bpmm),and 48-Track, 10 000 bpi (394 bpmm),MFM-Encoded Requirements for RecordingANSI
2、X3.1 81-1990 American National Standard for Information Systems - Recorded Magnetic Tape and Cartridge for Information Interchange - l/2 inch (12.65 mm), Serial Serpentine, 22-Track, 6 667 bpi (262 bpmm), and 48-Track, IO 000 bpi (394 bpmm), MFM-Encoded - Requirements for Recording Secretariat Compu
3、ter and Business Equipment Manufacturers Association Approved January 16,199O American National Standards Institute, Inc AmericanNationalStandardApproval of an American National Standard requires review by ANSI that therequirements for due process, consensus, and other criteria for approval havebeen
4、 met by the standards developer.Consensus is established when, in the judgment of the ANSI Board of StandardsReview, substantial agreement has been reached by directly and materiallyaffected interests. Substantial agreement means much more than a simplemajority, but not necessarily unanimity. Consen
5、sus requires that all views andobjections be considered, and that a concerted effort be made toward theirresolution.The use of American National Standards is completely voluntary; their existencedoes not in any respect preclude anyone, whether he has approved the standardsor not, from manufacturing,
6、 marketing, purchasing, or using products, processes,or procedures not conforming to the standards.The American National Standards Institute does not develop standards and will inno circumstances give an interpretation of any American National Standard.Moreover, no person shall have the right or aut
7、hority to issue an interpretation ofan American National Standard in the name of the American National StandardsInstitute. Requests for interpretations should be addressed to the secretariat orsponsor whose name appears on the title page of this standard.CAUTION NOTICE: This American National Standa
8、rd may be revised orwithdrawn at any time. The procedures of the American National StandardsInstitute require that action be taken periodically to reaffirm, revise, or withdrawthis standard. Purchasers of American National Standards may receive currentinformation on all standards by calling or writi
9、ng the American National StandardsInstitute.Published byAmerican National Standards Institute11 West 42nd Street, New York, New York 10036Copyright 1990 by Information Technology Industry Council (ITI)All rights reserved.No part of this publication may be reproduced in anyform, in an electronic retr
10、ieval system or otherwise,without prior written permission of ITI, 1250 Eye Street NW,Washington, DC 20005.Printed in the United States of AmericaForeword (This Foreword is not part of American National Standard X3.181-1990.) This standard presents format and recording requirements for l/2 inch (12.
11、65 mm), 22- or 48-track magnetic tape, to be used for information interchange among processing systems, communication systems, and associated equipment utilizing a standard code for interchange. This standard deals solely with recording on magnetic tape. The X3B.5 Subcommittee on Magnetic Tape, whic
12、h developed this standard, consists of experienced and qualified specialists in recording digital information on magnetic tape. In the development of this standard, careful consideration was given to current practices, existing equipment and supplies, and the broadest possible acceptance, and to pro
13、viding a basis for future improvements in the use of this cartridge medium. Requests for interpretation, suggestions for improvement or addenda, or defect reports are welcome. They should be sent to the X3 Secretariat, Computer and Business Equip- ment Manufacturers Association, 3 11 First Street, N
14、W, Suite 500, Washington, DC 20001-2178. This standard was processed and approved for submittal to ANSI by American National Standards Committee on Information Processing Systems, X3. Committee approval of the standard does not necessarily imply that all committee members voted for its ap- proval. A
15、t the time it approved this standard, the X3 committee had the following members: Richard Gibson, Chair Donald C. Loughry, Vice-Chair Jean-Paul Emard, Administrative Secretary Organization Represented Name of Representative Allen-Bradley Company . Ronald H. Reimer American Library Association Paul P
16、eters American Nuclear Society Geraldine C. Main AMP, Inc Sally Hartzell (Ah) . Edward Kelly Apple Computer, Inc Ronald Lloyd (Alt) . Karen Higginbottom Michael J. Lawler (Alt) Apple Professional Users Group . Ira Wilson Association of the Institute for Certification of Computer Professionals Kennet
17、h Zemrowski Eugene M. Dwyer (Alt) AT or +2 percent, - 2.6 percent, for low density. As shown in Figure 2, the time between adjacent peaks in the 11 interval is denoted as Tl. The time between the last 1 in the 11 interval and the last 1 in the following 11 interval is denoted as To. Peak Shift = 3T,
18、-T, l 100 4.4 Read Signal Amplitude. The signal amplitude shall be measured at a point in the read channel where the signal is proportional to the rate of change of flux in the read head. The average signal amplitude of an interchanged cartridge averaged over a minimum of 1.0 inch (25.4 mm) at the r
19、ecording density, shall be between 75 percent and 125 percent of the standard reference amplitude. Averaging for the interchange cartridge may be segmented into blocks. No dropouts are allowed within the measured area. Traceability to the standard reference amplitude is provided by the calibration f
20、actors supplied with each secondary reference tape. 4.5 Overwrite. For the two recording modes, the overwrite ratio for the tape shall be less than 120 percent of the same ratio for the master standard reference tape. Traceability to the overwrite ratios of the master standard reference tape is prov
21、ided by calibration factors supplied with each secondary standard reference tape. 4.6 Azimuth. The angular deviation of the recorded flux transitions from a line normal to the reference edge of the tape shall be less than 15 minutes (4.3 milliradians) of arc. 5. Format of Track 5.1 Reference Edge of
22、 Tape. The reference edge of the tape is the top edge when viewing the recording side of the tape with the hub end (EOT) of the tape to the observers right. 5.2 Calibration Tracks. Calibration tracks are used to establish track position reference values and initial read-back gain values for specific
23、 media/head combi- nations. Calibration tracks are not prerecorded on the tape. The drive mechanism that records data on a cartridge for the first time shall write the calibration tracks as described in the following subparagraphs. Refer to Figure 3. 5.2.1 Calibration Track A. Calibration Track A sh
24、all be recorded on tapes recorded in either the low density or high density mode. The distance of the centerline of Calibration Track A from the top edge of the tape shall be 0.143 inch f 0.001 inch (3.63 mm + 0.03 mm). Calibration Track A shall be recorded with contigu- ous repetitions of bit combi
25、nations (b, to b,) 01 recording in the direction towards the EOT marker. Calibration Track A shall begin: 30 inches (762 mm) + 4 inches (102 mm) from the BOT marker Calibration Track A shall end: 119 inches (3023 mm) + 3 inches (76 mm) from the BOT marker 5.2.2 Calibration Track B. Calibration Track
26、 B shall be recorded only on tapes recorded in high- density mode. Calibration Track B shall be located 0.027 inch + 0.001 inch (0.686 mm + 0.03 mm) below Calibration Track A. Calibration Track B shall be recorded with contigu- ous repetitions of bit combinations (b, to b,) 01 recording in the direc
27、tion towards the EOT marker. Calibration Track B shall begin: 30 inches (762 mm) + 4 inches (102 mm) from the BOT marker Calibration Track B shall end: 119 inches (3023 mm) f 3 inches (76 mm) from the BOT marker 5.2.3 Calibration Track C. Calibration Track C shall be recorded only on tapes recorded
28、in low-density mode. Calibration Track C shall be located 0.214 inch f 0.001 inch (5.44 mm Ifr 0.03 mm) below Calibration Track A. 11 AMEWCANNATIONALSTANDARDX3.181-1990 Calibration Track C shallbe recorded with contigu- ous repetitions of bit combinations (b, to b,J 01 recording in the direction tow
29、ards the BOT marker. Calibration Track C shall begin: 106 inches (2692 mm) f 3 inches (76 mm) from the BOT marker Calibration Track C shall end: 30 inches (762 mm) + 4 inches (102 mm) from the BOT marker 5.2.4 Calibration Track D. Calibration Track D shall be recorded only on tapes recorded in high-
30、 density mode. Calibration Track D shall be located 0.214 inch Itr 0.001 inch (5.44 mm f 0.03 mm) below Calibration Track B. Calibration Track D shall be recorded with contigu- ous repetitions of bit combinations (b, to b,) 01 recording in the direction towards the BOT marker. Calibration Track D sh
31、all begin: 106 inches (2692 mm) f 3 inches (76 mm) from the BOT marker Calibration Track D shall end: 30 inches (762 mm) + 4 inches (102 mm) from the BOT marker 5.3 Positions of Track 53.1 Identification of Track 5.3.1.1 Forward Tracks. Tracks recorded in the forward direction (from BOT to EOT) are
32、num- bered with even integer values beginning with 0. These tracks are referenced to Calibration Track A and Calibration Track B (high density only). Refer to Figure 4. 5.3.1.2 Reverse Tracks. Tracks recorded in the reverse direction (from EOT to BOT) are numbered with odd integer values beginning w
33、ith 1. These tracks are referenced to Calibration Track C (low density) and Calibration Track D (high density). Refer to Figure 4. 5.3.2 References of Track Base. Data track centerline locations shall be referenced to the center- line of the respective calibration tracks at an accuracy off 0.0005 in
34、ch (k 0.013 mm). Offset dimensions with a negative value indicate that the data track is located below the referenced calibration track. 5.3.3 Number of Tracks low density: 22 tracks numbered 0 to 21, inclusive. high density: 48 tracks numbered 0 to 47, inclusive. Refer to Figure 4. 12 5.4 Spacing o
35、f Track. The spacing between recorded tracks shall be: low density: 0.0190 inch f 0.0005 inch (0.483 mm + 0.013 mm) high density: 0.0090 inch + 0.0005 inch (0.229 mm f 0.013 mm) Refer to Figure 4. 5.5 Width of Track. The width of the recorded track shall be: low density: 0.0180 inch + 0.0005 inch (0
36、.457 mm * 0.013 mm) high density: 0.0085 inch f 0.0005 inch (0.216 mm + 0.013 mm) 6. Format of Tape The recorded area of tape between BOT and EOT shall be partitioned by the following areas (refer to Figure 5): (1) Calibration areas (2) Guard areas (3) Synchronization areas (4) Dataareas 6.1 Recordi
37、ng Area. The recording area shall be bounded by BOT and EOT. The total length of the recording area shall be at least 625 feet-t 5 feet (190.5 meters f 1.5 meters). Recording of the data tracks takes place in two directions: Forward (BOT to EOT) and reverse (EOT to BOT). 6.2 Calibration Areas. The l
38、ocation and contents of the calibration areas are described in 5.2. 6.3 Forward Guard Areas. Forward guard areas shall not be used to record any data or synchronization pattern. In the forward direction (BOT to EOT), the guard areas shall begin at the end of the calibration area and shall end: Nomin
39、al: 143 inches (3632 mm) from the BOT marker, Minimum: 143 inches (3632 mm) from the BOT marker, Maximum: 155 inches (3937 mm) from the BOT marker. 6.4 Forward Synchronization Areas. In the forward direction (BOT to EOT), the forward synchronization areas shall be provided for the purpose of allowin
40、g the data recovery circuits to prepare for the subsequent data areas. In the low-density mode, a contiguous repetition of bit combination (b, to b,) 01 may be optionally AMERICAN NATIONAL STANDARD X3.181-1990 recorded immediately before the forward data areas. In the high-density mode, these synchr
41、onization areas must be left in a dc-erased state. The forward synchronization areas shall begin at the end of the forward guard areas and shall extend: Nominal: 12 inches (305 mm), Minimum: 12 inches (305 mm), Maximum: 48 inches (1219 mm). 6.5 Forward Data Areas. In the forward direction (BOT to EO
42、T), the data areas shall immediately follow the forward synchronization areas and shall end: Nominal: 611.6 feet (186.4 meters) from the BOT marker, Minimum: 601.6 feet (183.4 meters) from the BOT marker, Maximum: 613.6 feet (187.0 meters) from the BOT marker. 6.6 Reverse Synchronization Areas. In t
43、he reverse direction (EOT to BOT), the reverse synchronization areas shall be provided for the purpose of allowing the data recovery circuits to prepare for the subsequent data areas. In the low-density mode, a contiguous repetition of bit combination (b, to b,) 01 may be optionally recorded immedia
44、tely before the reverse data areas. In the high-density mode, these synchronization areas must be left in a dc-erased state. The reference point is the end of the forward data areas. The reverse synchronization areas shall begin: Nominal: 12 inches (305 mm) beyond the reverse reference point, Minimu
45、m: 00 inches (00 mm) beyond the reverse reference point, Maximum: 12 inches (305 mm) beyond the reverse reference point. The reverse synchronization areas shall end: Nominal: 12 inches (305 mm) before the reverse reference point, Minimum: 12 inches (305 mm) before the reverse reference point, Maximu
46、m: 48 inches (1219 mm) before the reverse reference point. 6.7 Reverse Data Areas. In the reverse direction (JOT to BOT), the data areas shall immediately follow the reverse synchronization areas and shall end: Nominal: 156 inches (3962 mm) from the BOT marker, Minimum: 276 inches (7010 mm) from the
47、 BOT marker, Maximum: 132 inches (3353 mm) from the BOT marker. 6.8 Reverse Guard Areas. Reverse guard areas shall not be used to record any data or synchronization pattern. The guard areas shall begin at the end of the reverse recorded data area and shall end at the beginning of the calibration C/D
48、 area. 7. Format of Data 7.1 General. Prior to recording, the data bytes shall be arranged in groups, called blocks. These blocks are arranged in larger groups, called entities, which are complete with computed error-correcting-code (ECC) blocks. The data so arranged shall then be recorded on tape.
49、7.2 Data Bytes. T-he data bytes consist of: (1) User bytes (2) Pad bytes 7.2.1 User Bytes. User bytes are 8-bit bytes at the disposal of the user of the tape cartridge for the recording of information to be interchanged or stored. Bach of the bits b, - b, can be either a ZERO or a ONE when the representation is coded in accordance with a standard that permits such encoding, as agreed upon by the interchange parties. Binary weight 27 26 25 24 23 22 2 2O Bit designation b, b7 b, b5 b4 b, b* bl Bit position in byte 8 7654321 7.2.2 Pad Bytes. Pad bytes are 8-bit bytes that have a bit
