ANSI INCITS 158-1987 Information Systems - Recorded Magnetic Tape Cassette for Information Interchange - 4 Track 0.150 inch (3.81 mm) 8000 bpi (315 bpmm) Group Code Recording.pdf

1、ANSI INCITS 158-1987 (R2003)(formerly ANSI X3.158-1987 (R1998)for Information Systems Recorded Magnetic Tape Cassettefor Information Interchange 4 Track, 0.150 Inch (3.81 mm),8000 bpi (315 bpmm),Group Code RecordingAmericanNationalStandardApproval of an American National Standard requires review by

2、ANSI that therequirements for due process, consensus, and other criteria for approval havebeen 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. Subs

3、tantial agreement means much more than a simplemajority, but not necessarily unanimity. Consensus 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

4、 any respect preclude anyone, whether he has approved the standardsor not, from manufacturing, 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 in

5、terpretation of any American National Standard.Moreover, no person shall have the right or authority 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

6、 name appears on the title page of this standard.CAUTION NOTICE: This American National Standard 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 A

7、merican National Standards may receive currentinformation on all standards by calling or writing the American National StandardsInstitute.Published byAmerican National Standards Institute11 West 42nd Street, New York, New York 10036Copyright 1987 by Information Technology Industry Council (ITI)All r

8、ights reserved.No part of this publication may be reproduced in anyform, in an electronic retrieval system or otherwise,without prior written permission of ITI, 1250 Eye Street NW,Washington, DC 20005.Printed in the United States of AmericaANSI X3.158-1987 American National Standard for Information

9、Systems - Recorded Magnetic Tape Cassette for Information Interchange - 4 Track, 0.150 inch (3.8 1 mm), 8000 bpi (315 bpmm), Group Code Recording Secretariat Computer and Business Equipment Mgnufacturers Association Approved July 15,1987 American National Standards Institute, Inc Foreword (This Fore

10、word is not part of American National Standard X3.158-1987.) This standard presents the minimum requirements for the organization and location of magnetically encoded data on a 0.150-inch (3.8 1 -mm) -wide magnetic tape. These require- ments will allow parties that comply to reliably interchange inf

11、ormation. The standard applies to 4-track, 8000-bpi (3 15bpmm), serial, group-coded information using tape drives that operate in the streaming mode. The advantage of using the format described in this standard is that it provides far greater data capacities and higher data transfer rates than are p

12、rovided by existing formats. For example, this format allows 20 megabytes of formatted data to be recorded on a cassette meeting the requirements of the proposed American National Standard for Information Systems - Unrecorded Magnetic Tape Cassette for Information Interchange - 0.150 inch (3 8 1 mm)

13、, 10 000 ftpi (394 ftmm), ANSI X3.164 (under development), whereas previous formats allowed a maximum of 2 megabytes. This standard was developed by Technical Committee X3B5 on Digital Magnetic Tape. This group consists of experienced and qualified specialists on the recording of digital information

14、 on magnetic tape. In the development of this standard, careful consideration was given to current practices, existing equipment and supplies, achieving the broadest possible acceptance, and providing a basis for future improvement in the use of the medium. This standard was developed to meet indust

15、ry needs for small and inexpensive tape back- up systems. The tape drives are intended to be used for backup of the small, fmed-media, rigid disk drives used in personal computers. Suggestions for improvement of this standard will be welcome. They should be sent to the Computer and Business Equipmen

16、t Manufacturers Association, 3 11 First Street, NW, Suite 500, Washington, DC 20001. This standard was processed and approved for submittal to ANSI by the Accredited Stan- dards Committee on Information Processing Systems, X3. Committee approval of this standard does not necessarily imply that all c

17、ommittee members voted for its approval. At the time it approved this standard, the X3 Committee had the following members: Richard Gibson, Chair Donald C. Loughry, Vice-Chair Catherine A. Kachurik, Administrative Secretary Organization Represented American Library Association. . American Nuclear So

18、ciety. . AMP Incorporated Association of the Institute for Certification of Computer Professionals AT for the most recent information on its status and 1.2 Purpose 1.2.1 This standard defines the requirements and supporting test methds necessary to ensure interchange at acceptable performance levels

19、. It is distinct from a specification in that it delineates a minimum of restric- tions consistent with compatibility in interchange trans- actions. 1.2.2 The performance levels contained in this stan- dard represent the minimum acceptable levels of per- formance for interchange purposes. They, ther

20、efore, represent the performance levels that the interchanged items should meet or surpass during their useful life and thus define end-of-life criteria for interchange pur- poses. The performance levels in this standard are not intended to be employed as substitutes for purchase specifications. 1.2

21、3 Wherever feasible, quantitative performance levels that shall be met or exceeded in order to comply with this standard are given. In all cases, including those in which quantitiative limits for requirements falling within the scope of this standard are not stated but are left to agreement betwen i

22、nterchange parties, standard test methods and measurement procedures shall be used to determine such limits. 1.2.4 U.S. engineering units are the original dimen- sions in this standard. Conversions of toleranced dimen- sions from customary U.S. engineering units (similar to British Imperial Units) t

23、o SI units have been incorpor- ated in this standard in accordance with Method A as described in American National Standard Metric Prac- tice, ANSI/IEEE 268-1982, and in International Stan- dard for Toleranced Dimensions - Conversion from Inches into Millimetres and Vice Versa, IS0 370-1975, except

24、as noted. Method A should be used for economy unless a requirement for absolute assurance of a fit justifies use of Method B. In the national standards of IS0 member nations, additional rounding may be done 6 to produce “preferred” values. These values should lie within or close to the original tole

25、rance ranges. 1.2.5 Except as indicated in 1.2.3, interchange parties complying with the applicable standards should be able to achieve compatibility without need for addi- tional exchange of technical information. 2. Referenced and Related Standards 2.1 American National Standards. This standard is

26、 in- tended to be used in conjunction with the following American National Standards. When these referenced standards are superseded by a revision approved by the American National Standards Institute, Inc, the revision shall apply. ANSI X3.4-1986, Information Systems - Coded Char- acter Sets - 7-Bi

27、t American National Standard Code for Information Interchange (7-Bit ASCII) ANSI X3.54-1986, Information Systems - Recorded Magnetic Tape for Information Interchange (6250 CPI, Group-Coded Recording) ANSI/IEEE 268-1982, Metric Practice 2.2 Other Standard. This standard is also intended to be used in

28、 conjunction with International Standard for Toleranced Dimensions - Conversion from Inches into Millimetres and Vice Versa, IS0 370-1975.* 2.3 Related American National Standard ANSI X3.164, Information Systems - Unrecorded Magnetic Tape Cassette for Information Interchange - 0.150 Inch (3.84 mm),

29、8000 bpi (3 15 bpmm), GCR Encoded. 3. Definitions azimuth. The angular deviation, in minutes of arc, of the mean flux transition line from the line normal to jhe cassette reference plane. bit. A single digit in the binary number system. bit cell. A length of magnetic recording tape within which the

30、occurrence of a flux transition signifies a ONE bit and the absence signifies a ZERO bit. block. A group of 5 12 consecutive bytes transferred as a unit. Available from the American National Standards Institute, 1430 Broadway, New York, NY 10018. beginning-of-tape (ROT) marker. A single hole punched

31、 in the tape that indicates the start of the usable record- ing area in the forward direction. In the reverse direc- tion the BOT marker indicates the approaching end of the usable recording area (see Figure 1). bot. The physical beginning of tape (see Figure 1). byte. A group of 8 data (10 encoded)

32、 bits operated on as a unit. cassette. A 2-I/2 by 4-inch enclosure containing a 0.150-in (3.81-mm) -wide magnetic tape wound on two coplanar hubs. cyclic redundancy check (CRC). The check that is re- corded after the data block and preceding the postam- ble of each recorded block for the purpose of

33、error detection. density. The maximum allowable flux transitions per unit length for a specific recording standard. end-of-tape (EOT) marker. A single hole punched in the tape that indicates the approaching end of the usable recording area in the forward direction. The EOT Marker indicates the start

34、 of the usable recording area in the reverse direction (see Figure 1). eot. The physical end of tape (see Figure 1). erase. To remove all magnetically recorded information from the tape. fde mark. An identification mark following the last block in a file. flux transition. A point on the magnetic tap

35、e that exhibits maximum free-space flux density normal to the tape surface. flux transition spacing. The distance on the magnetic tape between flux transitions. group code recording (GCR). A data encoding method where a 4-bit group of data bits is encoded into a 5-bit group for recording on magnetic

36、 tape (see ANSI X3.54- 1986 for more information about this type of re- cording). magnetic tape. An oxide-coated mylar base tape capa- ble of accepting and retaining magnetically recorded information. nibble. A group of 4 binary (5 GCR) bits operated on as a unit. postamble. Guard information record

37、ed after the data block. preamble. Synchronization information recorded be- fore the data block. 7 AMERICAN NATIONAL STANDARD X3.158-1987 EOT EOT MARKER BOT MARKER BOT t t f t Y/A I i PD I - + c- I D D - D P R D P NOTE: R = Reference burst; P = Preamble; D = Data or control block. Minimum Maximum Di

38、mension (in) (mm) (in) (mm) Description Dl 0 0 15 381 Leader to start of track reference burst D2 -0.5 -12.7 4 102 BOT marker to end of track reference burst and start of preamble on even tracks D3 - - 36 915 EOT marker to end of data on even tracks D4 1 25.4 6 152 EOT marker to start of preamble on

39、 odd tracks D6 - - 27 686 BOT marker to end of data on odd tracks Figure 1 Tape Position Holes 8 AMERICAN NATIONAL STANDARD X3.158-1987 Table 1 Translation Table for Data Nibbles and GCR Nibbles HEX B3 B2 Bl BO G4 G3 G2 Gl GO HEX 0 0 0 0 0 c-* 1 1 0 0 1 19 1 0 0 1 - 1 1 0 2 0 0” 1 0 - 1 0 0 1 1 1B 1

40、 0 12 3 0 0 1 1 - 1 0 0 1 1 13 4 0 1 0 0 - 1 1 1 1 5 0110-l olol-l: ; 1 ;: 6 1 0 16 7 0 1 1 1 - 1 0 1 1 1 17 8 1 1A 9 1 0 0 0 - 1 1 8 l O O l - A 1010-O O-i 0 ; 09 1 0 OA B 1 o I 1 - 0 1 0 1 1 OB C 1 1 0 0 - 1 1 1 1 0 1E DllOl-01; OD E 1110-01 ; OE F 1111-01 1 1 1 OF NOTE: GCR bit G4 is recorded fir

41、st recorded block. A group of consecutive bits comprising preamble, data block marker, data block, block address, CRC, and postamble. reference field. The minimum field that, when applied to the signal amplitude reference tape cassette, causes a signal output equal to 95% of the maximum signal outpu

42、t at the specified test density. reference tape cassette. A magnetic tape cassette se- lected for a specific property to be used as a reference. test recording current. A recording current between 128% and 132% of the current required to produce the reference field at 10 000 ftpi (394 ftpmm). typica

43、l field. The minimum field that, when applied to the tape under test, causes a signal output equal to 95% of the maximum signal output at the specified test density. signal amplitude reference tape cassette. A reference tape cassette selected as a standard for signal amplitude and reference field.3

44、standard reference amplitude. The average peak-to- peak signal amplitude output of the Signal Amplitude Reference Tape Cassette when it is recorded with the “A master standard amplitude reference tape wiu be estab- lished at the NBS. Secondary standard amplitude reference tapes are under considerati

45、on from the NBS, and the part number will be assigned when the tape is available. For more information, contact: Office of Standard Materials, Room B311, Chemistry Building, National Bureau of Standards, Washington, DC 20234. Until NBS tapes are available, interim secondary standard amplitude refere

46、nce tapes will be available from Verbatim Corporation, 323 Sequel Way, Sunnyvale,CA 94086, Part Number 86496. appropriate Test Recording Current on the NBS mea- surement system at each test physical recording density. The signal amplitude shall be averaged over a minimum of 10 000 flux transitions.

47、streaming. A method of recording on magnetic tape that maintains continuous tape motion without the re- quirement to start and stop within an inter-record gap. track. A longitudinal area on the tape along which a series of magnetic signals may be recorded. underrun. A condition developed when host t

48、ransmits or receives data at a rate less than that required by the device for streaming operation. 4. Recording 4.1 Method. The method of recording shall be the “non-return to zero, invert on one” (NRZI) where a ONE is represented by a flux transition occurring in the bit cell and a ZERO is represen

49、ted by the absence of a flux transition in the bit cell. 4.2 GCR Code. Each g-bit data byte is separated into two 4-bit groups (nibbles). Each 4-bit data nibble is encoded into a 5bit group code recording (GCR) nib- ble for recording on the streaming magnetic tape cas- sette. The most significant nibble is recorded first. The encoded data has the property that no more than two consecutive ZEROS shall occur. The translation table for data nibbles (B3, B2, Bl, BO) and GCR nibbles (G4, G3, G2, Cl, do) shall be as shown in Table 1. 9 AMERICAN NATIONAL STANDARD X3.158-1987 Figure 2 Flu