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1、BRITISH STANDARD BS 5356-2: 1976 Specification for Magnetic single-disk cartridges (top loading) for data processing Part 2: Track format UDC 651.327.63 *1:621.3.037.3 Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 13:13:17 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5356-2:1976 This Briti
2、sh Standard, having been prepared under the direction of the Data Processing Industry Standards Committee, was published under the authority of the Executive Board on 31 August 1976 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference DPE/4 Draft for comm
3、ent 73/33646 DC and draft for approval 74/73056 ISBN 0 580 09194 5 Cooperating organizations The Data Processing Industry Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industri
4、al organizations: Aslib British Computer Society Ltd* British Paper and Board Industry Federation British Printing Industry Federation Business Equipment Trade Association* Civil Service Department, Central Computer Agency* Committee of London Clearing Bankers* Department of Industry, Computers, Sys
5、tems and Electronics Department of Industry, National Physical Laboratory Department of the Environment, Fire Research Station Electricity Supply Industry in England and Wales Electronic Engineering Association* Engineering Equipment Users Association Government Communication Headquarters HM Customs
6、 and Excise Institute of Cost and Management Accountants Institute of Municipal Treasurers and Accountants (Incorporated) Institution of Electrical and Electronics Technician Engineers Institution of Electrical Engineers* Institution of Mechanical Engineers London Transport Executive Ministry of Def
7、ence National Coal Board* National Computing Centre Ltd National Research Development Corporation Post Office* Society of British Aerospace Companies* The Government department and scientific and industrial organizations marked with an asterisk in the above list, together with the following were dir
8、ectly represented on the committee entrusted with the preparation of this British Standard: Data Processing Management Association Department of the Environment Institution of Electronic and Radio Engineers Radio and Electronic Component Manufacturers Federation Scientific Instrument Manufacturers A
9、ssociation Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 13:13:17 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5356-2:1976 BSI 12-1999i Contents Page Cooperating organizationsInside front cover Forewordii 1Scope1 2References
10、1 3Definitions1 4General requirements1 5Detailed description of track layout1 Appendix A CRC implementation5 Appendix B Rotational speed and clock frequency tolerance5 Appendix C Data capacity5 Appendix D Index slot detection tolerances5 Appendix E Factors affecting data interchange7 Figure 1 Genera
11、l track layout3 Figure 2 Sector zero layout4 Figure 3 Identifier layout (data sector)4 Figure 4 Data block layout4 Figure 5 CRC shift register4 Figure 6 Positions of last sector, track identifier and head relative to index6 Publications referred to8 Licensed Copy: sheffieldun sheffieldun, na, Mon De
12、c 04 13:13:17 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5356-2:1976 ii BSI 12-1999 Foreword This British Standard has been authorized by the Data Processing Industry Standards Committee. Work on magnetic disk packs began at the International Organization for Standardization (ISO) in 1968 with th
13、e setting up of a working group, now a subcommittee, under the secretariat of Germany. The first project to be undertaken, the standardization of a six-disk pack, has now been completed. Work on a British Standard for the six-disk pack went ahead simultaneously and resulted in the publication of BS
14、4850:1972 (Parts 1 and 2). Attention was then turned to projects dealing with a magnetic eleven-disk pack and a magnetic single-disk cartridge of the type which is loaded onto its drive spindle from the top. BS 5356-1 (based on ISO 3562) specifies the physical and magnetic characteristics and BS 535
15、6-2 (based on ISO 3563) specifies the track format of the single-disk cartridge; BS 5359 (based on ISO 3564) specifies the physical and magnetic characteristics of the eleven-disk pack. This British Standard is based on ISO 3563, to which it conforms in all essential particulars. The principle adopt
16、ed has been to specify those characteristics which are necessary for interchange, so that manufacturers will be able to retain some individual design features, whilst incorporating those essential for interchange. Although the parameters quoted have been based on existing materials and methods, wher
17、ever possible the use of alternatives which would maintain the original requirements has been permitted. Part 1 incorporates the mechanical and magnetic characteristics. This Part (Part 2) specifies a track format, detailing the patterns of magnetization on the disk surfaces to be used to record dat
18、a blocks. These blocks are of a fixed length of 256 bytes, providing a total data capacity of approximately 2 106 bytes per cartridge. The specified format is based on current practice; disks recorded according to this Part of the standard and also conforming to Part 1 of the standard may be used fo
19、r data interchange. Information within the data blocks is in 8-bit bytes. Use of the UK 7-bit data code (see BS 4730) is specified, but other codes structured in accordance with BS 4953 may be used by agreement. It should be noted that binary code in 8-bit groups is used for control characters (some
20、 groups are specified in hexadecimal notation for convenience). This may not be an ideal arrangement for some applications since control information is visible to operating system software, but it avoids the need to modify existing equipment; most control functions are usually implemented by hardwar
21、e. Certification. Attention is drawn to the certification facilities described on the inside back cover. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Stan
22、dard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorpor
23、ated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 13:13:17 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5356-2:1976 BSI 12-19991 1 Scope This Part of this British Standard specifies the mode of recording and a track
24、 format for interchange of data using magnetic single-disk cartridges (top loading). NOTETrack location and dimensions and the mechanical and magnetic properties of the disks are specified in BS 5356-1. 2 References The titles of the publications referred to in this standard are listed on page 8. 3
25、Definitions For the purposes of this Part of BS 5356 the definitions of BS 3527 and BS 4953 apply, together with the following. 3.1 sector a division of a track. A sector may be further subdivided 3.2 sector zero a sector containing information which defines the physical location and characteristics
26、 of a track 3.3 data sector a sector which is composed of an identifier and a data block 3.4 identifier part of a sector containing information which defines the physical location and characteristics of a sector 3.5 data block part of a sector in which information is recorded 3.6 gap the space betwe
27、en the various divisions of a track 3.7 byte (or octet) eight serial bits, identified as b8 to b1 with b8 as the most significant and recorded first (00)16 denotes a byte (or octet) with b8 to b1 = 00000000 (FF)16 denotes a byte (or octet) with b8 to b1 = 11111111 (CC)16 denotes a byte (or octet) wi
28、th b8 to b1 = 11001100 (09)16 denotes a byte (or octet) with b8 to b1 = 00001001 (0B)16 denotes a byte (or octet) with b8 to b1 = 00001011 (OF)16 denotes a byte (or octet) with b8 to b1 = 00001111 denotes a byte (or octet) with b8 to b1 = 11110010 Forthe clock transitions of b6 and b5 are missing. 3
29、.8 cyclic redundancy check (CRC) two bytes which are the remainder formed by dividing the relevant bytes defined later in this standard by the polynomial X16 + X15 + X2 + 1 (see Appendix A). They can be used for error checking when reading. 4 General requirements 4.1 Rotation speed and clock frequen
30、cy. The total tolerance on rotation speed and clock frequency shall not exceed 3 % (see Appendix B). 4.2 Mode of recording. The mode of recording shall be double frequency where the start of every bit cell is a clock transition. A ONE is represented by a transition between two clock transitions. At
31、a nominal rotation speed of 2 400 rev/min, the all zeros pattern shall consist of 2.50 106 transitions per second nominally, and the all ONES pattern shall consist of 5.0 106 transitions per second nominally. 4.3 Index. The index is the point which determines the beginning and the end of a track. Th
32、e location of the index is specified as a true position in Part 1 of this standard. 4.4 Track capacity. The capacity of a track shall be 62 500 + 1 933 1 821 bits (see Appendix C). 4.5 Track layout. The general track layout shall be as shown in Figure 1. 5 Detailed description of track layout 5.1 Se
33、ctor zero. The first sector following the index is unique in that it contains a track identifier and will therefore be described separately. Figure 2 shows the sector zero layout. F2()16 * F2()16 * Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 13:13:17 GMT+00:00 2006, Uncontrolled Copy, (c)
34、 BSI BS 5356-2:1976 2 BSI 12-1999 5.1.1 Index gap. The index gap is a gap preceding the track identifier and shall be written so that the start of the track identifier is located within 65 12.5 bytes from the index. It is also a requirement that when this gap is initially written, 65 bytes of (FF)16
35、 shall precede the track identifier. The first 25 bytes of (FF)16 may, as a result of interchange, be unreadable (see Appendix D). 5.1.2 Track identifier. The track identifier shall consist of 16 bytes as follows. 5.1.2.1 Synchronization (8 bytes) as follows. (00)16 (00)16 (00)16 (00)16 (FF)16(09)16
36、 5.1.2.2 F (Flag) (1 byte) is used to indicate defective and alternative tracks. The significance of the bits in this byte is as follows. The first two bits (b8 and b7) are always zero; b6 to b3 are reserved for future standardization and are also zero. 5.1.2.3 C (Cylinder) (2 bytes) specify in bina
37、ry the address of the cylinder. 5.1.2.4 H (Head) (1 byte) specifies in binary the address of a track within a cylinder. The byte can have the value 0 or 1. 5.1.2.5 NS (Number of sectors) (1 byte) specifies in binary the number of data sectors in a track, which for interchange purposes is twenty. 5.1
38、.2.6 Cyclic redundancy check (2 bytes). The bytes defined in 5.1.2.2 to 5.1.2.5 are divided by the polynomial specified in 3.9. 5.1.2.7 End. The track identifier ends with one byte (CC)16. 5.1.3 Track identifier gap. A 36 bytes gap of (FF)16 shall be initially recorded between the end of the track i
39、dentifier and the start of sector ONE. The contents of this gap may subsequently become undefined because of repeated writing operations. 5.2 Data sector 5.2.1 Identifier. Figure 3 shows the identifier layout. The identifier shall consist of 18 bytes as follows. 5.2.1.1 Synchronization (8 bytes) as
40、follows. (00)16 (00)16 (00)16 (00)16 (FF)16 (OB)16. 5.2.1.2 F (Flag) (1 byte) is used in each identifier for certain control and checking operations and can be used to indicate defective and alternative tracks. The significance of the bits in this byte is as follows. 5.2.1.3 C and H (Cylinder and he
41、ad) (3 bytes) are identical to those in sector zero except when appearing on defective or alternative tracks. On a defective track, cylinder and head bytes C and H contain the cylinder and head number of the alternative track if the flag bits b1 and b2 are 1,0 respectively. On an alternative track,
42、C and H contain the cylinder and head number of the defective track which it replaces. 5.2.1.4 S (Sector) (1 byte) is used to identify sectors on the track. The first sector after sector zero shall have S = 1, and the subsequent sectors shall be numbered consecutively. 5.2.1.5 DL (Data length) (2 by
43、tes) specify in binary the number of information bytes in the data sector. For interchange purposes the data length shall be 256 bytes. 5.2.1.6 Cyclic redundancy check (2 bytes). The bytes defined in 5.2.1.2 to 5.2.1.5 are divided by the polynomial specified in 3.9. 5.2.1.7 End. The identifier ends
44、with one byte of (CC)16. 5.2.2 Identifier gap. A 34-byte gap of (FF)16 shall be initially recorded between the end of the identifier block and the start of the data block. The contents of this gap may subsequently become undefined because of repeated writing operations. 5.2.3 Data block. The data bl
45、ock shall consist of (DL + 12) bytes, where DL is the number of information bytes (see 5.2.1.5). Figure 4 shows the data block layout. The data block shall be as follows. 5.2.3.1 Synchronization (8 bytes) as follows. (00)16 (00)16 (00)16 (00)16 (FF)16 (0F)16. b2 b1 = 00 indicates good original track
46、 b2 b1 = 01 indicates good alternative track b2 b1 = 10 indicates defective track, alternative has been allocated b2 b1 = 11 indicates defective track, no alternative has been allocated. F2()16 * F2()16 * F2()16 * F2()16 * b8 = 1 for the first sector following sector zero and alternate sectors there
47、after. b8 = 0 for the other sectors. b7 to b3 are reserved for future standardization and are each zero. b2 and b1 are specified in 5.1.2.2. F2()16 * F2()16 * Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 13:13:17 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5356-2:1976 BSI 12-19993 5.2.3.
48、2 Information. The information shall consist of a number of information bytes as specified in the DL portion of the identifier. For the purposes of data interchange in accordance with this standard, the data in these bytes shall be recorded in the UK 7-bit data code specified in BS 4730. However, by
49、 agreement between the sender and the recipient, data in some other 7-bit or 8-bit code structured in accordance with BS 4953 may be recorded. Announcement of the code used may be achieved by use of the appropriate escape sequence registered in accordance with BS 4953. Whichever code is used: a) a 7-bit coded character shall be recorded in the 7 least significant bit positions of each byte such that bits b7 to b1 of the coded character shall be recorded in positions b7 to b1 respectively as defined in 3.7. b8 shall be always zero. b) an 8-bit coded char
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