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1、INTERNATIONAL STANDARD 3561 INTERNATIONAL ORGANIZATION FOR STANDARDlZATlON .MEY,lYHAPOnHAI OPrAHM3AUHR no CTAHDAPTM3AUCIH .ORGANISATION INTERNATIONALE DE NORMALlSATlON Information processing - Interchangeable magnetic six-disk pack - Track format Traitemen t de Iin forma tion - Chargeur interchangea
2、ble Ei six disques magnetiques - Schkma de pis te First edition - 1976-06-15 w UDC 681.327.63 x Ref. No. IS0 3561-1976 (E) m 7 5 Descriptors : data processing, magnetic storage, disk packs, recording tracks, specifications, dimensions. z 0 E Price based on 9 pages Copyright International Organizatio
3、n for Standardization Provided by IHS under license with ISO Licensee=Defense Supply Ctr/9960866100 Not for Resale, 04/24/2007 10:59:10 MDTNo reproduction or networking permitted without license from IHS -,-,- FOREWORD IS0 (the International Organization for Standardization) is a worldwide federatio
4、n of national standards institutes (IS0 Member Bodies). The work of developing International Standards is carried out through IS0 Technical Committees. Every Member Body interested in a subject for which a Technical Committee has been set up has the right to be represented on that Committee. Interna
5、tional organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. Draft International Standards adopted by the Technical Committees are circulated to the Member Bodies for approval before their acceptance as International Standards by the IS0 Council. Internat
6、ional Standard IS03561 was drawn up by Technical Committee ISO/TC 97, Computers and information processing, and was circulated to the Member Bodies in March 1975. It has been approved by the Member Bodies of the following countries : Belgium Japan Czechoslovakia New Zealand France Poland Germany Rom
7、ania Hungary South Africa, Rep. of Italy Switzerland Turkey United Kingdom U.S.S.R. Yugoslavia No Member Body expressed disapproval of the document. 0 International Organization tor Standardization, 1976 l Printed in Switzerland Copyright International Organization for Standardization Provided by IH
8、S under license with ISO Licensee=Defense Supply Ctr/9960866100 Not for Resale, 04/24/2007 10:59:10 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD IS0 3561-1976 (Ej Information processing - Interchangeable magnetic six-disk pack - Track format 1 SCOP
9、E AND FIELD OF APPLICATION This International Standard specifies the track format characteristics for the six-disk pack to be used for data interchange (see IS0 2864). The 7-bit coded character set specified in IS0 646 has been adopted, though, by agreement between the interchange parties, the 7-bit
10、 or 8-bit extensions specified In IS0 2022 may be used. 2 GENERAL REQUIREMENTS 2.1 Rotation speed and clock period The total tolerance on rotation speed and clock period shall not exceed i 2,4 % (see annex A). 2.2 Mode of recording The mode of recording shall be double frequency where the start of e
11、very bit cell is a clock transition. A ONE is tepresented by a transition between two clock transitions. At the nominal rotation speed of 2 400 rev/min, the all-ZERO pattern consists of 1.25 x 106 transitions per second nominally, and an all-ONES pattern consists of 2.50 x 106 transitions per second
12、 nominally. 2.3 Index The index is a point which defines the beginning and the end of a track. Its location is specified as a true position in 5.1.2.5 of IS0 2864. 2.4 Track capacity The capacity of a track is 31 250 t ;!$ bits. 2.5 Track layout Figure 1 shows the general track layout (see also anne
13、x B). 3 DEFINITIONS 3.1 sector : A track is divided into sectors. A sector may be further subdivided. 3.2 home address : The home address contains informa- tion which defines the physical location and characteristics of a track. 3.3 count : The count contains information which defines the physical l
14、ocation and characteristics of a sector. 3.4 key : Part of a sector in which information is recorded; its use is optional. 3.5 data block : Part of a sector in which information is recorded. 3.6 gap : The space between the various divisions of a track. 3.7 byte (or octet) : Eight serial bits, identi
15、fied 88 to Bl with 88 as the most significant and recorded first. 3.8 hexadecimal notation : (OO), a denotes a byte (or octet) with B8 to Bl = 00000000 (FF), 6 denotes a byte (or octet) with B8 to Bl = 11111111 (OE),6 denotes a byte (or octet) with B8 to Bl = 00001110 (CC), denotes a byte (or octet)
16、 with B8 to Bl = 11001100 4 DETAILED DESCRIPTION OF TRACK LAYOUT 4.1 Sector 0 The first sector following index is unique in that it contains a home address and will therefore be described separately. 4.1 .I index gap (see figure 2) This is a gap preceding the home address and shall be written so tha
17、t the start of the home address is located within 30 -* 7 bytes from index. It is also a requirement that when this gap is initially written, 30 bytes of (OO),e shall precede the home address. The first 14 bytes of too),6 may, as a result of interchange, be unreadable (see annex C). 4.1.2 Home addre
18、ss (see figure 2) The home address consists of 14 bytes as follows : 4.1.2.1 Synchronization (6 bytes) as follows : (OO),rj (00),6 (00),6 (00116 (FF), (OE), 4.1.2.2 F - Flag (I byte). This is used to indicate defective and alternative tracks. The significance of the bits in this byte is as follows :
19、 The first two bits (88 and B7) are always ZERO. B6 to B3 are reserved for future standardization and are all ZERO. 1 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Defense Supply Ctr/9960866100 Not for Resale, 04/24/2007 10:59:10 MDTNo repro
20、duction or networking permitted without license from IHS -,-,- IS0 3561-1976 (E) 62 Bl = 00 indicates good original track. B2 Bl = 01 indicates good alternative track. B2 Bl = 10 indicates defective track, alternative has been allocated. 82 Bl = 11 indicates defective track, no alternative has been
21、allocated. 4.1.2.3 C - Cylinder (2 bytes). These specify in binary the address of the cylinder. The first bvte is always ZERO. The second byte can have any value in the range 0 to 202. 4.1.2.4 H - Head (2 bytes). These specify in binary the address of a track within a cylinder. The first byte is alw
22、ays ZERO. The second byte can have any value in the range 0 to 9. 4.1.2.5 CRC - Cyclic redundancy check (2 bytes). These consist of the ONES complement of the remainder obtained after dividing the previous five information bytes by the code polynomial (1 +x16). They can be used for error checking wh
23、en reading. 4.1.2.6 The home address ends with one byte (CC),. 4.1.3 Home address gap An 11-byte gap of (OO)ta is initially recorded between the end of the home address and the start of the count. The content of this gap may subsequently become undefined because of repeated writing operations. 4.1.4
24、 Count of Sector 0 (see figure 3) The count consists of 18 bytes as follows : 4.1.4.1 Synchronization (6 bytes) as follows : (00),6 (00),j (00),tj too),6 (f=F),6 toa, 4.1.4.2 F - Flag (1 byte). This is used for certain control and checking operations and is also used to indicate defective and altern
25、ative tracks. The significance of the bits in this byte is as follows : B8 -This is ZERO for Sector 0. See 4.2.1 for the use of this bit in other sectors. 87 -This is ZERO for Sector 0. See 4.2.1 for the use of this bit in other sectors. B6 to B3 are reserved for future standardization and are all Z
26、ERO. B2 and Bl - The state of these bits must always be the same as those in the home address (see 4.1.2.2). 4.1.4.3 C and H - Cylinder and Head (4 bytes). These bytes are identical to those in the home address except when appearing on defective or alternative tracks. On a defective track, C and H c
27、ontain cylinder and head number of the alternative track which replaces it. On an alternative track, C and H contain cylinder and head number of the defective track which it replaces. 2 4.1.4.4 S - Sector (1 byte). It is used to identify sectors on the track. 4.1.4.5 KL - Key length (1 byte). This s
28、pecifies in binary the number of information bytes in the key. 4.1.4.6 DL - Data length (2 bytes). These specifiy in binary the number of information bytes in the data block. 4.1.4.7 CRC - Cyclic redundancy check (2 bytes). These consist of the ONES complement of the remainder obtained after dividin
29、g the previous nine information bytes by the code polynomial (1 -I- x16). They can be used for error checking when reading. 4.1.4.8 The count ends with one byte (CC) 1 e 4.1.5 Count gap An 1 l-byte gap consisting of 9 bytes of (FF), e followed by 2 bytes of (OO)le is initially recorded between the e
30、nd of the count and the start of the key. The contents of this gap may subsequently become undefined because of repeated writing operations. 4.1.6 Key (see figure 4) The key consists of (KL + 9) bytes, where KL is the number of information bytes (see 4.1.4.5). If KL in the preceding count is ZERO, t
31、he key and the following gap (4.1.7) are omitted and the count is followed by the data block (see 4.1.8). Otherwise the follows : 4.1.6.1 Synchronization (6 bytes) as follows : (oo), 6 (00),j too), 6 (00116 (FF),6 key is as (OE),6 4.1.6.2 Information - This consists of a number of information bytes
32、as specified in the KL portion of the preceding count. The data in these bytes shall be recorded in the 7-bit coded character set in accordance with IS0 646. However, by agreement between the interchange parties, data in some other 7-bit or 8-bit code structured in accordance with IS0 2022 may be re
33、corded. A 7-bit coded character shall be recorded so that the bits b7 to bl of the coded character appear in positions B7 to Bl respectively (see 3.7); B8 shall be always ZERO. An 8-bit coded character shall be recorded so that bits a8 to al of the coded character are recorded in positions B8 to Bl
34、respectively. 4.1.6.3 CRC - Cyclic redundancy check (2 bytes). These consist of the ONES complement of the remainder obtained after dividing the previous information bytes by the code polynomial (1 +x16). They can be used for error checking when reading. 4.1.6.4 The key ends with one byte (CC),. Cop
35、yright International Organization for Standardization Provided by IHS under license with ISO Licensee=Defense Supply Ctr/9960866100 Not for Resale, 04/24/2007 10:59:10 MDTNo reproduction or networking permitted without license from IHS -,-,- 4.1.7 Key gap An 1 l-byte gap consisting of 9 bytes of (FF
36、),e followed by 2 bytes of (OO),a is initially recorded between the end of the key and the start of the data block. The contents of this gap may subsequently become undefined because of repeated writing operations. 4.1.8 Data block (see figure 5) The data block consists of (DL + 9) bytes, where DL i
37、s the number of information bytes (see 4.1.4.6). If DL in the preceding count is ZERO, the data block does appear in rudimentary form. The data block is as follows : IS0 3561-1976 (E) 4.2 Subsequent sectors 4.1.8.1 Synchronization (6 bytes) as follows : too), 6 too), 6 (00116 (00) 16 (FF),6 (OE), 4.
38、1.8.2 Information - This consists of a number of information bytes as specified in the DL portion of the preceding count. When this is ZERO, one byte (OO),e is recorded. The data in these bytes shall be recorded in the 7-bit coded character set in accordance with IS0 646. However, by agreement betwe
39、en the interchange parties, data in some other 7-bit or 8-bit code structured in accordance with IS0 2022 may be recorded. A 7-bit coded character shall be recorded so that bits b7 to bl of the coded character appear in positions B7 to Bl respectively (see 3.7); 88 shall always be ZERO. An 8-bit cod
40、ed character shall be recorded so that bits a8 to al of the coded character are recorded in positions B8 to Bl respectively. 4.1.8.3 CRC - Cyclic redundancy check (2 bytes). These consist of the ONES complement of the remainder obtained after dividing the previous information bytes by the code polyn
41、omial (I+ x16). They can be used for error checking when reading. If DL = 0 these two bytes may be missing. 4.1.8.4 The data block ends with one byte (CC),. If DL = 0 this byte may also be missing. 4.1.9 Data block gap The gap between the end of the data block and the start of the next sector is ini
42、tially recorded with (FF),e. Its initial length is : . (KL + DL) bytes Any fraction is truncated. KL - is the number of information bytes in the key. DL - is the number of information bytes in the data block. The contents of this gap may subsequently become undefined because of repeated writing oper
43、ations. The length of the gap may vary due to repeated writing operations; however, a minimum of 21 bytes shall always be present. 4.2.1 Count (see figure 6) The count of subsequent sectors consists of 20 bytes as follows : 4.2.1 .l Synchronization (8 bytes) as follows : (00), (00),6 (00116 (00116 (
44、FF),6 (FF);, (FF);, (OE), For !FF)y6 the clock transitions preceding the first five data transitions are missing. 4.2.1.2 F - Flag (1 byte). This is used in each count for certain control and checking operations and can be used to indicate defective and alternative tracks. The significance of the bi
45、ts in this byte are as follows : B8 = 1 for the first sector following the Sector 0 and alternate sectors thereafter, and B8 = 0 for the other sectors, B7 = 1 indicates that the sector is an overflowing sector, i.e. the information in the associated data block is continued in another sector. Otherwi
46、se this bit must be 0. B6 to B3 are reserved for future standardization and are all ZERO. B2 to Bl : see count of Sector 0 (4.1.4). 4.2.1.3 The remainder of the count is as described in4.1.4.3to4.1.4.8. 4.2.2 Remainder of sector The remainder of the sector is as described in 4.1.5 to 4.1.9 except fo
47、r the last sector. 4.3 Last sector 4.3.1 Count See 4.2.1. 4.3.2 Remainder of sector The remainder of the last sector except for the last gap is described in 4.1.5 to 4.1.8. 4.3.3 Last sector gap The gap following the last sector will be initially recorded as (FF), a to within * 7 bytes of index. It
48、is also a requirement that the end of the last sector be located 20 + 7 bytes before index when the track is recorded to the maximum capacity (see annex B) under worst-case conditions of disk speed and clock period (see also annex C). 3 Copyright International Organization for Standardization Provid
49、ed by IHS under license with ISO Licensee=Defense Supply Ctr/9960866100 Not for Resale, 04/24/2007 10:59:10 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 3561-1976 (E) Index Index Index G -Gap HA - Home address c -count K - Key D - Data block FIGURE 1 - General track layout 30.byte gap nominal (00)16 4 bytes 1 byte 1 byte FCCHH 2 bytes 1 byte 11 -byte gap 0)16