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1、International Standard b) a flux transition shall be written at each cell boundary between consecutive bit cells containing ZEROS. Exceptions to this are defined in 4.1.12. 1 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Stand
2、ards 1/9972545001 Not for Resale, 04/21/2007 09:13:03 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 8378/2-1986 (E) 4.1.2 Track location tolerance of the recorded flexible disk cartridge The centrelines of the recorded tracks shall be within +0,042 5 mm fO.001 7 in) o
3、f the nominal positions, over the range of operating environment specified in IS0 837811. 4.1.3 Recording offset angle At the instant of writing or reading a magnetic transition, the transition shall have an angle of O” + 18 with the radius. NOTE - As tracks may be written and overwritten at extreme
4、s of the tolerances given in 4.1.2 and 4.1.3, a band of old information may be left at one edge of the newly written data and would constitute unwanted noise when reading. It is, therefore, necessary to trim the edges of the tracks by erasure after writing. 4.1.4 Density of recording 4.1.4.1 The nom
5、inal density of recording shall be 7 958 ftprad. The nominal bit cell length for track 00, side 0 is 251 grad, and for all the other tracks it is 125,7 grad. 4.1.4.2 The long-term average bit cell length shall be the average bit cell length measured over a sector. It shall be within +3,5 % of the no
6、minal bit cell length. 4.1.4.3 The short-term average bit cell length, referred to a particular bit cell, shall be the average of the lengths of the preceding eight bit cells. It shall be within bit position 88 shall be recorded with bit ZERO. The relationship shall be as shown in figure 5. Each 8-b
7、it coded character shall be recorded in bit-positions 88 to Bl of a byte. The relationship shall be as shown in figure 6. 4.4.2 Good and bad cylinders A good cylinder is a cylinder which has both tracks formatted according to 4.4.4. A bad cylinder is a cylinder which has both tracks formatted accord
8、ing to 4.4.5. 4.4.3 Requirements for cylinders Cylinder 00 shall be a good cylinder and shall have no defective sectors on side 0. There shall be at least 77 good cylinders between cylinder 01 and cylinder 79. 4.4.4 Layout of the tracks of a good cylinder References to 4.2 are for track 00, side 0.
9、References to 4.3 are for all other tracks. 4.4.4.1 Index gap Description : see 4.2.1 and 4.3. I. 4.4.4.2 Sector identifier 4.4.4.2.1 Identifier mark Description: see 4.2.2.1 and 4.3.2.1. Bits of the 7-bit combination Bit-positions in the byte 0 b7 b6 b5 b4 b3 b2 bl 88 87 B6 85 84 83 82 Bl Figure 5
10、Bits of the a-bit combination b8 b7 b6 b5 b4 b3 b2 bl Bit-positions in the byte 88 87 B6 85 84 83 82 Bl Figure 6 6 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:13:03 MDTNo
11、reproduction or networking permitted without license from IHS -,-,- ISO8378/2-1986(E) 4.4.4.2.2 Address identifier For all other tracks, this field shall comprise Description: see 4.2.2.2 and 4.3.2.2. 4.4.4.2.2.1 Track address 12 (00).bvtes 3 (Al)*-bytes 1 byte This field shall comprise 2 bytes : Th
12、e 16th byte shall be a) Cylinder address (Cl This field shall specify in binary notation the cylinder address from 00 for the outermost cylinder to 77 for the innermost cylinder. NOTE - A unique cylinder number is associated with each cylinder (see 4.1.10). Two of these cylinders are intended for us
13、e only when there are one or two defective cylinders. Each good cylinder possesses a unique cylinder address : a defective cylinder does not possess a cylinder address. Cylinder addresses are assigned con- secutively to the good cylinders in the ascending sequence of cylinder numbers. b) Side number
14、 (Side) Description: see 4.2.2.2.1 and 4.3.2.2.1. 4.4.4.2.2.2 Sector number (S) Description: see 4.2.2.2.2 and 4.3.2.2.2 4.4.4.2.2.3 4th byte Description: see 4.2.2.2.3 and 4.3.2.2.3. 4.4.4.2.2.4 EDC Description: see 4.2.2.2.4 and 4.3.2.2.4. 4.4.4.2.3 Identifier gap Description: see 4.2.3 and 4.3.3.
15、 These bytes may have become ill-defined due to the overwriting process. 4.4.4.2.4 Data block 4.4.4.2.4.1 Data mark For track 00, side 0, this field shall comprise 6 UN)-bytes 1 byte The 7th byte shall be (FB)” indicating that the data are valid and that the whole data field can be read; (F8)” indic
16、ating that the 1st byte of the data field shall be interpreted according to IS0 7665. (FB) indicating that the data are valid and that the whole data field can be read; (F8) indicating that the 1st byte of the data field shall be interpreted according to IS0 7665. 4.4.4.2.4.2 Data field This field s
17、hall comprise 128 bytes or 256 bytes as specified in 4.2.4.2 and 4.3.4.2. If it comprises less than the requisite number of data bytes, the remaining positions shall be filled with UN-bytes. Data fields in cylinder 00 are reserved for operating system use, including labelling. 4.4.4.2.4.3 EDC Descri
18、ption: see 4.2.4.3 and 4.3.4.3. If the last byte of the data mark is (F8)” or (F8) and the 1st character of the data field is CAPITAL LETTER F, the EDC may or may not be correct, as the sector contains a defective area. If the 1st character is CAPITAL LETTER D, then the EDC shall be correct. On cyli
19、nder 00, only CAPITAL LETTER D shall be allowed. 4.4.4.2.5 Data block gap This field is recorded after each data block and it precedes the following sector identifier. After the last data block, it precedes the track gap. It comprises initially 27 fFF)-bytes (see 4.2.5) or 54 (4E)-bytes (see 4.3.5).
20、 These bytes may have become ill-defined due to the overwriting process. 4.4.4.2.6 Track gap Description : see 4.2.6 and 4.3.6. 4.4.5 Layout of the tracks of a bad cylinder 4.451 Contents of the fields The fields of the tracks of a bad cylinder should have the following contents : 4.4.5.1.1 Index ga
21、p Description : see 4.2.1 and 4.3.1. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:13:03 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 8378/2
22、-1986 (E) 4.4.5.1.2 Sector identifier This field should comprise an identifier mark and an address identifier. 4.4.5.1.2.1 Identifier mark This field should comprise 16 bytes : 12 WOLbytes 3 (Al )*-bytes 1 (FE)-byte These two EDC-bytes shall be generated as defined in 4.1 .I3 using the bytes of the
23、sector identifier starting with the first (Al)*-byte (4.4.5.1.2.1) of the identifier mark and ending with the above 4 (FFLbytes. 4.4.5.1.3 Other fields The contents of the remaining fields are not specified and may be ill-defined. 4.4.5.1.2.2 Address identifier This field should comprise 6 bytes 4 (
24、FFI-bytes 2 EDC-bytes 4.4.5.2 Requirements for tracks Each track of a bad cylinder shall have at least one of its sector identifiers with the content specified in 4.4.5.1.2. If this con- dition is not satisfied, the cartridge shall be rejected. Copyright International Organization for Standardizatio
25、n Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:13:03 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 8378/2-1986 (El Annex A EDC implementation (This annex does not form part of the standard.) Figure
26、 7 shows the feedback connections of a shift register which may be used to generate the EDC bytes. Prior to the operation, all positions of the shift register are set to ONE. Input data are added (exclusive OR1 to the contents of position C, of the register to form a feedback. This feedback is in it
27、s turn added (exclusive OR) to the contents of position C4and position CI1 . On shifting, the outputs of the exclusive OR gates are entered respectively into positions Ce, C5 and C12. After the last data bit has been added, the register is shifted once more as specified above. The register then cont
28、ains the EDC bytes If further shifting is to take place during the writing of the EDC bytes, the control signal inhibits exclusive OR operations. To check for errors when reading, the data bits are added into the shift register in exactly the same manner as they were during writing. After the data,
29、the EDC bytes are also entered into the shift register as if they were data. After the final shift, the register contents will be all ZERO if the record does not contain errors. Control output J Input (EDC writing) Figure 7 9 Copyright International Organization for Standardization Provided by IHS u
30、nder license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:13:03 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 8378/2-l= (El Annex B Procedure and equipment for measuring flux transition spacing (This annex does not form part of
31、 the standard.) B.l General This annex specifies an equipment and a procedure for measuring flux transition spacing on 130 mm (5.25 in) flexible disk cartridges using MFM recording at 7 958 ftprad on both sides. B.2 Format The disk to be measured shall be written by the disk drive for data interchan
32、ge use. Testing shall be done on tracks 00 and 79 on both sides. Track 00, side 0 shall have the test patterns 001OOOOO (20) and 11101111 (EF) written repeatedly. Track 79, side 0, and tracks 00 and 79, side 1, shall have the test patterns 11011011 (DB) and 11011100 (DC) written repeatedly. B.3 Test
33、 equipment B.3.1 Disk drive The disk drive shall have a rotational speed of 300 r/min, with a tolerance of f3 r/min, averaged over one revolution. The average angular speed taken over 64 ys shall not deviate by more than 0,5 % from the speed averaged over one revolution. 8.3.2 Head 8.3.2.1 Resolutio
34、n The head shall have an absolute resolution of 55 % to 65 % at track 79 on each side, using the reference material RM 7487, applying the calibration factor of the reference material appropriate to the side, and recording with the appropriate test recording current. The resonant frequency of the hea
35、d shall be at least 250 000 Hz. The resolution shall not be adjusted by varying the load impedance of the head. The resolution shall be measured at the output of the amplifier defined in 8.3.3.1. B.3.2.2 Offset angle The head shall have a gap offset angle of O” + 6 with the disk radius on the testin
36、g drive. 8.3.2.3 Contact Care shall be taken that the heads are in good contact with the media during the tests. B.3.3 Read channel 8.3.3.1 Read amplifier The read amplifier shall have a flat response from 1 000 to 187 500 Hz within f 1 db, and amplitude saturation shall not occur. B.3.3.2 Peak sens
37、ing amplifier Peak sensing shall be carried out by a differentiating and limiting amplifier. 10 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:13:03 MDTNo reproduction or net
38、working permitted without license from IHS -,-,- IS0 8378/2-1986 (E) B.3.4 Time interval measuring equipment The time interval counter shall be able to measure 4 us to at least 10 ns resolution. A triggering oscilloscope may be used for this purpose. B.4 Procedure for measurement B.4.1 Flux transiti
39、on spacing measurement The transition locations shall be measured by the locations of the peaks in the signal when reading. The flux transition spacing shall be measured by the pulse timing intervals after the read channel amplifier defined in 8.3.3. B.4.2 Flux transition spacing for track 00, side
40、0 Measure time intervals tl to fa as shown in figure 8. B.4.3 Flux transition spacing for all other tracks Measure time intervals tl to t5 as shown in figure 9. 11 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972
41、545001 Not for Resale, 04/21/2007 09:13:03 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO8378/2-1986(E) 20 EF f c f A 0010000011101111 Sub-clause 4.1.5.1.1 corresponds to t1 and t2 Sub-clause 4.1.5.1.2 corresponds to t3 and t4 Sub-klause 4.1.5.1.3 corresponds to t5, t6
42、, 1, and t8 Figure 8 11011011110111001 Sub-clause 4.1.5.2.1 corresponds to t, and t2 Sub-clause 4.1.5.2.2 corresponds to t3 and t4 Sub-clause 4.1.5.2.3 corresponds to t5 Figure 9 12 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technica
43、l Standards 1/9972545001 Not for Resale, 04/21/2007 09:13:03 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO8378/2-1986(E) Annex C Data separators for decoding MFM recording (This annex does not form part of the standard.) C.l On track 00, side 0 the two-frequency recor
44、ding results in nominal flux transition periods of t for a ONE cell 2t for a ZERO cell where t = 4 us. The data separator should be capable of resolving a difference of 4 us. This can be achieved satisfactorily by the use of a digital data separator, or one using a fixed timer. c.2 On all other trac
45、ks, the MFM recording method gives nominal flux transition spacings of t for the patterns 1 1 or 0 0 0 3t/2 for the patterns 1 0 or 0 1 2t for the pattern 1 0 1 The data separator should be capable of resolving a difference of 2 us. To achieve this with a low error rate, the separator cannot operate
46、 on a fixed period but should follow changes in the bit cell length. It is recognized that various techniques may be developed to achieve dynamic data separation; with present technology only an analogue data separator based on a phase-locked oscillator can provide the necessary reliability. 13 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:13:03 MDTNo reproduction or networking permitted without license from IHS -,-,-