ANSI INCITS ISO 7487-3-1986 Information processing - Data interchange on 130 mm (5.25 in) flexible disk cartridges using modified frequency modulation recording at 7 958 ftprad I 9.pdf

1、International Standard ( 7487 / 3 0 1 4 a!ie ,NTEANAT,ONAL ORGANIZATION FOR STANDARDIZATION*ME)I(nYHAPOnHAR OPrAHH3Al,MR fl0 CTAHAAPTH3AUIIM.ORGANlSATlON INTERNATIONALE DE NORMALISATION Information processing - Data interchange on 130 mm (5.25 in) flexible disk cartridges using modified frequency mo

2、dulation recording at 7 958 ftprad, I,9 tpmm (48 tpi), on both sides - Part 3 : Track format B Traitement de Iinformation - 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) At present at the stage

3、 of draft. 1 IS0 7487/3-1986 (E) 4.1.2 Track location tolerance of the recorded flexible disk cartridge The centrelines of the recorded tracks shall be within f 0,685 mm (0.603 3 in) of the nominal positions, over the range of operating environment specified in IS0 7487/l. This tolerance corresponds

4、 to twice the standard deviation. 4.1.3 Recording offset angle At the instant of writing or reading a magnetic transition, the transition shall have an angle of 0” f 18 with the radius. This tolerance corresponds to twice the standard deviation. 4.1.4 Density of recording 4.1.4.1 The nominal density

5、 of recording shall be 7 958 ftprad. The nominal bit cell length is 125,7 yrad. 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 nominal bit cell length. 4.1.4.3 The short-term average bit cell length, referr

6、ed to a particular bit cell, shall be the average of the lengths of the preceding eight bit cells. It shall be within I!I 8 % of the long- term average bit cell length. 4.1.5 Flux transition spacing (see figure 1) The instantaneous spacing between flux transitions may be in- fluenced by the reading

7、and writing process, the bit sequence recorded (pulse crowding effects), and other factors. The lo- cations of the transitions are defined as the locations of the peaks in the signal when reading. Tests should be carried out using a peak-sensing amplifier. 4.1.5.1 The spacing between the flux transi

8、tions in a se- quence of ONES shall be between 86 % and 120 % of the short-term average bit cell length. 4.1.5.2 The spacing between the flux transition for a ONE and that between two ZEROS preceding or following it shall be be- tween 136 % and 165 % of the short-term average bit cell length. 1 1 1

9、0 1 4.1.5.3 The spacing between the two ONE flux transitions surrounding a ZERO bit cell shall lie between 185 % and 225 % of the short-term average bit cell length. 4.1.5 Average signal amplitude For each side the average signal amplitude on any non- defective track (see IS0 7487/l) of the intercha

10、nged flexible disk cartridge shall be less than 160 % of SRAlfand more than 40 % of SRAzf. 4.1.7 Byte A byte is a group of eight bit-positions, identified Bl to B8, with B8 the most significant and recorded first. The bit in each position is a ZERO or a ONE. 4.1.8 Sector All tracks are divided into

11、9 sectors of 512 bytes. 4.1.9 Cylinder A pair of tracks, one on each side, having the same track number. 4.1 .I0 Cylinder number The cylinder number shall be a two-digit number identical with the track number of the tracks of the cylinder. 4.1.11 Data capacity of a track The data capacity of a track

12、 shall be 4 608 bytes. 4.1.12 Hexadecimal notation Hexadecimal notation shall be used hereafter to denote the following bytes : (00) for (88 to Bl) = 00000000 (01) for (88 to Bl) = 00000001 (4E) for (88 to Bl) = 01601110 (FE) for (88 to Bl) = 11111110 0 1 I 1 I I i 80% tolZO% 130% to 165% 130%to 165

13、% 185% to 225% e e Figure 1 IS0 7487/3-1966 (E) (FB) for (88 to Bl) = 11111011 (F8) for (88 to Bl) = 11111000 (Al)” for (B8 to Bl) = 10100001 In (Al )* the boundary transition between 83 and 84 is missing. 4.1.13 Error detection characters (EDC) The two EDC-bytes are hardware generated by shifting s

14、erially the relevant bits, specified later for each part of the track through a 16-bit shift register described by X16 + X12 + x5 + 1 (See also annex A.) 4.2 Track layout after the first formatting for all tracks After the first formatting, there shall be 9 usable sectors on each track. The layout o

15、f each track shall be as shown in figure 2. During formatting the rotational speed of the disk, averaged index to index, shall be 300 5 6 r/min. 4.2.1 Index gap At nominal density this field shall comprise not less than 32 bytes and not more than 146 bytes, the content of which is not specified exce

16、pt that there shall be no (Al )*-bytes. Writing the index gap is started when the index is detected. Any of the first 16 bytes may become ill-defined due to over- writing. 4.2.2 Sector identifier This field shall be as given in table 1. 4.2.2.1 Identifier mark This field shall comprise 16 bytes : 12

17、 (OOLbytes 3 (Al )*-bytes 1 (FE)-byte 4.2.2.2 Address identifier This field shall comprise 6 bytes. 4.2.2.2.1 Track address This field shall comprise 2 bytes : a) Cylinder number (C) This field shall specify in binary notation the cylinder number from 00 for the outermost cylinder to 39 for the inne

18、rmost cylinder. b) Side number (Side) This field shall specify the side of the disk. On side 0, it shall be (00) on all tracks. On side 1, it shall be (01) on all tracks. 4.2.2.2.2 Sector number (S) The 3rd byte shall specify in binary notation the sector number from 01 for the 1st sector to 9 for t

19、he last sector. The sectors may be recorded in any order of their sector numbers. Table 1 Sector identifier Identifier mark Address identifier Track address S EDC C Side 12 bytes 3 bytes 1 byte 1 byte 1 byte 1 byte 1 byte 2 bytes (00) (Al)” (FE) (00) or (02) (01) INDEX GAP SECTOR IDENTIFIER IDENTIFI

20、ER -1st Sector-I 9th Sector 4 Figure 2 3 IS0 7487/3-1985 (E) 4.2.2.2.3 4th byte The 4th byte shall always be a (02)-byte. 4.2.2.2.4 EDC These two bytes shall be generated as defined in 4.1 .I3 using the bytes of the sector identifier starting with the first (Al )*-byte (see 4.2.2.1) of the identifie

21、r mark and ending with the 4th byte (see 4.2.2.2.3) of the sector address. If the EDC is incorrect, then the sector is defective. IS0 9293 specifies the handling of defective sectors. 4.2.3 Identifier gap This field shall comprise 22 initially recorded (4E)Lbytes. These bytes may have become ill-def

22、ined due to overwriting. 4.2.4 Data block This field shall be as given in table 2. Table 2 4.2.4.1 Data mark This field shall comprise 12 (OOLbytes 3 (Al )*-bytes 1 (FB)-byte 4.2.4.2 Data field This field shall comprise 512 bytes. No requirements are implied beyond the correct EDC for the content of

23、 this field. 4.2.4.3 EDC These two bytes shall be generated as defined in 4.1.13 using the bytes of the data block starting with the first (Al )*-byte of the data mark (see 4.2.4.1) and ending with the last byte of the data field (see 4.2.4.2). If the EDC is incorrect, then the sector is defective.

24、IS0 9293 specifies the handling of defective sectors. 4.2.5 Data block gap This field shall comprise 80 initially recorded (4ELbytes. It is recorded after each data block and it precedes the following sector identifier. After the last data block, it precedes the track gap. 4.2.6 Track gap This field

25、 shall follow the data block gap of the last sector. (4E)-bytes are written until the index window is detected, unless it has been detected during writing of the last data block gap, in which case there shall be no track gap. 5 Coded representation of data 5.1 Standards The contents of the data fiel

26、d shall be recorded and interpreted according to the relevant International Standards for the coding of information. 5.2 Coding methods 5.2.1 When the coding method requires it, the data field shall be regarded as an ordered sequence of 8-bit bytes. Within each byte the bit positions shall be identi

27、fied by 88 to Bl. The high-order bit shall be recorded in position Bl. The sequence of recording shall be high-order bit first. When the data is encoded according to an 8-bit code, the binary weights of the bit positions shall be as shown in figure 3. When the data is encoded according to a 7-bit co

28、de, bit posi- tion 88 shall contain bit ZERO, and the data shall be encoded in bit positions 87 to Bl, using the same binary weights as shown in figure 3. 5.2.2 When the coding method requires it, the data field shall be regarded as an ordered sequence of bit positions, each con- taining a bit. Bit

29、position Binary weights 08 87 66 05 84 83 82 Bl 128 64 32 16 8 4 2 1 Figure 3 IS0 7467/3-1966 (El Annex A EDC implementation (This annex does not form part of the standard.) Figure 4 shows the feedback connections of a shift register which may be used to generate the EDC bytes. Prior to the operatio

30、n, all positions of the shift register are set to ONE. Input data are added (exclusive OR) to the contents of position C15 of the register to form a feedback. This feedback is in its turn added (exclusive OR) to the contents of position C4and position C,. On shifting, the outputs of the exclusive OR

31、 gates are entered respectively into positions Cc, C5 and CQ After the last data bit has been added, the register is shifted once more as specified above. The register then contains the EDC bytes. If further shifting is to take place during the writing of the EDC bytes, the control signal inhibits e

32、xclusive 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, the EDC bytes are also entered into the shift register as if they were data. After the final shift, the register con- tent

33、s will be all ZERO if the record does not contain errors. Control I Output 7 I Input (EDC writing) Figure 4 IS0 7467/3-1966 (E) Annex B Procedure and equipment for measuring flux transition spacing (This annex does not form part of the standard.) B.l General This annex specifies an equipment and a p

34、rocedure 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 interchange use. Testing shall be done on tracks 00 and 39 on both sides. The

35、test patterns 11011011 (DB) and 11011100 (DC) shall be written repeatedly on each test track. B.3 Test equipment B.3.1 Disk drive The disk drive shall have a rotational speed of 300 r/min, with a tolerance of * 3 r/min, averaged over one revolution. The average angular speed taken over 64 ps shall n

36、ot deviate by more than 0,5 % from the speed averaged over one revolution. B.3.2 Head B.3.2.1 Resolution The head shall have an absolute resolution of 55 % to 65 % at track 39 on each side, using the reference material RM 7487, applying the calibration factor of the reference material appropriate to

37、 the side, and recording with the appropriate test recording current. The resonant frequency of the head 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 B.3.3.1. 8

38、.3.2.2 Offset angle The head shall have a gap offset angle of O” f 6 with the disk radius on the testing 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 respo

39、nse from 1 000 to 187 500 Hz within If: 1 dB, and amplitude saturation shall not occur. 8.3.3.2 Peak sensing amplifier Peak sensing shall be carried out by a differentiating and limiting amplifier. 6 IS0 7487/3-1986 (E) 8.3.4 Time interval measuring equipment The time interval counter shall be able

40、to measure 4 f.s to at least 10 ns resolution. A triggering oscilloscope may be used for this purpose. B.4 Procedure for measurement 8.4.1 Flux transition spacing measurement The transition locations shall be measured by the locations of the peaks in the signal when reading. The flux transition spac

41、ing 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 all tracks Measure time intervals t, to r5 as shown in figure 5. DC 11011011110111001 4 +t- Figure 5 Sub-clause 4.1.5.1 corresponds to tl and t2. Sub-clause 4.1.5.

42、2 corresponds to t3 and te Sub-clause 4.1.5.3 corresponds to ts. 7 IS0 7487/3-1986 (E) Annex C Data separators for decoding MFM recording (This annex does not form part of the standard.) The MFM recording method gives nominal flux transition spacings of t for the patterns 1 1 or 0 0 0 3t/2 for the p

43、atterns 1 0 or 0 1 2t for the pattern 1 0 1 The data separator should be capable of resolving a difference of 2 f.s. To achieve this with a low error rate, the separator cannot operate 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.