1、International Standard $ 7487/2 0 a 4 4! b) a flux transition shall be written at each cell boundary between consecutive bit cells containing ZEROs, 1 IS0 7487/2-1985 (El Exceptions to this are defined in 4.1.12. 4.1.2 Track location tolerance of the recorded flexible disk cartridge The centrelines
2、of the recorded tracks shall be within f 0,085 mm (0.003 3 in) of the nominal positions, over the range of operating environment specified in IS0 7487/l. This tolerance corresponds to twice the standard deviation. 4.1.3 Recording offset angle At the instant of writing or reading a magnetic transitio
3、n, the transition may 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 of recording shall be 7 958 ftprad. The nominal bit cell length for track 00, side 0 is 251 urad, and for all the other tr
4、acks it is 125,5 urad. 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 I!I 3,5 % of the nominal 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 th
5、e lengths of the preceding eight bit cells. It shall be within f 8 % of the long- term average bit cell length. 4.1.5 Flux transition spacing The instantaneous spacing between flux transitions may be in- fluenced by the reading and writing process, the bit sequence recorded (pulse crowding effects),
6、 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 Flux transition spacing for track 00, side 0 (see figure I) 4.1.5.1.1 The spacing between two clock flux tr
7、ansitions sur- rounding a data flux transition or between two data flux tran- L 9oxto 140% J sitions surrounding a clock flux transition shall be between 90 % and 140 % of the nominal bit cell length. 4.1.5.1.2 The spacing between two clock flux transitions not surrounding a data flux transition or
8、between two data flux transitions surrounding a missing clock flux transition shall be between 60 % and 110 % of the nominal bit cell length. 4.1.5.1.3 The spacing between a data flux transition and the preceding clock flux transition (when not missing) or between a clock flux transition and the pre
9、ceding data flux transition (when not missing) shall be between 45 % and 70 % of the nominal bit cell length. 4.1.5.2 Flux transition spacing for all tracks other than track 00, side 0 (see figure 2). 4.1.5.2.1 The spacing between the flux transitions in a se quence of ONEs shall be between 80 % and
10、 120 % of the short-term average bit cell length. 4.1.5.2.2 The spacing between the flux transition for a ONE and that between two ZEROs preceding or following it shall be between 130 % and 165 % of the short-term average bit cell length. 4.1.5.2.3 The spacing between the two ONE flux transitions su
11、rrounding a ZERO bit cell shall lie between 185 % and 225 % of the short-term average bit cell length. 4.1.6 Average signal amplitude For each side the average signal amplitude on any non- defective track (see IS0 7487/l) of the interchanged flexible disk cartridge shall be less than 160 % of SRAlfa
12、nd more than 40 % of SRAzf. 4.1.7 Byte A byte is a group of eight bit-positions, identified Bl to 88, with 88 the most significant and recorded first. The bit in each position is a ZERO or a ONE. C C 90 % to 140% 60% to 110% Figure 1 IS0 7487/2-1985 (El I 80% to 120% 130% to 165% 130% to 165 O/o 185
13、% to 225% - Figure 2 4.1.8 Sector All tracks are divided into 16 sectors. 4.1.9 Cylinder A pair of tracks, one on each side, having the same track number. 4.1.10 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
14、 capacity of a track The data capacity of track 00, side 0 shall be 2 048 bytes. The data capacity of all tracks other than track 00, side 0 shall be 4 096 bytes. 4.1.12 Hexadecimal notation Hexadecimal notation shall be used hereafter to denote the following bytes : (00) for (88 to Bl) = 00000000 (
15、01) for (B8 to Bl) = 00000001 (FF) for (88 to Bl) = 11111111 (FE)” for (88 to Bl) = 11111110 where the clock transitions of B6, B5 and 84 are missing (FBI” for (88 to Bl) = 11111011 where the clock transitions of B6, 85 and 84 are missing (F8)” for (B8 to Bl) = 11111000 where the clock transitions o
16、f B6, 85 and B4 are missing (4E) for (B8 to Bl) = 01001110 (FE) for (88 to Bl) = 11111110 (FBI for (B8 to Bl) = 11111011 (F8) for (88 to Bl) = 11111000 (Al)” for (88 to Bl) = 10100001 where the boundary transition between B3 and 84 is miss- ing. 4.1.13 Error detection characters (EDC) The two EDC-by
17、tes are hardware generated by shifting serially the relevant bits, specified later for each part of the track, through a 16-bit shift register described by Xl6 + x12 + x5 + 1 (See also annex A.) 4.2 Track layout after the first formatting for track 00, side 0 After first formatting, there shall be 1
18、6 usable sectors on the track. The layout of the track shall be as shown in figure 3. During formatting the rotational speed of the disk, averaged index to index, shall be 300 f 6 r/min. 4.2.1 Index gap At nominal density, this field shall comprise 16 (FFI-bytes. Writing the index gap is started whe
19、n the index hole is detected. Any of the first 8 bytes may be ill-defined due to subsequent overwriting. 3 IS0 7487/2-1985 (E) INDEX SECTOR GAP IDENTIFIER IDENTIFIER GAP FIRST DATA BLOCK DATA BLOCK GAP LAST DATA BLOCK DATA BLOCK GAP TRACK GAP bp lst Sector -4 - - - 16th Sector - - - 4 Figure 3 4.2.2
20、 Sector identifier This field shall be as given in table 1. Table 1 Sector identifier Identifier mark Address identifier Track address S EDC C Side 6 bytes 1 byte 1 byte 1 byte 1 byte 1 byte 2 bytes (00) (FE)” (00) (00) (00) 4.2.2.1 Identifier mark This field shall comprise 7 bytes : 6 (OOI-bytes 1
21、(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 two bytes : a) Cylinder address (Cl This field shall specify in binary notation the cylinder ad- dress. It shall be (00) for all sectors. b) Side number (Side) This field shall
22、specify the side of the disk. It shall be (00) for all sectors. 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 16 for the last sector. The 16 sectors shall be recorded in the natural order : 1, 2, 3, . . . . 15, 16 4.2.2.2.3
23、4th byte of the sector address The 4th byte shall always be a (OOLbyte. 4 4.2.2.2.4 EDC These two bytes shall be generated as defined in 4.1.13 using the bytes of the sector identifier starting with the (FE)*-byte (see 4.2.2.1) of the identifier mark and ending with the 4th byte (see 4.2.2.2.3) of t
24、he sector address. 4.2.3 Identifier gap This field shall comprise 11 initially recorded (FFI-bytes. 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 6 (OOLbytes 1 (FBI*-byte 4.2.4.2 Data field This field shall comprise 128 bytes. No requir
25、ements are implied beyond the correct EDC for the content of this field (see also 4.4.4.2.4.2). 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 7th byte of the data mark (see 4.2.4.1) and ending with the last byte of the data fi
26、eld (see 4.2.4.2). 4.2.5 Data block gap This field shall comprise 27 initially recorded (FFI-bytes. It is recorded after each data block and it precedes the following sector identifier. After the last data block, it precedes the track gap. IS0 7487/2-1985 (E) 4.2.6 Track gap 4.3.2.2.1 Track address
27、This field shall follow the data block gap of the 16th sector. (FF)-bytes are written until the index hole is detected, unless it has been detected during writing of the last data block gap, in which case there shall be no track gap. This field shall comprise 2 bytes a) Cylinder address (C) 4.3 Trac
28、k layout after the first formatting for all tracks other than track 00, side 0 After the first formatting, there shall be 16 usable sectors on each track. The layout of each track shall be as shown in figure 4. This field shall specify in binary notation the cylinder ad- dress from 00 for the outerm
29、ost cylinder to 37 for the inner- most cylinder. b) Side number (Side) During formatting the rotational speed of the disk, averaged index to index, shall be 300 + 6 r/min. 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 tra
30、cks. 4.3.1 Index gap At nominal density, this field shall comprise 32 (4E)-bytes. Writing the index gap is started when the index hole is detected. Any of the first 16 bytes may be ill-defined due to subsequent overwriting. 4.3.2.2.2 Sector number (S) The 3rd byte shall specify in binary notation th
31、e sector number from 01 for the 1st sector to 16 for the last sector. The sectors shall be recorded in the natural order : 1, 2, 3, . . . . 15, 16 4.3.2 Sector identifier This field shall be as given in table 3. 4.3.2.2.3 4th byte The 4th byte shall always be a toll-byte. 4.3.2.1 Identifier mark Thi
32、s field shall comprise 16 bytes : 12 (OO)-bytes 4.3.2.2.4 EDC 3 (Al )*-bytes 1 (FE)-byte These two bytes shall be generated as defined in 4.1.13 using the bytes of the sector identifier starting with the first (Al )*-byte (see 4.3.2.1) of the identifier mark and ending with the 4th byte (see 4.3.2.2
33、.3) of the sector address. 4.3.2.2 Address identifier 4.3.3 Identifier gap This field shall comprise 6 bytes. This field shall comprise 22 initially recorded (4E)-bytes. Table 3 Sector identifier Identifier mark Address identifier Track address S EDC C Side 12 bytes 3 bytes 1 byte 1 byte 1 byte 1 by
34、te 1 byte 2 bytes 00) (Al)” (FE) (00) or (01) (01) INDEX GAP SECTOR IDENTIFIER IDENTIFIER GAP FIRST DATA BLOCK DATA BLOCK GAP LAST DATA BLOCK DATA BLOCK GAP TRACK GAP L- lSt Sector -_ - - - 16th Sector - - - - 4 Figure 4 5 IS0 7487/2-1985 (El 4.3.4 Data block 4.3.6 Track gap This field shall be as g
35、iven in table 4. This field shall follow the data block gap of the last sector. (4ELbytes are written until the index hole is detected, unless it has been detected during writing of the last data block gap, in which case there shall be no track gap. Table 4 Data block Data mark I Data field I EDC I
36、12 bytes 3 bytes (00) (Al )* 1 byte (FBI 266 bytes 2 bytes 4.3.4.1 Data mark This field shall comprise 12 (001-bytes 3 (Al)*-bytes 1 (FBI-byte 4.3.4.2 Data field This field shall comprise 256 bytes. No requirements are implied beyond the correct EDC for the content of this field (see also 4.4.4.2.4.
37、2). 4.3.4.3 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 4.3.4.1) and ending with the last byte of the data field (see 4.3.4.2). 4.3.5 Data block gap This field shall comprise 54 initially recor
38、ded (4E)-bytes. It is recorded after each data block and it precedes the following sector identifier. After the last data block, it precedes the track gap. 4.4 Track layout of a recorded flexible disk for data interchange 4.4.1 Representation of characters Characters shall be represented by means of
39、 the 7-bit coded character set (IS0 846) and, where required, by its 7-bit or 8-bit extensions (IS0 2022) or by means of the 8-bit coded character set (IS0 4873). Each 7-bit coded character shall be recorded in bit-positions 87 to Bl of a byte; bit position 88 shall be recorded with bit ZERO. The re
40、lationship shall be as shown in figure 5. Each 8-bit 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
41、 a cylinder which has both tracks formatted ac- cording 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 37 good cylinders be- tween cylinder 01 and cylinder 39. Bits of the 7-bit combination Bit-po
42、sitions in the byte 0 b7 b6 b5 b4 b3 b2 bl B8 87 B6 85 84 B3 82 Bl Figure 5 Bits of the 8-bit combination Bit-positions in the byte b8 b7 b6 b5 b4 b3 b2 bl B8 87 1 B6 85 84 83 82 Bl Figure 6 6 IS0 7487/2-1985 (El 4.4.4 Layout of the tracks of a good cylinder 4.4.4.2.4 Data block References to 4.2 ar
43、e for track 00, side 0. References to 4.3 are for all other tracks. 4.4.4.2.4.1 Data mark For track 00, side 0, this field shall comprise 4.4.4.1 Index gap 6 (OOI-bytes Description : see 4.2.1 and 4.3.1. 1 byte 4.4.4.2 Sector identifier The 7th byte shall be (FBI” indicating that the data is valid a
44、nd that the whole data field can be read; 4.4.4.2.1 Identifier mark Description : see 4.2.2.1 and 4.3.2.1 (F8)” indicating that the first byte of the data field shall be interpreted according to IS0 7665. 4.4.4.2.2 Address identifier For all other tracks, this field shall comprise Description : see
45、4.2.2.2 and 4.3.2.2. 12 (OOI-bytes 3 (Al )*-bytes 4.4.4.2.2.1 Track address 1 byte This field shall comprise 2 bytes : The 16th byte shall be a) Cylinder address (Cl (FBI indicating that the data is valid and that the whole data field can be read: This field shall specify in binary notation the cyli
46、nder ad- dress from 00 for the outermost cylinder to 37 for the inner- most cylinder. (F8) indicating that the first byte of the data field shall be interpreted according to IS0 7665. NOTE - A unique cylinder number is associated with each cylinder (see 4.1.10). Two of these cylinders are intended f
47、or use 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. 4.4.4.2.4.
48、2 Data field This field shall 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 (OO)-bytes. b) Side number (Side) Description : see 4.2.2.2.1 and 4.3.2.2.1 Data fields in cyl
49、inder 00 are reserved for operating system use, including labelling. 4.4.4.2.2.2 Sector number (S) 4.4.4.2.4.3 EDC Description : see 4.2.2.2.2 and 4.3.2.2.2. Description : see 4.2.4.3 and 4.3.4.3. 4.4.4.2.2.3 4th byte 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. Description : see 4.2.2.2.3 and 4.3.2.2.3. 4.4.4.2.2.4 EDC On cylinder 00, only CAPITAL LETTER D shall be allowed
