1、INTERNATIONAL STANDARD ISOIIEC 1863 Second edition 19904541 Information processing - g-track, 12,7 mm (0,5 in) wide magnetic tape for information interchange using NRZI at 32 ftpmm (800 ftpi) - 32 cpmm (800 cpi) Traitement de linformation - Bande magnbtique B 9 pistes de 12.7 mm (0,5 in) de large, p
2、our / b) The spacing between the first detected bit and the last detected bit of a row shall be less than IO,8 urn (425 pin); 4.1 Operating environment Tapes used for data interchange shall be operated under the following conditions: c) There shall be a minimum apparent spacing between any bits of s
3、uccessive rows of 11,2 urn PI40 pin). 5.5 Static skew - temperature: 16 OC to 32 OC (60 OF to 90 OF); - relative humidity: 20 % to 80 %; - wet bulb temperature: not greater than 25 “C (78 OFI. Conditioning before operating: If a tape has been exposed during storage and/or transportation to condition
4、s outside the above values, it should be conditioned for a period of 2 h to 12 h depending upon the extent of exposure. 4.2 Storage and transportation The recommendations for storage and transportation environ- ment are specified in annex C. Responsibility for ensuring that adequate precautions agai
5、nst damage are taken during shipment shall be with the sender (see annex Cl. 4.3 Wind tension For interchange, the tape winding tension shall be between 2,0 N and 3.6 N (7 ozf to 13 ozf). 5 Recording 5.1 Method of recording The “non return to zero change-on-ones recording” (NRZl) method of recording
6、 shall be used where a ONE is represented by a change of direction of longitudinal magnetization. 5.2 Density of recording The nominal density shall be designated by 32 ftpmm (800 ftpi). The actual density shall be 31,5 ftpmm (800 ftpi). The resulting nominal flux transition spacing is 31,75 urn (1
7、250 uin). The static skew shall be less than 3,81 urn (150 pin). This con- dition is required to be satisfied for both flux transition polarities. 5.6 Signal amplitude 5.6.1 Standard Reference Amplitude The Standard Reference Amplitude is the average peak-to-peak signal amplitude derived from the Ma
8、ster Standard Reference Tape on the qualified measurement system at the density of 32 ftpmm BOO ftpi) and the recording current Zr of 2,l x Zf. The signal amplitude shall be averaged over 4 000 flux tran- sitions, and shall be measured on the read-while-write pass. The reference current Zr is the mi
9、nimum current which produces the Reference Field. 5.6.2 Average signal amplitude The average peak-to-peak output signal amplitude of an inter- changed tape at 32 ftpmm (800 ftpi) shall be between 70 % and 115 % of the Standard Reference Amplitude. Averaging shall be done over a minimum of 4 000 flux
10、 tran- sitions which, for the interchange tape, may be segmented into blocks. Averaging shall be done on the first read pass after interchange. 6.6.3 Maximum signal amplitude An interchanged tape shall contain no flux transition the base- to-peak signal amplitude of which exceeds 120 % of one-half t
11、he Standard Reference Amplitude on the first read pass after interchange. 2 ISO/IEC 1863 : 1990 (El 5.6.4 Minimum signal amplitude An interchanged tape shall contain no flux transition the base- to-peak signal amplitude of which is less than 35 % of one-half the Standard Reference Amplitude on the f
12、irst read pass after interchange. 5.7 Erasure 5.7.1 Erase direction When erased, the rim end of the erased area of the tape shall be magnetized so that it is a North-seeking pole and the hub end of the erased area is a South-seeking pole (see annex B). 5.7.2 Erase width The full width of the tape sh
13、all be d.c.-erased in the direction specified in 5.7.1. 5.7.3 Residual signal The tape shall be erased so that any residual signals, including NRZl at 32 ftpmm (800 ftpi) and 356 ftpmm (9 042 ftpi) and phase encoding at 126 ftpmm (3 200 ftpi) are less than 4 % of the Standard Reference Amplitude at
14、32 ftpmm (800 ftpi). 7 Data representation 7.1 Coded representation of characters Characters shall be represented by means of the -I-bit coded character set (see IS0 6461, the 8-bit coded character set (see IS0 4873) or, where required, of an extension of the -/-bit coded character set (see IS0 2022
15、). The bit-to-track allocation shall be as follows: 7.1.1 7-bit coded characters Binary weight 20 2 22 23 24 25 26 - - Bit designation bl bg b3 b4 b5 b6 b, - P Track 121811191315161714 Track 7 shall always be recorded with bit ZERO. Bit P in track 4 shall be the parity bit. The parity shall be odd.
16、7.1.2 8-bit coded characters Binary weight 20 2 22 23 24 25 26 27 - Bit designation bl b2 b3 b4 b5 b6 b7 bg P Track 2 8 1 9 3 5 6 7 4 6 Track configuration Bit P in track 4 shall be the parity bit. The parity shall be odd. 6.1 Number of tracks There shall be nine tracks. 6.2 Track identification Tra
17、cks shall be numbered consecutively beginning at the reference edge with track 1 (see figure 1). 6.3 Track positions The distance from the centrelines of the tracks to the reference edge shall be Track 1 : 0,74 mm (0,029 in) Track 2: 2,13 mm (0,084 in) Track 3: 353 mm (0,139 in) Track 4: 4,93 mm (0,
18、194 in) Track 5: 6,32 mm (0,249 in) Track 6: 7,72 mm (0,304 in) Track 7: 9,12 mm (0,359 in) Track 8: lo,52 mm (0,414 in) Track 9: 11,91 mm (0,469 in) The tolerance shall be f 0,08 mm (0,003 in) for all tracks. 6.4 Track width The width of a written track shall be 169 mm min. (0,043 in min.) 7.2 Repr
19、esentation of binary data When the coding method requires it, the coded representations recorded in data rows shall be regarded as a set of bit positions, each containing a bit, which can be either a ZERO or a ONE. The binary weights, bit designations and track allocation shall be given in 7.1. 8 Fo
20、rmat of the tape 8.1 Block structure All data blocks shall consist of a data portion followed by a Cyclic Redundancy Check character (CRC) and a Longitudinal Redundancy Check character (LRC). 8.2 Length of the data portion The data portion of a data block shall consist of at least 18 characters and
21、at most of 2 048 characters. However, larger blocks may be used by agreement between the interchanging parties. 8.3 Cyclic Redundancy Check character (CRC) The Cyclic Redundancy Check character, CRC, shall be hardware-generated by shifting serially the relevant bits as specified in annex A through a
22、 g-bit shift register described by the generator polynominal x9 + x6 + x5 + x4 + x3 + 1 3 ISO/IEC 1963 : 1990 (E) 8.4 Longitudinal Redundancy Check character (LRCI The Longitudinal Redundancy Check character, LRC, shall have a ONE in all tracks in which the longitudinal count would otherwise be odd,
23、 else a ZERO. 8.5 Gaps 8.5.1 Initial gap Between the hub end of the BOT marker and the first recorded character of the first block there shall be a gap with a length of 76 mm min. (3 in min.) and 7 600 mm max. (300 in max.). It shall be erased in accordance with 5.7. 8.5.2 Interblock gap The length
24、of interblock gaps shall be - 15 mm nom. (0,6 in nom.) - 12,7 mm min. (0,5 in min.) - 7 600 mm max. (300 in max.). This gap shall be erased in accordance with 5.7. The actual gap length depends on the number of consecutive erase instruc- tions. 8.5.3 CRC gap There shall be a gap of 0,127 mm + 0,013
25、mm (0,005 in f 0,006 5 in) between the last recorded data character and the CRC. 8.5.4 LRC gap There shall be a gap of 0,127 mm f 0,013 mm (0,005 in + 0,000 5 in) between the CRC and the LRC characters. 8.6 Tape Mark The Tape Mark shal be a control block comprising - a row with ONES in tracks 2, 3 a
26、nd 8 and erasure in tracks 1, 4, 5, 6, 7 and 9; - a CRC gap; - a CRC character containing only ZEROS; - an LCR gap; - an LCR character. A Tape Mark shall be separated from other blocks by an inter- block gap. The use of Tape Marks is specified in IS0 1001. 9 Quality of recording for data interchange
27、 Tape shall not be used for data interchange where the number of gaps which have been elongated due to erase instructions exceed two in number or 0,5 % of the total number of blocks written, whichever is the larger. No permanent parity errors whilst writing are permissible in the data to be intercha
28、nged. 10 Erasure of ID bursts The use of tapes recorded at 63 cpmm (1 606 cpi) and 246 cpmm (6 250 cpi) for recording at 32 cpmm WO cpi) presents a difficulty in that the identification burst on such a tape extends from a minimum of 43,2 mm (1,7 in) before the trailing edge of the BOT marker. To ensure proper working of the 32 cpmm (800 cpi) system, it is necessary for the burst to be erased, either by the system itself or by bulk erasure. 4
