This standard specifies the quality of recorded signals, track configuration and track format for 130 mm floppy disks with a bit density of 13262 flux turns/radian for data exchange between data processing systems. GB/T 15131.3-1995 Information processing data exchange 130 mm modified frequency modulation floppy disks with a bit density of 13262 flux turns/radian and 80 tracks per side Part 3: Track format B (for 80 tracks) GB/T15131.3-1995 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China Information processing-Data interchange on 130 mm flexible disk cartridges using modified frequency modulation recordingat 13262 ftprad, on 80 tracks on each side Part 3: Track format B for 80 tracks tracksGB/T15131.3—1995
ISO8630/3—1987
This standard is equivalent to the international standard ISO8630/3--1987 "130mm (5.25in) floppy disks with a bit density of 13262 flux turns/radian and 80 tracks per side recorded by the modified frequency modulation system for information processing data exchange Part 3: Track format B (for 80 tracks)".
0 Introduction
GB/T15131 specifies the performance of 130mm floppy disks with a bit density of 13262 flux turns/radian and 80 tracks per side recorded by the modified frequency modulation system (MFM).
GB/T15131.1 specifies the size, physical properties and magnetic properties of floppy disks. This provides the possibility of practical exchange between data processing systems.
GB/T15131.2 specifies another track format for data exchange. GB/T15131.1 and GB/T15131.3 provide the conditions for all data exchanges between data processing systems with the labeling system specified in GB/T13703.
1 Subject matter and scope of application
This standard specifies the quality of recorded signals, track configuration and track format for 130mm floppy disks with a bit density of 13262 flux reversals/radian used for data exchange between data processing systems. 2 Conformity
When a floppy disk meets all the requirements of the first and third parts of GB/T15131, the floppy disk is consistent with GB/T15131. 3 Reference standards
GB1988 Information processing Seven-bit coded character set for information exchange GB2311 Information processing Seven-bit and eight-bit coded character set code expansion technology GB11383! Information processing - Eight-bit code structure and encoding rules for information exchange GB/T15131.1 Information processing - 130 mm floppy disks with a recording bit density of 13262 flux turns/radian and 80 tracks per side using the modified frequency modulation system for data exchange - Part 1: Dimensions, physical properties and magnetic properties Approved by the State Administration of Technical Supervision on April 5, 1995 and implemented on December 1, 1995
GB/T 15131.3—1995
GB/T15131.2 Information processing - 130 mm floppy disks with a recording bit density of 13262 flux turns/radian and 80 tracks per side using the modified frequency modulation system for data exchange - Part 2: Track format A (for 77 tracks) GB/T13703 Information processing, floppy disk volume and file structure for information exchange 4 General requirements
4.1 Recording method
The recording method is modified frequency modulation (MFM). The conditions are: a. Write a flux flip at the center of each bit cell containing "1", b. Write a flux flip at each cell boundary between consecutive bit cells containing "0". The provisions in Article 4.12 are exceptions.
4.2 Track position tolerance of recorded floppy disks Under the entire use environment conditions specified in GB/T15131.1, the center line of the recorded track should be within ±0.0425mm of the nominal position.
4.3 Recording deviation angle
At the moment of writing or reading a flux flip, the flux flip may have an angle of 0°±18° with the radial direction. Note: Since the track may be written or rewritten at the tolerance limit values ​​given in Articles 4.2 and 4.3, part of the original information may be left on one side of the newly written data, causing unwanted noise when reading. Therefore, it is necessary to use the write-after-erase method to trim the track edge. 4.4 Recording density
4.4.1 The nominal recording density is 13262 flux reversals/arc arc. The nominal bit unit length is 75.5urad. 4.4.2 The average bit unit length of the long item shall be the average of the bit unit lengths measured over the entire sector. It shall be within ±3.0% of the nominal bit unit length.
4.4.3 The average bit unit length of the short item (relative to a specific bit unit) shall be the average of the lengths of the preceding 8 bit units. It shall be within ±8% of the average bit unit length of the long item. 4.5 Flux reversal spacing (see Figure 1)
130%~165%
185%225%
The instantaneous distance between flux reversals is affected by the read and write processes, the order of recorded bits (pulse crowding effect) and other factors. The position of the flip is defined as the position of the signal peak during readout. The test is performed using a bee-value sense amplifier. See Appendix B (reference) and Appendix C (reference.
4.5.1 The spacing between consecutive "1" flux flips should be 80% to 120% of the short-term average bit unit length. 4.5.2 The spacing between the flux flip between two "0"s and the preceding \1" or the following "1" flux flip should be 130% to 165% of the short-term average bit unit length.
4.5.3 When there is only one \0" between two "1", the spacing between the two "1\ flux flips should be 185% to 225% of the short-term average bit unit length.
4.6 Average signal amplitude
GB /T15131.3—1995
The average signal amplitude on any track on each side of a floppy disk for data exchange (see GB/T15131.1) should be less than 160% of the standard reference amplitude SRAr of 1f and greater than 40% of the standard reference amplitude SRAz of 2f. 4.7 Byte
A byte is a combination of 8-bit positions, identified by B1 to B8, and the bit at each position should be "0" or "1". 4.8 Sector
All tracks are divided into 15 sectors of 512 bytes. 4.9 Cylinder
A pair of tracks with the same track number (there is one track on each side of the disk). 4.10 Cylinder serial number
The cylinder number is represented by two digits, which is the same as the track serial number of the track on the cylinder. 4.11—Data capacity of a track
The data capacity of a track is 7680 bytes. 4.12 Hexadecimal notation
The following bytes are represented in hexadecimal notation: (00) represents (B8～B1) = 00000000
(01) represents (B8～B1) = 00000001
(02) represents (B8～B1) = 00000010
(4E) represents (B8～B1) 01001110
(FE) represents (B8～B1) = 11111110
(FB) represents (B8~~B1) = 11111011
(A1)* represents (B8～B1) = 10100001
Among them, there is no boundary flip between B3 and B4. 4.13 Error Check Character (EDC)
Two EDC bytes are generated by hardware, i.e., by serially shifting the relevant bits (see the following definition of each part of the track) through a 16-bit shift register [see Appendix A (reference)]. Its generating polynomial is: X16 +X12 + X5 + 1
5 Track Configuration
After formatting, each track should have 15 usable sectors. The track configuration of each track is shown in Figure 2. Index Gap
5.1 Index Gap
Identifier
Identifier Gap
1st Sector
Data Block
Data Block
Data Block
15th Sector
Avoidance Gap
At nominal recording density, this field shall be no less than 32 bytes but no more than 146 bytes. There are no other requirements except that its content shall not include (A1)* bytes. 453
GB/T15131.3-1995
Writing the index gap begins when the index window is detected. Due to subsequent rewriting, any of the first 16 bytes may be uncertain5.2 Sector Identifier
This field is shown in Table 1.
Identifier Tag
3 bytes
12 bytes
5.2.1 Identifier Tag
This field includes 16 bytes:
12 (00) bytes;
3 (A1)\ bytes;
1 (FE) byte.
5.2.2 Address Identifier
This field includes 6 bytes.
5.2.2.1 Track Address
This field consists of 2 bytes:
Cylinder Address (C)
1 byte
Track Address
1 byte
1 byte
(00) or (01)
1 byte
1 byte
2 bytes
This field represents the cylinder number in binary notation, which is numbered sequentially from the outermost cylinder 00 to the innermost cylinder 79. b. Plane Number (Plane)
This field represents the disk plane. On plane 0, the plane number is (00) on all tracks. On plane 1, the plane number is (01) on all tracks.
5.2.2.2 Sector Number (S)
The first byte represents the sector number in binary notation, from 01 for the first sector to 15 for the last sector. The sectors may be recorded in any order of the sector numbers. 5.2.2.3 Fourth Byte
The fourth byte is always a (02) byte. 5.2.2.4 EDC
These two bytes shall be generated as specified in 4.13 using the sector identifier bytes starting from the first (A1)\ byte of the identifier marker (see 5.2.1) and ending with the fourth byte of the address identifier (see 5.2.2.3). If the EDC is incorrect, the sector is a defective sector. GB/T 13703 specifies the handling of defective sectors. 5.3 Identifier Gap
This field consists of 22 initially recorded (4E) bytes. These bytes may become indeterminate due to overwriting. 5.4 Data Block
This field is shown in Table 2.
12 bytes
5.4.1 Data Tag
3 bytes
This field includes 16 bytes:
12 (00) bytes;
3 A1)* bytes;www.bzxz.net
1 (FB) byte.
5.4.2 Data Field
GB/T 15131.3--1995
1 byte
Data Field
512 bytes
2 bytes
This field includes 512 bytes. If the number of bytes is less than the specified number of bytes, the remaining part is padded with (00) bytes. 5.4.3 EDC
These two bytes shall be generated according to the provisions of 4.13 using the data block bytes starting from the first (A1)* byte of the data marker (see 5.4.1) and ending with the last byte of the data field (see 5.4.2). If the EDC is incorrect, the sector is a defective sector. GB/T13703 specifies the handling method of defective sectors. 5.5 Data Block Gap
This field includes 84 initially recorded (4E) bytes. Due to overwriting, these bytes may become uncertain. It is recorded after each data block and before the next sector identifier. The data block gap after the last data block is located before the track gap.
5.6 Track Gap
This field shall be immediately after the data block gap of the last sector. Write (4E) bytes until the index hole is detected, unless the index window is detected when the last data block gap is written, in which case there shall be no track gap. 6 Data encoding representation
6.1 Standard
The content of the data field should be recorded and interpreted according to the relevant national standard for information coding, for example, GB1988, GB2311 or GB11383.
6.2 Coding method
6.2.1 When required by the coding method, the data field should be regarded as an ordered sequence of eight-bit bytes. In each byte, the position of the bit is identified by B8 to B1. The high bit is recorded at the B8 position and the low bit is recorded at the B1 position. The recording order should be the high bit first.
When the data is encoded according to the eight-bit code, the bit weight of the binary bit is shown in Table 3. When data is encoded according to the seven-bit code, bit position B8 is *0". Data should be encoded in positions B7~~B1 and use the same bit weights as shown in Table 3.
6.2.2 When required by the encoding method, the data field should be regarded as an ordered sequence of binary bit positions, each position containing binary bits.
Bit position
GB/T 15131.3—1995
Appendix A
EDC Execution process
(reference)
Figure A1 is a feedback connection block diagram of the shift register that can be used to generate the EDC byte. Before operation, all bits of the shift register are set to "1". Add the input data to the stored value of C15 of the register (XOR) to form feedback. This feedback signal is added (XOR) to the stored values ​​of C. and Cn in turn. During shifting, the output of the XOR gate is sent to C., Cs, and C12 respectively. When the last data bit is added, the register is shifted again according to the above regulations.
At this time, the register stores the EDC byte.
If the register is still shifting when the EDC byte is written, the XOR operation is prohibited by the control signal. In order to detect whether there is an error when reading, the data bits should be added to the shift register in the same way as when writing. After the data is input, the EDC byte is also sent to the shift register as data. After the last shift, as long as the record is correct, the stored value of the shift register will be all "o\.
Input and Output
(Write EDC)
Appendix B
Procedure and Equipment for Measuring Flux Reversal Spacing (Reference)
B1 General
This appendix specifies the procedure and equipment for measuring flux reversal spacing on a 130 mm double-sided floppy disk recorded in the modified frequency modulation system with a density of 13262 flux reversals/radian.
B2 Format
The disk under test should be written by a disk drive for data exchange. The test is performed on tracks 00 and 76 on both sides. The test pattern codes 11011011 (DB) and 11011100 (DC) are written repeatedly on all test tracks. B3 Test Equipment
B3.1 Disk Drive
The average rotation speed of the disk drive during the entire rotation should be 360 ​​± 3 r/min. The average angular velocity within 32 us should not exceed 0.5% of the average angular velocity during the entire rotation. B3.2 Head
B3.2.1 Resolution
GB/T 15131.3—1995
When using a reference floppy disk (RM8630) with known correction coefficients and a specified test recording current, the absolute resolution of the head on track 76 on side 0 and track 68 on side 1 should be 55% to 65%. The resonant frequency of the head should not be lower than 500,000 Hz. The resolution cannot be changed by changing the head load impedance. The resolution should be measured at the output of the amplifier specified in B3.3.1. B3.2.2 Deviation Angle
In the drive under test, the head is allowed to have a gap deviation angle of 0°±6' in the radial direction of the disk. B3.2.3 Contact
During the media test, the head and the media should be in good contact. B3.3, Reading Circuit
B3.3.1 Reading Amplifier
The reading amplifier shall have a flat response curve of no more than ±1 dB in the frequency band from 1000 Hz to 375000 Hz, and shall not experience amplitude saturation.
B3.3.2 Peak Reading Amplifier
Peak reading is measured using a differential and limiting amplifier. B3.4 Equipment for measuring time intervals
The time interval counter can measure time intervals from 2us to a minimum of 5ns. It can be measured using a pulse oscilloscope.
B4 Measurement Procedure
B4.1 Measurement of Track Reversal Spacing
The flux reversal position shall be measured at the peak of the signal readout. The flux reversal spacing shall be measured by the pulse time interval measured by the read channel amplifier specified in B3.3. B4.2 The flux reversal spacing of all tracks
The time interval t to ts is measured as shown in Figure B1. DB
Article 4.5.1 corresponds to 1 and t2; Article 4.5.2 corresponds to t and t4; 4.5.3 corresponding ts Appendix C
Data separator for MFM recording method decoding
(reference)
C1 On track 00 on the 0th side, the dual-frequency system is represented by a nominal flux reversal period, which is: t represents a \1" bit;
2t represents a \0" bit.
Where: t=2 μs
GB/T15131.3—1995
The data separator should be able to distinguish a time difference of 2us. It can be successfully implemented using a digital data separator or a fixed timer. C2 On all other tracks, the nominal flux reversal spacing given by the improved frequency modulation (MFM) recording method is: t represents a pattern code 11 or 000;
3t/2 represents a pattern code 10 or 01;
2t represents a pattern code 101.
The data separator should be able to distinguish a time difference of 1us. To achieve this and ensure a low error rate, the data separator cannot work in a fixed cycle, but should be able to change with the length of the bit unit. Dynamic data separation can be achieved through various technical means. The most mature method at present is to construct an analog data separator based on a phase-locked oscillator, which can meet the necessary reliability. Additional notes:
This standard is proposed by the Ministry of Electronics Industry of the People's Republic of China. This standard is under the jurisdiction of the Standardization Institute of the Ministry of Electronics Industry. This standard was drafted by the Taiyuan Magnetic Recording Technology Institute of the Ministry of Electronics Industry and the Standardization Institute of the Ministry of Electronics Industry. The main drafters of this standard are Li Jian, Zheng Hongren, Li Guixin, Dong Chengju, and Wang Dalan. 458
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