JPS6022777A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To reduce less a defective area to prevent the reduction of recording capacity due to a defect of a recording medium by absorbing a constant error produced at a part of a recording area into a gap G to obtain a nondefective sector and at the same time reducing the DATA part of a data field if the absorption of the error is impossible. CONSTITUTION:An ECC error is detected after both the DATA and ECC parts are read, and an ECC correcting circuit 7 is operated to know an error location. Here it is known that the error location exists only at the rear part of the dapa field. Thus it is checked whether the physical positions of both ID and data fields can be altered or not. When this alteration is possible, the physical positions of both fields are altered by the next rotation and recorded. This format to be altered can be fixed or varied in response to the error location. If the alteration is impossible, the relevant sector is decided defective and processed. Otherwise the DATA part is reduced to secure the application of said sector.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an improved method of utilizing a recording area in a magnetic disk device.

(Prior Art) In recent years, as the amount of information handled by information processing systems has increased, the recording density of magnetic disk devices has been increasing. However, the higher the recording density, the more the recorded information deteriorates due to defects in the recording medium, and there is a desire to improve this problem.

FIG. 1 shows one track (cylinder number X, head number y) on a magnetic disk, which is composed of a plurality of sectors. FIG. 2(a) shows the structure of one sector, which consists of a gap part G, an ID field, and a data field. Further, the ID field is composed of a synchronization section 5YNC, an address section ADH, and a check section CRC, and the data field is composed of a synchronization section 5YNC, a data section DATA, and a check section CRC. Also, the address part ADR of the ID field is the flag part FLG as shown in FIG. 2(b).
, a cylinder section CYL indicating the cylinder number, a section HEAD indicating the head number, and a sector section SEC indicating the sector number. If sector 3 in Figure 1 is defective in a magnetic disk device configured in this way, (1)
This track is replaced as a defective track.

(2) Replace only the sector as a bad sector.

In the case of (1) above, effective sectors other than sector 3 are wasted, and the higher the density, the more desirable it is. Further, although the case (2) is far superior to the case (1), further improvement is desired.

In the above, a bad track or bad sector is a permanent error caused by a dropout of the recording medium, etc.
2) Occurs in all ID fields, (3) in part of data fields, (4) in all data fields, etc. However, defects such as dropouts occurring in part of the ID field (particularly the front part) in 1) or dropouts etc. occurring in part of the data field (particularly the rear part) in (3) are ID field and data
It can be absorbed in the gap G in front of the ID field, shifted from the physical position of the field.

In conventional magnetic disk drives, the above-mentioned defects are simply regarded as defects and there is no means for repairing them. In addition, in magnetic disk drives that can correct errors by using ECC (error correction code) instead of CRC in the data field check section, error correction processing must always be performed, and extra time is always required for error correction. I needed it.

(Objective of the Invention) The present invention has been made in view of the above points, and its object is to provide an improved magnetic field that reduces the number of defective areas and reduces the decrease in recording capacity due to defects in the recording medium. The objective is to provide a disk device.

A further object is to provide a magnetic disk drive that reduces the time required to correct permanent errors caused by permanent errors.

(Structure of the Invention) In order to achieve the above object, the present invention corrects permanent errors occurring in a part of the recording area by converting them into ID unyield and data/7.
By shifting the physical position of the 4-field, the sector is made to be a good sector by being absorbed by the gap G, and when it cannot be absorbed, the DATA portion of the data field is reduced.This will be explained in detail below.

(Embodiment) FIG. 3 shows a block diagram of a magnetic disk device related to the present invention. In FIG. 3, reference numeral 1 indicates a magnetic disk control device, and a write data register (WDR) 2.

Switching circuits 3, 4, 5. CRC circuit6. Error correction circuit 7. No9 serial converter (p/s) s
, a serial-parallel converter (S/P) 9, a read data register (RDR) 1o, a read data buffer 11°, and a control unit 12 that controls these.

13 is a magnetic disk.

In the above, the CRC circuit 6 performs CR based on a well-known polynomial.
Perform C check. The error correction circuit 7 is capable of correcting burst errors of a predetermined length.
d Am manufactured by Micro Devices (AMD)
It is Z8065. In the magnetic disk device configured in this way, when writing the data shown in FIG. 4(b) (hereinafter this is called the first format write and abbreviated as F-Wl), the steps shown in FIG. 5(a) to It operates according to the flow in (c). The data to be recorded on the recording medium in the flowcharts of FIGS. 5(a) to (c) is set in the WDR 2, and when the writing is ready, it is sent to the P/S 8, where it is converted into parallel to serial data and magnetically converted. The data is transferred to the disk 13. As data for writing, first, a predetermined number of (1) Gear Tsubu G month data, (2) 5YNC data, (3)
Oborozuki data, (4) C output from CRC circuit 6
RC data, (5) gap fG data, (6)
Data for 5YNC.

(7) DATA and (8) ECC data output from the error correction circuit 7 are transferred in this order. In the above, the CRC data in (4) is requested by giving the ADR data to the CRC circuit 6, and the ECC data in (8) is found by giving the DATA in (7) to the error correction circuit 7. .

When reading the data recorded above (A
Transferring the DR section and DATA section to the higher-level device is called ``format read uF-R'', and transferring only the DATIA section to the higher-level device is called ``READ'').6.
It operates according to the flows shown in Figures (a) and (b).

FIG. 6 takes the above-mentioned READ operation as an example, and in the FR, ADR data and DATA part data of the sectors are sequentially read from the II OII sector and transferred to the host device. Magnetic disk 1 according to the flow shown in Fig. 6 (a) j (b)
The read data transferred from S/'P 9 is serial-parallel converted, and after a predetermined number of data are accumulated, R
Set to DR10. The read data set in the RDR 10 is subjected to error determination by the control unit 12 or transferred to the RBII, and further necessary data is transferred to the error correction circuit 7.

Now, when attempting to read recorded data in a certain sector, the control section 12 enters the sector pulse signal monitoring state shown in FIG. 4(a). When a sector pulse is detected in this state, the control unit 12 sequentially reads the output of RDR1θ. 5YN here
When the C data is detected, the data in the ADR section is read and transferred to the control section 12, and the data is also input to the CRC circuit 6 via the switching circuit 3. When the ADR section is completely read, the transfer to the control section 12 is stopped, and the CRC data is continuously input to the CRC circuit 6. Once all the CRC data has been read, the input to the CRC circuit 6 is completed and a check is made to see if a CRC error has occurred. If a CRC error has occurred, it is determined that there is a media defect due to dropouts or an abnormality in the read data due to noise, etc. Assuming that there is, error handling is performed. On the other hand, if it is determined that no CRC error has occurred, the control unit 12 checks whether the read ADR data and the target address match, and if they do not match, it does not perform the data field reading operation and continues. wait for sector pulse. On the other hand, if they match, the data field reading operation will be affected.5.
When the YNC data detection operation is performed and the 5YNC data is detected, the DATA section is read. The data read from the DATA portion is sequentially transferred from the RDR 1o to the RB 11 and is also input to the error correction circuit 7 via the switching circuit 4. When all of the DATA section is read, the transfer to the RBII is completed, and the ECC section data is subsequently input into the error correction circuit 7.

Once the ECC section data is read, the input to the error correction circuit 7 is completed, and the state of the ER terminal of the error correction circuit 7 is checked to see if the data input to the error correction circuit 7 is normal. If there is an abnormality here, it is assumed that there is a medium defect due to dropout or the like or an abnormality in the read data due to noise or the like, and error processing is performed. This error processing usually operates the control terminal of the error correction circuit 7 to check whether the error can be corrected. If the error can be corrected, the error location is checked and the read data in the RBII and the correction data output to the D terminal are combined. Correct the data by taking the exclusive OR of

On the other hand, if it cannot be corrected, it is determined that a burst error of a predetermined length or longer has occurred, and necessary processing is performed. In general, defects in recording media are found at the time of shipment of the medium, or This can be known by repeatedly performing READ and not being able to read normally even after a predetermined number of attempts.

Next, the operation for repairing a permanent error caused by a media defect when the defect location is known will be explained. According to the present invention, the F
-W Write in a format different from 1 F-
A suitable result can be obtained by newly adding the instruction W2. Now, if a medium defect is known, for example, in sector 3 in FIG. 1, or if it is found, each sector is sequentially accessed until sector 3 is found. When sector 3 is found, the data field is read. Here, if the 5YNC portion of the data field cannot be detected, a predetermined number of attempts are made, and if it still cannot be detected, it is treated as a bad sector. On the other hand, if the 5YNC part can be detected, continue with DAT.
Read part A and ECC part. When the DATA section and the ECC section are read and an FCC error is detected, the FCC correction circuit 7 is operated to know the error location. If it is found that the error location is only at the end of the data field, check whether the physical location of the ID field and data field can be changed (i.e., the gap G
If it is determined that it can be changed (whether it can be absorbed or not), then in the next rotation the physical positions of the ID field and data field are changed and recorded as shown in Figure 4(c).The changed format is fixed. or it may be variable depending on the error location.If it is found that it cannot be changed in the above, the sector is treated as a bad sector, or
Alternatively, as will be described later, the DATA section is reduced so that the sector can be used.

In addition, in the above case, if the error correction circuit 7 finds that it cannot be corrected (there is a burst error of a predetermined length or more), D
The ATA section is reduced and formatted and written. If this is repeated and the ECC error disappears or a correctable sheller location is found, the physical positions of the ID field and data field can be changed as described above if possible based on the length of the DATA length at that time. On the other hand, if the sector cannot be changed, it is treated as a bad sector as described above, or the DATA section is reduced so that it can be used. Next, to reduce the DATA section and use that sector, the fourth step is
As shown in FIG. There is an advantage that the spare sectors that have been removed are combined and the bad sector can be used effectively.Also, as described above, the reduced sector in the DATA section can be handled in the same way as a normal sector without being used as a spare sector. It is also possible to make the total length of the DATA section of one track variable.

In the above explanation, the CRC was used as the check code for the ID field part, but by using the FCC instead of the CRC, the error location can be detected in the same way as above.D
It is also possible to record and reduce the DATA section by shifting the physical positions of the fields and data fields in the opposite direction to the above.

(Effects of the Invention) As described in detail above, according to the present invention, the error location is known and the physical positions of the pID field and the data field are shifted and recorded, or the DATA field is reduced and recorded. This has the advantage of reducing the probability of a bad sector and allowing effective use of the recording area.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the track configuration of a magnetic disk device, FIG. 2 is a diagram showing a sector format, FIG. 3 is a block diagram of the magnetic disk device, and FIGS. 4(a) to (e) are diagrams according to the present invention. A diagram explaining the sector former, Fig. 5(a)
- (c) is a flowchart diagram of FW, Fig. 6 (a)
, (b) is a flowchart diagram of READ. DESCRIPTION OF SYMBOLS 1... Magnetic disk control device, 3,4.5... Switching circuit, 6... CRC circuit, 7... Error correction circuit,
13...Magnetic disk. Patent Applicant: Oki Electric Industry Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4 Figure 6 (0)

Claims (1)

[Claims] In a magnetic disk device that divides a track into multiple sectors and records fixed length data in the sectors or reads data from the sectors, when a permanent error occurs in the sector, the error location of the sector is known. If the location is a position where the physical positions of the ID field and data field can be shifted to make it a normal sector without permanent errors, then the physical position of the ID field and data field is shifted and the position can be made a normal sector, and on the other hand, it is a position that cannot be made a normal sector. A magnetic disk device characterized in that it has a function of reducing a DATA section and using it as a spare sector.