Method for managing information concerning defects on storage media

Abstract: A magneto-optic storage media is provided with two defect information blocks (21a, 21b) storing information concerning a defect. At the time of reproduction, both the blocks are read (step S1), and it is determined whether or not reading is normal (step S2, S7). If the reading of both the blocks are normal, it is determined which of the respective numbers of registrations of the information concerning a defect in both the blocks is larger (step S25), so that the block in which the number of registrations is larger is employed (step S26, S27). Then, the defect information in the block which was not employed is updated and registered (step S32, S33). If the defect information is not registered, the block is switched (step S28), so that an updating and registering operation is executed again.

Description: The present invention relates generally to a defect information managing method, and more particularly, to a defect information managing method for protecting and managing information concerning a defect which exists on a storage medium. The invention also relates to a device for recording and reproducing data on such a storage medium. Fig. 1 is an illustration showing a track structure of a storage medium applied to a storage device which is background art in relation to the present invention. In Fig. 1, a storage medium is provided with a defect information block 11, an alternate area 12, a user area 13 and the like in the order, for example, from an inside track to an outside track. Information concerning a defect of the storage medium is stored in each track of the defect information block 11. The information concerning a defect includes, for example, information indicating which track is defective. A defective portion of the user area 13 is replaced with the alternate area 12, in which information in the defective portion is stored. In the storage medium 10, the defective portion of the track in the user area 13 is replaced with the alternate area 12 based on the information stored in the defect information block 11, so that the reliability is improved. Meanwhile, if and when digital information is written into a magnetic disk such as a hard disk or a floppy disk, the information is stored with magnetisation being completely inverted corresponding to binary information, so that new information can be overwritten on old information without erasing the old information. However, in the case of a magneto-optic disk, the old information must be erased once before writing. Therefore, in the magneto-optic disk, if an accident such as instantaneous power failure occurs when the information concerning a defect in the above described defect information block 11 is updated, the information on the disk is destroyed. Thus, in the worst case, the entire system cannot be returned. In addition, if the information concerning a defect has been erased, it is liable to be erroneously recognised that no information concerning a defect is registered. IBM Technical Disclosure Bulletin, Vol. 26, No. 10B, March 1984 reflecting the preambles of the independent claims discloses, at pages 5769-5770, the provision on a magnetic disk of a "defective sector map" which stores disk defect information, and a second such map which is an exact duplicate of the first, and so provides a back-up for data recovery should the original map become defective. EP-A-0 272 029 (which constitutes part of the state of the art for the designated countries DE and FR by virtue of Article 54(3) EPC), discloses the provision on an optical disk of localised groupings ("blocks") of data sectors, alternate sectors and mapping sectors. Two mapping sectors are provided in each block, so that the data read from the second mapping sector can be used if the first sector data includes an error. An object of the present invention is to protect information concerning a defect which exists on a storage medium if an accident occurs when the information is updated and registered again. Briefly stated, according to the present invention, first and second defect information storage areas in which information concerning a defect of the storage medium can be stored are provided on the storage medium, a selected one of the first and second areas on the storage medium being updated when the defect information is updated. In accordance with a first aspect of the invention, there is provided a method for a managing defect information stored on a data storage medium (20), said defect information relation to one or more defective portions of the data storage area (22, 23) of said medium and being stored in first and second storage areas (21a, 21b) of the medium, characterised in that, in the process of recording or reproducing data on the storage medium, only defect information in a selected one of said first and second storage areas is used and, in the process of up-dating the stored defect information, the up-dated defect information is stored only in the one of said first and second storage areas not so selected. In accordance with a second aspect of the invention, there is provided a device for recording and reproducing data on a data storage medium, the device being capable of managing defect information by the method of the first aspect of the invention. In the method of the first aspect, the area to be updated may be an area other than an area in which the newest information is stored. The area to be updated may be an area in which the number of registrations of defect information is smaller. According to the present invention, either one of the first and second defect information storage areas on the storage medium is updated. Thus, even if an accident occurs during updating, the information concerning a defect always remains in either one of the defect information storage areas, never to disappear. The present invention will become more apparent from the following detailed description of preferred embodiments, taken in conjunction with the accompanying drawings, in which: Fig. 1 is an illustration showing a track structure of a storage medium applied to a storage device which is background art in relation to the present invention; Fig. 2 is a schematic block diagram showing an electrical structure of a magneto-optical type storage device according to one embodiment of the present invention; Fig. 3 is an illustration showing a track structure of a magneto-optic storage medium according to one embodiment of the present invention; and Figs 4A to 4C are flowcharts for explaining an operation according to one embodiment of the present invention. Fig. 2 is a schematic block diagram showing an electrical structure of a magneto-optical type storage device according to one embodiment of the present invention. In Fig. 2, a memory 2, a recording portion 3 and a reproducing portion 4 are connected to a CPU (Central Processing Unit) 1. The memory 2 comprises a ROM (Read-Only Memory) storing an operation program of the CPU 1 based on flowcharts of Figs. 4A to 4C as described below, and a RAM (Random Access Memory) having a work area. The recording portion 3 is used for writing information into a magneto-optic disk, and the reproducing portion 4 is used for reading the information recorded on the magneto-optic disk. Fig. 3 is an illustration showing a track structure of a magneto-optic storage medium according to one embodiment of the present invention. In Fig. 3, a magneto-optic storage medium 20 is provided with a defect information block 21, an alternate area 22, a user area 23 and the like in the order, for example, from an inside track to an outside track. The alternate area 22 and the user area 23 are the same as those shown in Fig. 1 and so description thereof is omitted. The defect information block 21 is divided into an A block 21a and a B block 21b. Information concerning a defect comprises, for example, a track number of a defective track in the user area 23 and the number of registrations (or the number of times of registration) of the information concerning a defect. When the defect information block 21 is updated or registered again, the A block 21a and the B block 21b are alternately reloaded so that information always remains in one of the blocks even if information in the other block is erased before writing. Therefore, even if an accident such as instantaneous power failure occurs during updating, information before the accident remains. Thus, if and when the system is automatically returned or returned by, for example, turning on again the power supply, the worst situation can be prevented in which the system is down by an impossibility to reproduce defect information and a malfunction is caused by erroneous recognition of the defect information. Figs. 4A to 4C are flowcharts for explaining an operation according to one embodiment of the present invention, where Figs. 4A and 4B show a reproducing operation and Fig. 4C shows a registering operation. Description is made first of the reproducing operation. In the step S1 (referred to as S1 in the figure), the A block 21a and the B block 21b in the defect information block 21 in the storage medium 20 are read. Subsequently, in the step S2, it is determined whether or not reading of the A block 21a is normal. If the reading is not normal, it is then determined in the step S3 whether or not the A block 21a is blank. If the reading of the A block 21a is normal, an A block reading flag is set to a sign indicating that reading is normal, in the step S4. If the A block 21a is blank, the flag is set to a sign indicating that the A block is blank, in the step S5. On the other hand, if the reading is abnormal, the flag is set to a sign indicating that reading is abnormal, in the step S6. Subsequently, in the step S7, it is determined whether or not reading of the B block 21b is normal. If the reading is not normal, it is then determined in the step S8 whether or not the B block 21b is blank. If the reading of the B block 21b is normal, a B block reading flag is set to a sign indicating that reading is normal, in the step S9. If the B block 21b is blank, the flag is set to a sign indicating that the B block is blank, in the step S10. On the other hand, if the reading is abnormal, the flag is set to a sign indicating that reading is abnormal, in the step S11. Then, in the steps S12 to S17, a block to be used when defect information is registered, i.e. a block holding the stored content, is determined based on the above described A block reading flag and B block reading flag. If both the A block 21a and the B block 21b are blank, the defect information does not exist. Thus, in the step S18, a defect flag is reset. Subsequently, in the step S19, the B block 21b is employed. Certainly, the A block 21a may be employed. If the reading of the A block 21a is normal and the B block 21b is blank, the A block 21a is employed, in the step S20. If the A block 21a is blank and the reading of the B block 21b is normal, the B block 21b is employed, in the step S21. If the reading of the A block 21a is normal and the reading of the B block 21b is abnormal, the A block 21a is employed, in the step S22. If the reading of the A block 21a is abnormal and the reading of the B block 21b is normal, the B block 21b is employed, in the step S23. If the reading of both the A block 21a and the B block 21b are normal, the number of registrations of the information concerning a defect stored in each block is stored in a register in the step S24, and the respective numbers of registrations are compared with each other in the step S25. If the number of registrations in the A block 21a is the number of registrations in the B block 21b or more, the A block 21a is employed in the step S26; otherwise the B block 21b would be employed in the step S27. In cases other than the above described cases, a defect information reading error flag indicating that reading of information concerning a defect is abnormal is set in the step S28. Description is now made on a registering operation of the defect information block. When information concerning a defect must be updated and registered again, the block other than the block employed in the above described reproducing operation is updated and registered. First, in the step S31, it is determined whether or not the A block 21a is employed. If the A block 21a is employed, the new number of registrations is added to the number of registrations of the information concerning a defect stored in the A block 21a, to be registered in the B block 21b, in the step S32. On the other hand, if the B block 21b is employed, the new number of registrations is added to the number of registrations of the information concerning a defect stored in the B block 21b, to be registered in the A block 21a, in the step S33. Subsequently, in the step S34, it is determined whether or not registration is normally terminated. If the registration is normally terminated, the operation is terminated. On the other hand, if the registration is not normally terminated, it is determined in the step S35 whether or not the registering operation is executed again. At this time point of determination, if one of the blocks has not been reloaded yet, the block is reloaded. More specifically, re-execution of the registering operation is set in the step S37, and the employed block is switched so that the block is reloaded in the step S38. Considering a case in which both the blocks are reloaded, if both the blocks are in error, a registration error flag is set in the step S36 in order to inform the fact, so that the operation is terminated. Meanwhile, in the above described registering operation, if both the A block 21a and the B block 21b are blank at the time of reproduction and no defect information exists, a defect flag is reset. Thus, the registering operation is not performed. In the above described manner, if and when the defect information block 21 shown in Fig. 3 is registered again or updated and registered, both the blocks are read and either one of the blocks is updated and registered and then, the block is switched so that the remaining block is reloaded. Thus, even if the content of the block to be registered is erased during registration, the content of the other block remains, so that the stored content is held.

Claims: A method for managing defect information stored on a data storage medium (20), said defect information relating to one or more defective portions of the data storage area (22, 23) of said medium and being stored in first and second storage areas (21a, 21b) of the medium, characterised in that, in the process of recording or reproducing data on the storage medium (20), only defect information in a selected one of said first and second storage areas (21a, 21b) is used and, in the process of up-dating the stored defect information, the up-dated defect information is stored only in the one of said first and second storage areas (21a, 21b) not so selected. A method for managing defect information according to claim 1, wherein the one of the first and second storage areas (21a, 21b) to be updated is an area other than an area in which the newest defect information is stored. A method for managing defect information according to claim 1, wherein the numbers of registrations of defect information are respectively stored in said first and second storage areas (21a, 21b), the respective numbers of registrations in said areas are compared with each other, and the storage area having the smaller number of registrations is updated. A method for managing defect information according to claim 1, comprising, in the recording or reproducing process, the steps of determining, for each of said first and second storage areas (21a, 21b), whether the storage area stores no defect information, normal defect information or abnormal defect information, and selecting a said one of the first and second storage areas which stores normal defect information. A method for managing defect information according to claim 4, wherein, in the case that both said first and second storage areas (21a, 21b) store normal defect information, the storage area which stores the greater number of defect registrations is selected. A method for managing defect information according to claim 5, wherein the storage area (21a, 21b) selected in the recording or reproducing process stores the newest defect information. A method for managing defect information according to any one of the preceding claims, wherein the process of up-dating the stored defect information comprises the steps of reading the defect information stored in the storage area (21a, 21b) selected in the recording or reproduction process and storing the read defect information together with any new defect information in the storage area not selected in the recording or reproducing process. A method for managing defect information according to any one of the preceding claims, wherein, after up-dating, in the absence of corruption to the stored defect information, the storage area (21a, 21b) which stores the up-dated defect information is selected for use in the recording or reproducing process. A device for recording and reproducing data on a data storage medium (20) having first and second storage areas (21a, 21b) on which is stored defect information relating to one or more defective portions of the data storage area (22, 23) of said medium (20), the device being capable of managing said defect information by the method of any one of claims 1 to 8. A device according to claim 9, which is capable of recording and reproducing data on a magneto-optic disk as said data storage medium (20).

Inventors: HORIE NOBUYUKI MIKASARYO, MAEDA SHIGEMI, YAMANAKA TOSHIHIRO, HORIE, NOBUYUKI, MIKASARYO, MAEDA, SHIGEMI, YAMANAKA, TOSHIHIRO
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1988
Main classification: G11B20
IPC codes: G11B20