JPH0528661A - Data reading method - Google Patents

Abstract

PURPOSE:To shorten data reading time by previously reading data of a data block at a immediately preceding position, at least, at the time of processing the restoration of a defective block. CONSTITUTION:An optical disk 17 is provided with a parity block P for restoring data of the defective block at every data group consisting of plural data blocks D1-D24. When a reading instruction is for reading data from D2-D24 except head D1 within the plural continuous data blocks D1-D24 of the data group G, reading is executed by previously reading data from data of the data block in the data group G at the immediately preceding position, at least, in order for restoring data in the data block D2-D24 of the reading instruction. Consequently, there in no need to read the whole data block from the first one so as to attain the high speed of a reading processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data reading method,
More specifically, the present invention relates to a method of reading data stored in each block recorded on a recording medium such as an optical disk.

In recent years, there has been a demand for speeding up of a storage device including a recording medium such as an optical disk provided in a computer. As one of the speed-ups, it is required to speed up the read-out speed of the data recorded on the recording medium.

[0003]

2. Description of the Related Art In recent years, optical disks of high density and high storage capacity have been adopted as storage media in storage devices. In this optical disc, for example, each data block in which 512-byte data is recorded is provided with an error correction code for restoring the data in the block when the data is defective. Furthermore, when one defective data block cannot be restored by the error correction code, the data of the parity block provided in the data group to which this defective data block belongs is used for restoration. That is, the data group is composed of a plurality of blocks (for example, 25 blocks), of which 2
The four blocks are data blocks and the remaining one is a parity block. A value (parity data) obtained by EOR (exclusive OR) all the data of all 24 data blocks belonging to the data group to this parity block provided for each data group in advance Are recorded respectively.

When reading data from the optical disc having the above-described structure, for example, when reading the fourth data block to the seventh data block of a certain data group, the optical head as a read head is sought and the fourth data is read. Starting from the block, the data up to the seventh block is read out successively.

At this time, for example, when the data of the first fourth block is defective and cannot be restored by the error correction code of the same block, all the blocks including the parity block of the data group to which the fourth data block belongs are included. The block data is read from the first (first) block. Then, the data of all blocks (including the parity block) of the data group except the defective fourth data block is EORed (exclusive OR),
The defective data block is restored.

[0006]

By the way, when there is a defective block in the restoration processing, the data of the first data block at the head of the data group is always read from the data of the first data block to the last 25th parity block in the reading order. Each data had to be read. That is, when a defective block occurs, it is necessary to move the optical head to the first data block of the data group to which the defective block belongs and read again from that block. Therefore, if a defective block occurs, it takes a very long time to restore and read the data of the desired block.

The present invention has been made in order to solve the above-mentioned problems, and its purpose is to reduce the amount of movement of the read head in the process of restoring a defective block and to shorten the data read time. It is to provide a reading method.

[0008]

In order to solve the above-mentioned problems, the present invention forms a large number of data groups consisting of a plurality of data blocks provided at consecutive positions, and the data of unreadable blocks is set for each data group. When a predetermined data block is read from a recording medium provided with a parity block for restoring the data block, at least one position before the predetermined data block is read in order to restore the data of the data block of the read command in advance. The data of the data block in is read sequentially.

[0009]

Therefore, according to the present invention, when there is an uncorrectable defective data block in one of the predetermined data blocks, at least one of the predetermined data blocks is to be restored in advance using the parity block of the data group. Since the data of the data block at the previous position is being read,
Only that portion need not be read when performing restoration processing. As a result, it is not necessary to move the read head again to read all the data blocks and redundant blocks of the data group in order to perform the restoration process, and the time required for the restoration process is shortened accordingly, and the read process The speed can be increased.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment embodying the present invention is shown in FIG.
It will be described with reference to FIG. FIG. 1 is a block diagram showing an outline of a data reading device, which is a central processing unit (CPU) 11
Control program memory 13 via system bus 12
Also, the operation memory 14 is connected to the rewritable work memory 14 and operates according to the program stored in the control program memory 13, and the operation result and the like are temporarily stored in the work memory 14. The CPU 11 is connected to the optical disk drive device 15 and the head movement control circuit 16 via the system bus 12. The optical disk drive device 15 rotates the optical disk 17 as a recording medium based on a control signal from the CPU 11.
The head movement control circuit 16 drives and controls an actuator 19 that reciprocates an optical head 18 as a reproducing head based on a control signal of the CPU 11 to move (seek) the optical head 18 to a predetermined read position on the optical disc 17.
A format control circuit 20 is connected to the CPU 11 via a system bus 12, and the format control circuit 20 reproduces, that is, reads the data recorded on the optical disc 17 via the optical head 18 based on a control signal from the CPU 11. .

As shown in FIG. 2, the optical disc 17 has
A large number of consecutive blocks (sectors) are formed on the track T, and 25 consecutive blocks are set as one data group G, of which 24 blocks are data blocks D.
1 to D24, and the following one block is a parity block P for the data group G. Therefore, the data groups G including the parity block P are continuously formed on the track T.

The data blocks D1 to D24 and the parity block P have a storage area of 512 bytes in this embodiment, and each data block D1 to D24 restores the data of the data block in addition to the data portion for recording the data. An ECC unit is provided for recording an error correction code for doing so. Further, the parity block P is EO for all the data of each data block D1 to D24 of the corresponding data group G.
The parity data of the content obtained by R (exclusive OR) is recorded. When one of the data blocks D1 to D24 of the data group G has an unreadable defective data block, the parity data of the parity block P of the data group is used to restore the data of the defective block. You can do it.

Next, the operation of the data reading device configured as described above will be described with reference to the flowchart showing the operation of the CPU 11. For convenience of explanation, a case will be described where the data of the third data block D3 to the fifth data block D5 of the data group shown in FIG. 2 is read.

When a read command for reading the data blocks D3 to D5 recorded on the rotating optical disk 17 is input to the CPU 11, the CPU 11 reads the data blocks D3 to D5.
To the data group G to which D5 belongs, the position of the data group G on the optical disk 17, that is, the optical head 1
A position (reading position) for seeking 8 is obtained (step 1). Then, when the seek position of the optical head 18 is obtained,
The CPU 11 seeks the optical head 18 via the head movement control circuit 16 and the actuator 19 (step 2).

The optical head 18 has data blocks D3 to D5.
C to the position of the data group to which the
The PU 11 starts from the first data block of the data group G to which the data blocks D3 to D5 belong, that is, from the reading of the data block D1 (step 3,
4). When the top data block D1 is read out, the data in that block is read out in step 5 and immediately stored in the working memory 14, and then in step 6 the next data block is the data block based on the read command (hereinafter referred to as "data block"). It is called a target data block). If it is not the target data block, the data of the next data block is read in step 7,
In step 5, the data is stored in the work memory 14. Therefore, the data of the data block D2 is also immediately stored in the working memory 14.

When the data of the data block D2 is also immediately stored in the working memory 14, the first target data block D3 is read next. Therefore, when the CPU 11 reads the data of the data block D3, an error occurs and the data is corrected. Check whether it is impossible (steps 8 to 10).
If there is no error or if the error can be corrected, the data is restored and stored in the working memory 14 (step 11), and it is determined whether the next data block is also the target data block. Then, in the case of the target data block, the data of the next target data block is read out in the same manner as described above, and the operation for presence / absence of an error is performed and stored in the working memory 14 when there is no error. Therefore, the data of the target data blocks D3 to D5 following the target data block D3 are also sequentially stored in the working memory 14 if there is no error. When the data of the target data blocks D3 to D5 are read without error, the CPU 11 ends the reading process.

On the other hand, 1 of the target data blocks D3 to D5
If there is a data error in one of the blocks and the data cannot be restored even using the error collect code of the block, the CPU 11 performs the restoration process of the target data block. That is, as shown in FIG. 4, the data block to be read next is sequentially read, and the data read up to the parity block P at the end of this data group is continued while checking the error correction inability, and the data is read as the working memory. 14 (steps 21 to 25). When the data of the parity block P is read, the CPU 11 checks whether the data of the data blocks D1 and D2 read prior to the target data blocks D3 to D5 is error-correctable (step 26).

When there is no error, the data of the other data block excluding the defective block and the data of the parity block P are exclusive-ORed to restore the data of the defective block. Then, when it is restored, it is assumed that all the target data blocks have been read, and the reading process is terminated (step 2
7, 28).

If there is any other uncorrectable defective data block in the restoration process, the defective target data block cannot be restored, and the read failure processing operation starts.

As described above, in this embodiment, when the data of the target data block based on the read command is read, the data block D1 at the head of the data group to which the target data blocks D3 to D5 belong is read sequentially. If one of the target data blocks D3 to D5 is an uncorrectable defective data block and the restoration process is performed using the parity block P of the data group, the subsequent block data is read out sequentially and the restoration process is performed. The data of the data block and the data of the parity block P are all read. As a result, it is not necessary to read all the data blocks and the parity block P of the data group from the beginning in order to perform the restoration process, the time required for the restoration process is shortened accordingly, and the read process can be speeded up. it can.

The present invention is not limited to the above-described embodiment. For example, in the above-mentioned embodiment, the data block at the head of the data group to which the target data block belongs is read out. If it exists, it may be the data block immediately preceding the target data block. If the optical head 18 seeks the data group and the first data block read at that time is before the target data block, the data reading may be started from the data block.

Further, in the above-described embodiment, the presence or absence of an error, the error correction, etc. are not performed when the data before the target data block which is read in advance is read, but this is performed when it is read. Good.

[0023]

As described in detail above, according to the present invention, there is an excellent effect that the amount of movement of the read head can be reduced and the data read time can be shortened in the process of restoring a defective block.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a data reading device showing an embodiment of the present invention.

FIG. 2 is a diagram showing a data recording state of an optical disc showing an embodiment of the present invention.

FIG. 3 is a flowchart showing the operation of the reading device according to the embodiment of the present invention.

FIG. 4 is a flowchart showing an operation of a restoration process according to an embodiment of the present invention.

[Explanation of symbols]

11 Central Processing Unit (CPU) 13 Control program memory 14 Working memory 15 Optical disk drive 16 Head movement control circuit 17 Optical disc as recording medium 18 Optical head 19 actuators 20 Format control circuit T track G data group D1 to D24 data block P Parity Block

Claims (2)

[Claims] 1. A plurality of data groups each of which is formed of a plurality of data blocks provided at consecutive positions are formed.
For a recording medium provided with a parity block for restoring the data of the defective block for each data group, the read command is issued from the data block excluding the data block at the head position among a plurality of continuous data blocks of the data group. At the time of data reading, in order to restore the data of the data block of the read command in advance, the data of the data block of the data group at least one previous position is sequentially read in order. . 2. Forming a large number of data groups consisting of a plurality of data blocks provided at consecutive positions,
For a recording medium that has a parity block for restoring the defective block data for each data group, the read command is a data block in the middle of all the consecutive data blocks of the data group excluding the data block at the head position. When reading data from, the data read method is characterized in that the data of the data block of the read instruction is read in advance from the data of the data block at the head position of the data group.