JPH0145646B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a disk data read control method, and specifically to a method for forcedly reading data when a disk is down.

[Conventional technology]

With the rapid development of information processing systems, the importance of the file system that forms the core of the system, especially the magnetic disk device that represents the central position, is increasing.

In a magnetic disk device, the operation of writing or reading information to or from a medium is normally performed through the following steps.

(1) Head positioning (seek) (2) Record collation (search) (3) Information transfer (read/write) The magnetic disk device that performs these series of operations functionally consists of the following elements. has been done.

Namely, a disk drive mechanism that drives and stops the magnetic disk, an access mechanism that moves the head and positions it on a desired track, and a read/write mechanism that writes information on or reads information from the magnetic disk (media). It also consists of a mechanism that controls the traffic between the computer main body and a plurality of media, collates records, and controls the recording and reproduction of information.

By the way, when information is written to a magnetic disk, check information is added to it, and when information is read out, the read information is checked for errors.

Normally, cyclic check (CRC)
Redundancy Check) is used. Further, the sector information on the magnetic disk is as shown in FIG.

FIG. 3 is a diagram showing the configuration of a general disk format. One sector information includes a header section (ID) 11 that contains address information, and a CRC for checking errors in this header section 11.
12. Data section (Data) 1 containing data
3. It is basically configured with a CRC 14 for checking the data section 13 for errors.

Generally, when reading data from a magnetic disk, first, the header section 11 of sector information written on the disk is read, and whether or not an error has occurred in the address information of this header section 11 is checked. Check with CRC12. This CRC
12, if no error is detected, the data section 13 is subsequently read and it is determined whether or not an error has occurred in the data in this data section 13.
Check with CRC14. If no error is detected by this CRC14, the data section 13
The data stored in the computer is transferred to the main unit (for example, the host computer) as normal data. on the other hand,
If an error in the data section 13 is detected by the CRC 14, the main body is notified of this and the data in the data section 13 is prohibited from being transferred to the main body. As described above, it is a generally known method to perform an error check on both the header section and the data section of sector information when reading disk data.

Conventionally, when an error in the header section is detected, reading of data in the data section in the same sector information following the header section is stopped. For this reason, for example, even if a disk has a defect and it is known that the defect is only in the header section, the data in the data section cannot be read, and even if the data is normal, there is no way to save it. I couldn't.

[Problem to be solved by the invention]

As mentioned above, if there is a system that can absorb some data when a disk goes down for some reason, it is naturally easier to maintain than a system that cannot read any data (data in the data section). Sexuality also improves.

The present invention was developed in view of the above circumstances, and by recognizing a forced data reading command issued from the main body, it is possible to ignore the header part in the sector information and read the data in the data part in the same sector information. The purpose of the present invention is to provide a flexible disk data read control method.

[Means and actions to solve the problem]

The disk data read control method of the present invention is a method for reading sector information consisting of a header section and a data section, and includes: an error check means for checking errors in the header section; a read command output means for outputting a forced data read command; The apparatus further comprises a data part read control means for reading data in the data part by the forcible data reading command regardless of the error check result of the header part by the error checking means.

With this configuration, when a forced data read command is issued, even if there is an error in the header section, the error can be ignored and the data in the data section can be read, providing flexible disk data read control. becomes possible.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS A disk data read control system according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the circuit configuration. In FIG. 1, reference numeral 1 denotes a sector counter that counts sector pulses (SECTOR PULSE) arriving from a mechanical section (not shown). Reference numeral 2 denotes a sector register in which a sector value to be read is set by a command (SECTOR DATA) issued from the main body (for example, a host computer). Sector counter 1 and sector register 2 above
The value set to is output to the comparator 3. This comparator 3 is for detecting whether or not the magnetic head has reached the sector position set by the command. 4 is a control logic that controls the magnetic head when reading disk data and controls data transfer with the main body;
Reference numeral 5 denotes a CRC check circuit for checking the data in the header portion of the sector information read by the magnetic head.

Further, 6 is a flip-flop to which a forced data read command (SPECIAL READ) coming from the main body is set. 7 is the gate, CRC
The check result (ERROR) of the header section by the check circuit 5 is gated by the reset output of the flip-flop 6. This gate 7 is connected to the CRC check circuit 5 according to the contents of the flip-flop 6.
This control is provided to control whether or not to notify the control logic 4 and the main body of the result obtained (an error in the header section).

The operation of this embodiment will be described below with reference to the flowchart shown in FIG.

First, the operation when a forced data read command (SPECIAL READ) is not issued from the main body side will be explained. Note that the conditions for issuing this forced data reading command will be explained later.

When a forced data read command (SPECIAL READ) has not been issued (step S1),
Flip-flop 6 is in a reset state. First, the sector value set in sector register 2,
The sector values counted by sector counter 1 are compared by comparator 3. If a match is found here, the control logic 4 takes in the header data in the sector information from the disk and stores it.
Sends to CRC check circuit 5. In this case, the CRC check circuit 5 is a circuit that performs a CRC check on the header section of the header section and the data section that constitute the sector information. Data in the header section is generally read out before the data section. Therefore, the control logic 4 uses, for example, the data captured immediately after the sector pulse as the header data.
Sends to CRC check circuit 5.

The CRC check circuit 5 checks whether an error has occurred in the data in the header section.
The CRC (CRC12 shown in FIG. 3) is checked (step S2). Here, when the CRC check circuit 5 detects an error in the header section, it outputs a check result (ERROR) indicating the error to the gate 7. At this time, since the flip-flop 6 is not set, the gate 7 is in an open state.
Therefore, the check result (ERROR) of the CRC check circuit 5 is sent to the control logic 4 and the main body side (for example, the host computer) through this gate 7.
will be notified. As a result, in the control logic 4, for example, a built-in read gate (not shown)
function is killed, and the capture of the data part in the same sector information following the header part at this time is stopped. Further, on the main body side, as abnormal interrupt processing, for example, data reading operation is stopped (step S6).

On the other hand, if the CRC check circuit 5 does not detect any error in the header section, the control logic 4 reads the data in the data section in the same sector information following the header section (step S3).

Thereafter, the data in the data section taken into the control logic 4 is sent to, for example, a CRC check circuit (not shown) for checking the data section. this
The CRC check circuit checks the data section to see if an error has occurred in the data in the data section.
Check by CRC (CRC14 shown in FIG. 3) (step S4). If the result of this check is an error, that fact is notified to the main body side. As a result, the main body executes abnormal interrupt processing (step S6). On the other hand, if there is no error,
The data in the data section at that time is sent to the main unit as normal data. As a result, the main body side stores the data, for example, as normal interrupt processing (step S5).

Next, force data read command (SPECIAL
READ) is issued.

Now, for example, if a defect occurs in a certain sector and data cannot be read, and the user confirms that the cause is in the header, the user can force the data to be read from the main unit by operating the mode switch, etc. A read command (SPECIAL READ) shall be output. In other words, the conditions for issuing a forced data read command include, for example, when the data (data in the data section) cannot be read despite several data accesses and it is confirmed that the cause is in the header section. It is.

By outputting this forced data reading command (step S1), the flip-flop 6 is set. When flip-flop 6 is set, its output closes gate 7. When the gate 7 is closed, even if the CRC check circuit 5 detects an error in the header section, the check result (ERROR) is not notified to the control logic 4 and the main body side.

Therefore, when a forced data read command is output, the check result (ERROR) of the header section of the CRC check circuit 5 becomes invalid. In other words, the header section will be ignored. As a result, the control logic 4 takes in the data of the data section in the same sector information following this header section, regardless of the check result (ERROR) of the header section of the CRC check circuit 5 (step S3).

In this way, when the forced data read command is output, the data in the data section can be read regardless of the result of the error check of the header section by the CRC check circuit 5. Regarding the subsequent processing of the data section (steps S4, S5, S6)
(processing) is the same as the case where the above-mentioned forced data reading command is not issued.

〔Effect of the invention〕

As described above, according to the present invention, by issuing a forced data reading command from the main body side, it is possible to ignore the header part and read data in the data part within the same sector information. Therefore, if there is only an error in the header section, this error can be invalidated and the data in the data section within the same sector information can be retrieved.If an error occurs in the header section as in the past, the data section will be completely ignored. This greatly improves maintainability compared to a system in which it was not possible to collect data.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a circuit configuration according to an embodiment of the present invention, FIG. 2 is a flowchart for explaining the operation of the embodiment, and FIG. 3 is a diagram for explaining conventional data read control. FIG. 3 is a diagram showing the configuration of a disk format. 1...Sector counter, 2...Sector register, 3...Comparator, 4...Control logic,
5...CRC check circuit, 6...flip-flop, 7...gate.

Claims (1)

[Scope of Claims] 1. In a disk data read control method for reading sector information consisting of a header section and a data section from a disk through a magnetic head, an error check means for checking for errors in the header section read by the magnetic head; a read command output means for outputting a forced data read command for reading data in the data part in the sector information while ignoring the header part in the sector information; and the read command output means outputs the forced data read command. 1. A disk data read control system comprising: data section read control means for reading data in the data section regardless of the error check result of the header section of the error check section when the header section is checked.