JPH05101552A - Magnetic disk device - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to detect an abnormality in the read clock in a magnetic disk device and report an error that can be retried in case of a data read abnormality due to a head position shift. To do. [Structure] Data read by the head 1 is demodulated and pulsed, a read clock synchronized with the pulsed data is created, and the data is decoded using the clock,
In the magnetic disk device that converts the read data into the read data and sends the read data to the host device 13, a detecting means 11 is provided for monitoring the pulse cycle of the pulsed data and detecting an abnormality in the pulse cycle. The result is sent to the host device 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device, and more particularly, to a magnetic disk device which detects an abnormality in a read clock and reports a data read abnormality due to a positional shift of a head so that a retry is possible. Disc device

In recent years, a magnetic disk device is required to have a large capacity, a high function and a small size, and in order to achieve a large capacity and a small size, a data writing density on a disk medium has been increased. There is.

By increasing the density, the distance between the data tracks becomes narrower, and even if the amount of displacement of the head with respect to the data track is the same as in the conventional case, the data read operation cannot be performed. ing.

However, the positional displacement of the head may be temporary due to residual vibration immediately after the positioning operation, and the positional displacement of the head may be suppressed in some cases. By the way, when a part of read data cannot be demodulated, the magnetic disk control device retries the same portion on the disk medium and sends the normally read data, which is not a big problem for the computer system. However, when the data read operation itself cannot be executed due to the displacement of the head, the magnetic disk device reports an error as an error with the highest priority.

When this abnormality report is made several times,
This magnetic disk device is determined to be a defective device. However, if it is determined that the device is defective, the computer system has a serious problem that the data stored in the magnetic disk device cannot be used. Even if possible, it is desirable to have retryable error reports with low priority.

[0006]

2. Description of the Related Art FIG. 3 is a block diagram for explaining an example of a conventional technique, and FIG. 4 is a detailed block diagram of a clock generation circuit.

The data read by the head 1 is the well-known RLL.
(Run Length Limited) 1-7 or 2-7 code based on code logic, which is demodulated by the data demodulation circuit 2,
It is pulsed and sent to the clock generation circuit 3 and the decoding circuit 4.

On the other hand, the read command sent from the host device is input to the read / write command decoder 7 via the interface circuit 5, and the read command is decoded, and the clock control circuit 6 and the decode circuit 4 receive the read command. Sent out.

Since the clock control circuit 6 has been notified that the command is a read command, it controls the clock generation circuit 3 so that the data demodulation circuit 2 sends a pulsed signal 1-7.
Alternatively, the read clock is generated in synchronization with the 2-7 code.

Therefore, the clock creating circuit 3 creates a clock for data reading by the pulsed 1-7 or 2-7 code and sends it to the decoding circuit 4. Since the decoding circuit 4 is a read command, the decoding circuit 4 decodes the pulsed 1-7 or 2-7 code transmitted by the data demodulation circuit 2 using the read clock transmitted by the clock generation circuit 3 and outputs it in bit units. Is sent to the interface circuit 5 as read data.

The clock generation circuit 3 has a structure as shown in FIG. 4, and the phase difference detection circuit 8 has a phase difference between the pulsed data sent by the data demodulation circuit 2 and the clock sent by the voltage controlled oscillation circuit 10. Is detected and a control signal is sent to the voltage controlled oscillator circuit 10 through the filter 9 so that this phase difference disappears.

Therefore, the voltage controlled oscillator circuit 10 oscillates at a frequency synchronized with the pulsed data sent by the data demodulation circuit 2 and sends a data read clock. FIG. 5 is a diagram for explaining the normal operation of FIG. 4, and FIG. 6 is a diagram for explaining the abnormal operation of FIG.

The phase difference detection circuit 8 includes a data demodulation circuit 2
From this, pulsed data as shown by RAWDT in FIG. 5 is inputted, and a clock pulse as shown by CLK is inputted from the voltage controlled oscillation circuit 10.

Then, the phase difference between RAWDT and CLK is detected, and the filter 9 causes the voltage controlled oscillation circuit 10 to INC.
And a control signal as indicated by DEC is transmitted. And
When the RAWDT pulse is delayed from the clock CLK as shown in FIG. 7, the DEC pulse width becomes wider as shown in, and the signal becomes a signal that delays the phase of the oscillation frequency of the voltage controlled oscillator circuit 10. As shown in, the RAWDT pulse becomes When it advances from CLK, the pulse width of INC widens as shown by, and it becomes a signal that advances the phase of the oscillation frequency of the voltage controlled oscillation circuit 10.

When the data cannot be read due to the displacement of the head 1, the pulse waveform cannot enter the phase difference detection circuit 8 as shown in RAWDT of FIG. In the case of the 1-7 or 2-7 code, the number of consecutive logic "0" s is up to 7, and if the logic "0" continues beyond this, the operation of the phase difference detection circuit 8 becomes abnormal, and FIG. The INC pulse is no longer transmitted as indicated by the INC in FIG.
As shown in, the pulse width of DEC becomes wider.

The frequency of the clock generated by the voltage controlled oscillator circuit 10 gradually decreases and the pulse width gradually increases, as indicated by CLK in FIG.

[0017]

As described above, when the data cannot be read due to the displacement of the head, the frequency of the clock is lowered, but the magnetic disk device controls the read operation in synchronization with the clock. Therefore, the read operation control becomes abnormal.

That is, although the range of each sector is set based on the clock for read control, the extended range of the clock causes the sector range to be erroneous, and the read operation is performed until the next sector.

Therefore, the sync byte indicating the beginning of the data of the next sector cannot be read, and an abnormality report of a sync byte miss with a high priority is issued. Since the conventional magnetic disk device does not detect the abnormality of the read clock,
When a sync byte miss is reported, the magnetic disk controller cannot judge that the read operation control is abnormal due to the head position shift, and it can judge that it is a defective device although the offset read operation enables recovery. However, as described above, when it is determined that the device is a defective device, the computer system cannot use the data of the magnetic disk device, resulting in a serious loss that leads to a system down.

In view of the above problems, the present invention detects a read clock error and allows a retry from the magnetic disk controller before the read operation control becomes abnormal. As a result, the purpose is to minimize the influence on the computer system by making the magnetic disk control device report and retry.

[0021]

FIG. 1 is a block diagram for explaining the principle of the present invention. In the magnetic disk device, the data demodulation circuit 2 demodulates the data read by the head 1 into a pulse, and the clock creation circuit 3 creates a read clock synchronized with the pulsed data, and the data is decoded by using this clock. 12 decodes it, converts it into read data, and sends it to the host device 13.

A detection means 11 for monitoring the pulse cycle of the pulsed data and detecting an abnormality in this pulse cycle is provided, and the detection result of this detection means 11 is passed through the decoding means 12 to the host device 13. To send to.

Further, in the magnetic disk device, the data read by the head 1 is demodulated by the data demodulation circuit 2 to be pulsed, the read clock synchronized with this pulsed data is generated by the clock generation circuit 3, and this clock is used. The data is decoded by the decoding means 12, converted into read data, and sent to the host device 13.

Then, the pulse cycle of the pulsed data is monitored to detect the abnormality in the pulse cycle, and the read data of the read data is sent to the host device 13 based on the detection result of the detecting means 11. Instead, it is provided with a decoding means 12 for sending data for notifying the occurrence of a retryable error, and when this detecting means 11 detects an abnormality, it reports a retryable error to the host device 13.

[0025]

With the above-described structure, the magnetic disk device immediately reports a retryable error to the host device 13 when the read clock becomes abnormal. I.e.,
Before reading up to the next sector, the magnetic disk device can be instructed to retry.

Therefore, since the magnetic disk device retries at the same location, the data can be read successfully when the positional displacement of the head 1 is suppressed. If the positional displacement of the head 1 continues, the offset read operation succeeds in reading the data.

Therefore, the magnetic disk device is not judged as a defective device, and the influence on the computer system can be minimized.

[0028]

1 is a block diagram of a circuit showing an embodiment of the present invention. The same reference numerals as those in FIG. 3 denote the same functions.
The anomaly detection circuit 14 monitors the period of the pulse that the data demodulation circuit 2 demodulates the 1-7 or 2-7 code,
When "0" continues for 8 or more or logic "1" continues for 3 or more, it is determined that the clock is abnormal and an abnormal signal is sent to the decoding circuit 15.

When the decoding circuit 15 receives this abnormal signal, it masks the data sent by the data demodulation circuit 2 and sends all "00" data to the interface circuit 5.

Through the interface circuit 5, all "0"
Receiving the data of 0 ″, the host device 13 recognizes that a read error has occurred, and causes the magnetic disk device to perform an operation of rereading the same portion on the magnetic disk medium again or a position of the head 1. Is offset slightly and an offset read instruction is issued to perform the operation of reading the same portion on the magnetic disk medium again.

[0031]

As described above, the present invention detects that the read clock is abnormal and reports it as a retryable error to the magnetic disk control device. It becomes possible to cause the magnetic disk device to retry before an abnormality occurs.

Therefore, even if the data cannot be read due to the displacement of the head, it is possible to prevent the magnetic disk device from becoming a defective device, and the influence on the computer system can be minimized. I can.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating the principle of the present invention.

FIG. 2 is a block diagram of a circuit showing an embodiment of the present invention.

FIG. 3 is a block diagram illustrating an example of a conventional technique.

FIG. 4 is a detailed block diagram of a clock generation circuit.

FIG. 5 is a diagram for explaining the normal operation of FIG.

FIG. 6 is a diagram for explaining an operation at the time of abnormality in FIG.

[Explanation of symbols]

 1 head 2 data demodulation circuit 3 clock generation circuit 4, 15 decoding circuit 5 interface circuit 6 clock control circuit 7 read / write command decoder 8 phase difference detection circuit 9 filter 10 voltage control oscillation circuit 11 abnormality detection means 12 decoding means 13 Host device 14 Abnormality detection circuit

Claims (2)

[Claims] 1. A data read by a head (1) is demodulated and pulsed, a read clock synchronized with the pulsed data is created, the data is decoded using the clock, and converted into read data. In the magnetic disk device for sending to the higher-level device (13), a detection means (11) for monitoring the pulse cycle of the pulsed data and detecting an abnormality in the pulse cycle is provided. A magnetic disk device, wherein the detection result is sent to the host device (13). 2. The data read by the head (1) is demodulated and pulsed, a read clock synchronized with the pulsed data is created, the data is decoded using the clock, and converted into read data. In the magnetic disk device for sending to the host device (13), the detection means (11) for monitoring the pulse cycle of the pulsed data and detecting an abnormality in the pulse cycle, and the detection means (11) Decoding means (12) for sending data notifying the occurrence of a retryable error to the host device (13) instead of the read data based on the result
And a magnetic disk device, wherein when the detection means (11) detects an abnormality, a retryable error report is sent to the host device (13).