JPS6192477A - Medium defect detecting system - Google Patents

Abstract

PURPOSE:To prevent an error at data reading by measuring it at a count means when a pulse shaper smoothes a prescribed value continuously and outputting a medium defect detecting signal detecting a defect existing in a medium based on the measurement. CONSTITUTION:If a defect exists on a magnetic disc, an output of a head H is very small and the pulse shaper 3 outputs continuously an H level signal. Thus, a timer 6 is not reset but counts a clock outputted from a variable frequency oscillator 4. When no data is inputted for a specified time or over and the H level signal is consecutive, since the time 6 counts clocks by a prescribed number, '1' is outputted. A flip-flop 7 outputs '1', outputs an error signal representing detection of defect to display detection of defect, and the result is fed to a demodulation circuit 5, from which a clamp signal outputting '1' consecutively is generated. Thus, malfunction due to change into a random data is prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a medium defect method for detecting a defect in a medium, and particularly to a method for accurately detecting a medium defect in a magnetic disk. This is what I did.

(Prior Art) As shown in FIG. 3(a), addresses and recording data are written on a magnetic disk in a conventional magnetic disk device, so that recording data can be written at a predetermined address. A synchronization byte SYo for indicating the read position of the address is written before the address, and a synchronization byte SY for indicating the read position of the recorded data is written before the recorded data. Then check code C such as ECC or CRC
o is written, and a similar check code C1 is written next to the recorded data to check whether or not the address or recorded data has been correctly read.

[Problem that the invention seeks to solve]

In such conventional magnetic disk devices, as mentioned above,
The read addresses, recorded data, etc. were only checked to see if they were accurate using a check code. Therefore, as shown in FIG. 3(b), when a medium error E exists immediately before the synchronization high l-5Yo,
Output from the demodulation circuit occurs as if data similar to the synchronization byte existed in this part, and even if addresses or recorded data are read incorrectly, these addresses or recorded data will be reproduced as if they were read normally. There was a drawback that it could be stored away.

In other words, in the conventional technology, since the recording density of the medium was low and the data modulation/demodulation method was relatively simple, the occurrence of the above-mentioned defects was rare, and this type of error did not pose much of a problem.

However, as the recording density of media has increased in recent years, the occurrence of media defects such as those described above has been increasing.
Due to the complexity of the demodulation method, after the data in the media defect area is demodulated, it becomes a bang similar to a synchronous byte, making it impossible to determine the error and detecting the defect too late. It became necessary to detect media errors.

C. Means for Solving Problems] Therefore, to solve the problems as described above, when reading data with a magnetic disk device, the demodulator determines whether or not there is a defect in the medium, and when reading data caused by a defect in the medium. This is to minimize errors and to quickly detect the content of the error.For this purpose, the medium defect detection method of the present invention uses an amplification unit that reads data recorded on the medium and amplifies the signal. , a pulse shaper that differentiates the output signal from this amplification section, and a timer means R[
The present invention is characterized in that when the pulse shaper continues to maintain a constant value, the timer measures this and outputs a medium defect detection signal for detecting a defect existing in the medium based on this.゛[Operation] This makes it possible to detect defects in the medium, thereby minimizing errors during data reading due to defects in the medium, as well as quickly identifying the nature of the error. can be done.

〔Example〕

An embodiment of the present invention will be described based on FIGS. 1 and 2. FIG.

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG. 2 is an explanatory diagram of its operation.

In the figure, 1 is an amplifier that amplifies the output signal generated from the rad H for reading the magnetic disk, and 2 is an automatic gain control circuit that keeps the output signal of the amplifier 1 constant. Item 3 is a pulse shaper that differentiates the read signal and converts the analog signal into a digital signal.After detecting the peak of the analog signal,
It outputs a digital signal as shown in FIG. 2(A). 4 is a variable frequency oscillator that generates a clock according to the speed of the motor, 5 is a demodulation circuit, 6 is a timer that counts the clock output from the variable frequency oscillator 4, and 7 is a flip-flop that generates a clamp signal. The output, IO, is a demodulator.

The demodulator 10 converts the signal read from the magnetic disk into "1".
, "0" signal, and includes a variable frequency oscillator 4, a demodulation circuit 5, a timer 6, a flip-flop, and the like. And (summer circuit 5 is flip-flop 7
As will be described later, when an error signal indicating detection of a medium defect is output, this error signal is input as a clamp signal and the output data is clamped to, for example, all "0".

Next, the present invention will be explained in detail.

If there is no defect in the magnetic disk, the signal read from the head H, passed through the amplifier 1 and the automatic gain control circuit 2, and output from the pulse shaper 3 is as shown in FIG. 2(A).
This is a signal in which H level and L level are mixed for a short period of time. As a result, the variable frequency oscillator 4 outputs a clock according to the rotational speed of the magnetic disk to the timer 6, and the timer 6 counts this clock. However, this timer 6 is reset by the application of the L level signal from the pulse shaper 3 before it has counted the clock output from the variable frequency oscillator 4 by a predetermined number of times.
If there is no defect in the magnetic disk, this timer 6 is “0”.
", and the flip-flop 7 does not output an error signal. The demodulation circuit 5 then discriminates the signal output from the pulse shaper 3 using the clock output from the variable frequency oscillator 4 and outputs "1" and "Oj."In this way, the demodulation circuit 5 outputs "1". , “
A signal of "0" is outputted using the NRZ method, for example, and sent to the host device.

However, if there is a defect in the magnetic disk, the output of the head H becomes extremely small as shown in FIG. 4, and as a result, the output of the pulse shaper 3 becomes The H level signal will be output continuously. Therefore, the timer 6 counts the clock output from the variable frequency oscillator 4 without being reset. Then, when no data is input for a specified time T or more and the H level signal continues, time t
1, the timer 6 counts the specified number of clocks and outputs "1" as shown in FIG. is output to indicate that a defect has been detected, and at the same time, this "1" is applied to the demodulation circuit 5.As a result, the demodulation circuit 5 becomes a clamp that continuously outputs "1" as shown in FIG. 2(C). It will generate a signal.

As a result, conventionally, the defect signal shown in FIG.
However, according to the present invention, when abnormal data is detected, it is possible to clamp it. Therefore, based on this change to random data (no malfunction will occur), this clamp signal can be sent to the host device as error status information on the device side.

This enables early detection of error contents, improves the reliability of data transfer, and can also be applied to data protection.

Moreover, as shown in Figure 4, if there is a long defect, in the case of a circuit configuration in which data demodulation is performed using a variable frequency oscillator, data will not be input to the variable frequency oscillator for a long time, resulting in a loss of synchronization and an abnormal lock (Loclc). ), the demodulation cannot be performed with only the re-read command, and therefore it is necessary to re-synchronize, resulting in time loss and the like, and further reducing the reliability of data transfer. In the present invention, in order to prevent the occurrence of such abnormal locks,
Alternatively, in order to quickly detect a defect as described above, when such a defect exists, it can be detected and an error signal can be generated, so that it can be applied as a countermeasure against abnormal locking of this variable frequency oscillator.

In the above description, the timer 6 is of a counter type, but of course the timer 6 is not limited to this type, and other types may be used.

〔Effect of the invention〕

According to the present invention, when there is a medium defect, it is detected, an error signal is output, and the output of the demodulation circuit is clamped, so that it is possible to improve the conventional drawback that random data is output due to a medium defect and malfunction occurs. Moreover, errors during data reading caused by medium defects can be minimized.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of its operation, FIG. 3 is an explanatory diagram of magnetic disk recording data, and FIG. 4 is an explanatory diagram of medium defects. In the figure, 1 is an amplifier, 2 is an automatic gain control circuit, 3 is a pulse shaper, 4 is a variable frequency sporadically-converter, 5 is a demodulation circuit, and 6
is a timer, 7 is a flip-flop, and 10 is a demodulator.

Claims (1)

[Claims] It is equipped with an amplifying section that reads data recorded on a medium and amplifies the signal, a pulse shaper that differentiates the output signal from the amplifying section, and a timer, and when the pulse shaper continues to maintain a constant value. The medium defect detection method is characterized in that a medium defect detection signal for detecting a defect existing in the medium is output based on the measurement by the time measuring means.