JPS6141961A - Crush detecting system - Google Patents

Abstract

PURPOSE:To enable crush detection by storing AGC voltage in each cylinder at the time of mounting or changing a disk medium and comparing with AGC voltage in the state of use at present. CONSTITUTION:AGC voltage is written on a memory 13 in order of cylinders through an A/D convertor 12 at the time of mounting or changing a disk medium. As AGC voltage fluctuates during seeking in ordinary state of using, normal AGC voltage of each cylinder stored in the memory 13 is read out after on- track, and inputted to a terminal of a comparator 16 through a D/A convertor 15 as a reference signal, and AGC voltage in the state of present use is inputted to another terminal of the comparator 16. Normal AGC voltage of each cylinder is compared with present AGC voltage, and if there is abnormality, an alarm is given and its crush is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a crash detection method, and more particularly to a method for detecting the occurrence of a crash (medium abnormality) during use of a magnetic disk medium.

Generally, when a magnetic disk is in use, an AGC control circuit as shown in FIG. 3 is used to control the read voltage between the magnetic disk medium 1 and the head 2 as shown in FIG. This is because even in magnetic disks, the head output voltage differs between the center and the periphery due to the difference in media speed, that is, the output voltage differs depending on the cylinder, so this is controlled to maintain a constant output voltage. .

As shown in FIG. 3, the output of the magnetic head 2 is amplified by a preamplifier 3 and then input to an AGC amplifier 4.
The output is input to the peak holding circuit 5, and the peak value for each gate is held. The peak values for each gate are added by the amplifier 6 and fed back to the AGC amplifier 4 as an AGC control voltage, thereby generating a constant voltage regardless of the outer or inner circumference of the disk.

In the magnetic disk reproduction and demodulation circuit as described above, when the head 2 comes into contact with the magnetic disk medium, the magnetic film formed on the aluminum plate is often scratched or peeled off, damaging the magnetic disk medium.

The present invention relates to early detection of such damage.

[Conventional technology]

The conventional method used to detect such an abnormality is to compare the AGC control voltage with a DC reference voltage, as shown in Figure 4, and to generate an alarm if an abnormal voltage occurs due to a crash. It's a method.

[Problem that the invention seeks to solve]

Even in normal conditions, the AGC control voltage has different values depending on the radius of the cylinder, and in the conventional method described above, since a constant DC voltage is used as the reference voltage, Differences in crash detection levels due to differences in output at the outer periphery, etc., cannot be resolved, and this is inconvenient for perfect crash detection.

[Means and effects for solving the problems] The present invention provides a crash detection method that solves the above problems. The output is applied to a peak hold circuit to hold the peak value, generate a control voltage based on the peak value, feed back to the amplifier, compare the control voltage with a reference voltage, and prevent the head of the magnetic disk from crashing. In this method, when replacing the medium of the magnetic disk, an unwritten read-only memory (ROM) is prepared together with the medium, and a value obtained by analog/digital conversion of the control voltage for each magnetic disk is stored in the read-only memory. and compares the control voltage for each disk written in the read-only memory when the head is in actual use with the control voltage in the use state, and generates an alarm if there is an abnormality in the use state. It is done by method.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which 11
is a low-pass filter, 12 is an A/D converter, 13 is a memory, 1
4 is a control circuit, 15 is a D/A converter, and 16 is a comparator.

In the present invention, when a disk is exchanged, an unwritten read-only memory 13 is prepared together with the medium, and A/D converted AGC control voltages for each cylinder are written therein. In the usage state, the normal AGCIJ? of each cylinder written in the memory 13 during on-track except during seek is correct. II voltage and current AG
C*J# voltage is compared, and if it is abnormal, an alarm is reported, and as information to minimize data destruction, measures such as transferring the data to another disk medium or magnetic tape are taken.

In addition, at the input of the control circuit 14 in FIG.
B is an input terminal for a signal for distinguishing between seek and on-trunk operations, and C is an input terminal for a signal indicating the number of cylinders.

Next, the present invention will be explained in detail.

(b) After turning on the power when installing or replacing a disk medium,
Seek-on-track each cylinder in order (sequence seek), and write the AGC voltage of each cylinder to the memory (ROM) after A/D exchange.

(b) During normal use, the AGC control voltage fluctuates during seek, so when the seek is completed and on-trunk, that is, when read/write is possible, the memory corresponding to the number of cylinders of the track (
AGC on ROM)! LJ? 11 Read voltage, D/A
After conversion, it is compared with the current AGC*I'a voltage, and if it is in the direction of greatly increasing the gain, an abnormality (crash) is detected.

(Effects of the Invention) As described in detail above, according to the present invention, the AGC system
The a voltage (during on-trunk) is memorized for each cylinder when the medium is loaded or replaced, and compared during actual use to detect abnormalities in the AGC control voltage, i.e., servo disk, head,
This method detects abnormalities in head amplifiers, cables, etc., and is convenient because crash detection can be performed taking into account differences in crash detection levels due to differences in AGC control voltage due to differences in cylinders.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the crash detection method according to the present invention, FIG. 2 is a diagram showing the mutual relationship between the magnetic head and the magnetic disk medium, and FIG. 3 is a diagram showing the magnetic head output control circuit. Block Diagram Showing One Example FIG. 4 is a block diagram showing one example of a conventional crash detection method. In the figure, 11 is a low-pass filter, 12 is an A/D converter, 13 is a memory, 14 is a control circuit, 15 is a D/A converter, and 16 is a comparator.

Claims (1)

[Claims] The output of the head of the magnetic disk is amplified by an amplifier, the output of the amplifier is applied to a peak hold circuit to hold the peak value, and the peak value generates a control voltage, which is fed back to the amplifier to control the control voltage. In the method of detecting a crash of the head of the magnetic disk by comparing the voltage with a reference voltage, when replacing the medium of the magnetic disk, an unwritten read-only memory (ROM) is prepared together with the medium, and the read-only memory (ROM) is A value obtained by analog/digital conversion of the control voltage for each of the magnetic disks is written in, and the control voltage for each disk written in the read-only memory when the head is in an actual use state is compared with the control voltage in the use state. The flash detection method is characterized in that an alarm is generated if there is any abnormality in the usage condition.