JPH04274004A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To provide a magnetic disk device capable of reducing the read error due to shoulder noise and the read error due to the reduction of amplitude and capable of increasing a read margin. CONSTITUTION:This device is provided with a power source fluctuation detection circuit 3 preliminarily recording the level switching information 106 to control the threshold voltage of the threshold on the surface of magnetic disk medium, detecting the power source fluctuation and outputting a power source fluctuation information 7, RAM 2 outputting the control signal to control the threshold voltage (k) by level switching information 106 and the power source fluctuation information 7 to signal lines 104, 105, and switches 7, 8 switching the threshold (k) by the control signal from the RAM 2. The threshold k1, k2 switched by the switches 7, 8 are inputted in a level detection circuit 1 reading the data on the surface of the magnetic disk medium. When power source fluctuation occurs, the threshold voltage in the level detection circuit 1 is set to the optimum value corresponding to the fluctuation and the data on the surface of the magnetic disk medium is read.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive, and more particularly to a level detection circuit for signal detection during power fluctuations.

0002

[Prior Art] Conventionally, in this type of magnetic disk device,
The threshold voltage in the level detection circuit is set to a constant value and cannot be changed.

0003

[Problems to be Solved by the Invention] As mentioned above, in conventional magnetic disk drives, the threshold value in the level detection circuit fluctuates when power supply fluctuations occur, resulting in shoulder noise due to crosstalk noise from adjacent cylinders. This method has the disadvantage that it is easy to cause errors in detecting signals or errors in not detecting signals due to a decrease in the amplitude of the waveform.

An object of the present invention is to solve the above-mentioned drawbacks by setting the threshold voltage of the level detection circuit to an optimal value in response to power fluctuations, and to prevent read errors caused by shoulder noise. It is an object of the present invention to provide a magnetic disk device that can reduce read errors caused by vibration and amplitude reduction and can increase read margin.

[0005]

[Means for Solving the Problems] A magnetic disk device of the present invention includes a level detection circuit that takes in data on the surface of a magnetic disk medium, performs level detection by comparing it with a threshold value for detecting a read signal, and reads out the data. In the magnetic disk device, control information for controlling the threshold voltage of the threshold is recorded in advance on the magnetic disk medium surface,
a power supply fluctuation detection circuit that detects power supply fluctuations and outputs power supply fluctuation information; a random access memory (hereinafter abbreviated as RAM) that outputs a control signal that controls a threshold voltage based on control information and power supply fluctuation information; The threshold value from the switching circuit is input to the level detection circuit to read data on the surface of the magnetic disk medium.

[0006]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a read circuit of a magnetic disk device according to an embodiment of the present invention.

In FIG. 1, the readout circuit of this embodiment is as follows:
Level detection circuit 1, RAM 2, and power fluctuation detection circuit 3
, resistors 4, 5, and 6, and switches 7 and 8.

The level detection circuit 1 receives signals on a signal line 101 and a signal line 103 and outputs a read signal on a signal line 102. The RAM 2 loads threshold voltage level switching information 106 in response to power supply fluctuations, which has been recorded in advance on the magnetic disk medium surface of the magnetic disk device. The power supply fluctuation detection circuit 3 transmits power supply fluctuation information 107 to the RAM 2 when the power supply voltage V2 fluctuates. As a result, the RAM 2 outputs a control signal for switching the switches 7 and 8 based on the level switching information 106 and power supply fluctuation information 107 that have been read in previously, and switches the switches 7 and 8 via the signal line 104 and the signal line 105. ON/
Turn off. The resistors 4 to 6 are connected in series, with a voltage V1 applied to one terminal and the other terminal grounded. A switch 7 is connected to the connection point between the resistors 4 and 5, and a switch 8 is connected to the connection point between the resistors 5 and 6.

Next, the specific operation will be explained below.

FIG. 2 is a waveform diagram showing signal waveforms at various parts in FIG.

In FIGS. 1 and 2, the magnetic disk device records level switching information 106 for switching the detection level in the level detection circuit 1 on a magnetic disk medium, reads it at the time of starting up the device, and stores the level switching information 106. Store it in RAM2.

When the power supply voltage V2 increases and the threshold voltage of the level detection circuit 1 decreases, the power supply fluctuation detection circuit 3 monitors the power supply voltage V2 and transmits power fluctuation information 107 of the power supply fluctuation to the RAM 2. . The RAM 2 outputs a control signal for switching the switches 7 and 8 based on the stored level switching information 106 and power fluctuation information 107, and turns on the switch 7 via the signal line 104.
Then, the switch 8 is turned off via the signal line 105. By turning on the switch 7, the threshold voltage k of the level detection circuit 1 becomes k=k2 via the signal line 103. Shoulder noise a generated due to the influence of crosstalk noise from adjacent tracks is detected when the threshold voltage is k=k1 due to power supply fluctuations and appears as a pulse a0 on the signal line 102, but changes to k=k2. As a result, the pulse a0 is no longer generated and no read error occurs.

Further, when the power supply voltage V2 decreases and the threshold of the level detection circuit 1 increases, the power supply fluctuation detection circuit 3 monitors the power supply voltage V2 and stores power fluctuation information 107 of the power supply fluctuation in the RAM 2. tell. The RAM 2 turns on the switch 8 via the signal line 105 and turns off the switch 7 via the signal line 104 in response to the power supply fluctuation information 107.
F. By turning on the switch 8, the signal line 10
3, the threshold voltage of the level detection circuit 1 is k=k1
becomes. Waveform b on the signal line 101, whose amplitude has decreased due to pattern effects, media defects, etc., is not detected when the threshold voltage is k=k2 due to power fluctuations, and no pulses are generated on the signal line 102. , causing a read error. By switching the threshold voltage to k=k1, the waveform b whose amplitude has decreased is also detected, and a pulse b0 is generated on the signal line 102, thereby preventing read errors from occurring.

As described above, even if the threshold voltage of the level detection circuit 1 fluctuates due to fluctuations in the power supply voltage V2, the lead margin can be improved by always setting the threshold voltage to an optimal value in response to the fluctuation. Make it bigger.

In this embodiment, the threshold voltage is switched in two stages, but the switching stages are not limited to this, and it is also possible to switch in many stages.

[0017]

As explained above, the magnetic disk drive of the present invention eliminates shoulder noise by setting the threshold voltage of the level detection circuit to an optimal value in response to power fluctuations. This has the effect of reducing read errors caused by this method and read errors caused by amplitude reduction, and increasing the read margin.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a read circuit of a magnetic disk device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing signal waveforms at various parts in FIG. 1;

[Explanation of symbols]

1 Level detection circuit 2 RAM 3 Power supply fluctuation detection circuit 4, 5, 6 Resistors 7, 8 Switches 101, 102, 103, 104, 105 Signal line 106 Level switching information 107 Power supply fluctuation information a Shoulder noise b Waveform a0, b0 Pulse k , k1 , k2 threshold V1 , V2 power supply voltage

Claims (1)

[Claims] 1. A magnetic disk device comprising a level detection circuit that takes in data on a magnetic disk medium surface, performs level detection by comparing it with a threshold value for detecting a read signal, and reads out the data. a power fluctuation detection circuit that records control information for controlling the threshold voltage of the threshold on a medium surface, detects power fluctuation and outputs power fluctuation information; and the control information and the power fluctuation information. a random access memory that outputs a control signal for controlling the threshold voltage, and a switching circuit that switches the threshold voltage according to the control signal from the random access memory; A magnetic disk device characterized in that input is input to the level detection circuit and data on the surface of the magnetic disk medium is read.