JPH04153902A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To reduce a read error due to shoulder noise and the read error due to an amplitude drop by changing over the threshold voltage of a level detection circuit. CONSTITUTION:A level detection circuit 1 inputs a signal on a signal line 101 and a signal line 103 and outputs the signal on a signal line 102. A RAM 2 reads in the information of a head address and a cylinder address preliminarily recorded on the medium surface of a magnetic disk device. It turns ON/OFF switches 6 and 7 via a signal line 104 and a signal line 105 corresponding to the information of a head address signal 106 and a cylinder address signal 107. Accordingly, the threshold voltage of the level detection circuit 1 can be changed over corresponding to the head address and cylinder address. Thus, the read error due to shoulder noise and the read error due to amplitude drop are reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk drive, and more particularly to a magnetic disk drive equipped with a level detection circuit for signal detection.

[Conventional technology]

Conventionally, in this type of magnetic disk drive, the threshold voltage in the level detection circuit has been set to a constant value and has not been changed.

[Problem to be solved by the invention]

In the conventional magnetic disk drive described above, the threshold voltage in the level detection circuit is constant regardless of the position where the data to be read is written. This method has the disadvantage that errors in detecting noise and errors in not detecting signals due to a decrease in the amplitude of the waveform in the inner circumferential cylinder are likely to occur.

[Means to solve the problem]

In the magnetic disk drive of the present invention, in the level detection circuit in the reading means of the magnetic disk drive, the information for controlling the threshold voltage for detecting the read signal is taken in from the medium surface on which the information is recorded, and the information is taken in as a head address signal. A RAM that outputs a signal that controls a threshold voltage for detecting a read signal in response to a cylinder address signal.
and a switching circuit that switches the threshold voltage using a signal that controls the threshold voltage.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

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

Referring to FIG. 1, this embodiment has a level detection circuit 1 and an RA
It is composed of M2, resistors 3-5, and switches 6-7. The level detection circuit 1 has a signal line 101 and a signal line 10.
3 is input, and the signal is output onto the signal line 102. The RAM 2 reads head address and cylinder address information previously recorded on the medium surface of the magnetic disk device. Then, the head address signal 10
6 and cylinder address signal 107,
Switches 6 to 7 are connected via signal line 104 and signal line 105.
Turn on/off. The resistors 3 to 5 are connected in series, and a voltage (1) is applied to one terminal, and the other terminal is grounded. A switch 6 is connected to the connection point between the resistors 3 and 4, and a switch 7 is connected to the connection point between the resistors 4 and 5.

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

The magnetic disk device records detection level switching information in the level detection circuit 1 on a medium, reads it out when the device is started up, and stores the level switching information 108 in the RAM 2. When the head address signal 106 and the cylinder address signal 107 are input to the RAM 2, the head address information for the outer cylinder or the head address that is largely affected by crosstalk noise is inputted, the RAM 2 turns on the switch 6 via the signal line 104, and outputs the information via the signal line 105. Turn off switch 7. By turning on the switch 6, the signal line 10
3, the threshold voltage K of the level detection circuit l becomes K''
It becomes K2. Shoulder noise a generated due to the influence of crosstalk noise from adjacent tracks is detected when the threshold voltage K = 1 and the signal! ! However, by changing K= to 2, the pulse a(,) no longer occurs, and read errors no longer occur.

Furthermore, when information about the inner circumferential cylinder or the head address where the amplitude tends to decrease is input using the head address signal 106 and the cylinder address signal 107, the RAM 2
turns on the switch 7 via the signal line 105, and the signal line 1
Switch 6 is turned off via 04. By turning on the switch 7, the threshold voltage of the level detection circuit 1 becomes ≦ through the signal line 103. In a cylinder head where the output voltage is small and is prone to amplitude reduction due to media defects, if the threshold voltage is 2, the signal line 1
The waveform whose amplitude has decreased on 01 is not detected and the signal line 102
The upper pulse no longer occurs, causing a read error.

By switching the threshold voltage to 1, the waveform causing the amplitude drop is also detected and a pulse B is generated on the signal line 102. occurs, and the read error will no longer occur.

As described above, by switching the threshold voltage of the level detection circuit 1 in accordance with the head address and cylinder address, the read margin can be increased.

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

〔Effect of the invention〕

As explained above, the present invention has the excellent effect of reducing read errors due to shoulder noise and read errors due to amplitude reduction by switching the threshold voltage of the level detection circuit, and increasing the read margin. . In addition, information on the head address and cylinder address for switching the signal detection level is recorded on the medium of the magnetic disk device, and is read out and stored in the RAM when the device is started up. Another effect is that it is possible to set a level switching address.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a magnetic disk device according to the present invention, and FIGS. 2(a) and 2(b) are waveform diagrams showing waveforms at various parts of FIG. 1, respectively. 1...Level detection circuit, 2...RAM, 3-ra...
・Resistance, 6-7...Switch.

Claims (1)

[Claims] In the level detection circuit in the reading means of the magnetic disk device, the information for controlling the threshold voltage for detecting the read signal is taken in from the surface of the medium on which the information is recorded, and the information is read in from the surface of the medium in which the information is recorded, A magnetic disk device comprising: a RAM that outputs a signal that controls a threshold voltage for detecting a read signal; and a switching circuit that switches the threshold according to the signal that controls the threshold voltage. .