JPH01143081A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To prevent secret data from being read by reading a pass-word signal to be written to one track with dividing a frequency band and next, reading a data signal. CONSTITUTION:An LPF 1 causes the pass-word signal, whose frequency is low, to be a pulse out of a load signal (a) and a low frequency read signal (b) is outputted. Then, an HPF 2 causes the data signal, whose frequency is high, to be the pulse out of the signal (a) and a high frequency read signal (c) is outputted. A shift register 3 converts the signal (b) to a bit parallel and the signal (b) is obtained as a read pass-word signal (e). Then, a comparator 4 compares the signal (e) and a pass-word signal D from a host device and when the signals are coincident, a readable signal (h) is sent to the host device. In the host device, when the signal (h) shows a true value, the output of a signal (d) is sent and the comparator 4 obtains a gate control signal (f) as the true value. Then, the signal (c) is outputted as an output read signal (g).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic disk device, and particularly to a magnetic disk device that uses a magnetic disk in which data and a password for accessing the data are written on the same track. The present invention relates to a magnetic disk device having a read circuit.

(Prior Art) Conventionally, in general, in a magnetic disk drive, only data is recorded on one track on the disk board, and when a read command is sent from the upper circuit, the data is immediately read and sent to the upper circuit. sending that data.

(Problems to be Solved by the Invention) In the above-mentioned conventional magnetic disk drive, if there is a continuous read instruction from the upper circuit, the read operation is performed only in accordance with that instruction. The disadvantage is that confidential data can be read out even if it is operated.

The purpose of the present invention is to eliminate such drawbacks and provide a confidential data protection function that records data and a password on one track and allows the data to be read only if the password is correct. An object of the present invention is to provide a magnetic disk device having the following features.

Note that even in the past, as a special example, something other than data is recorded on one track, but this is used for synchronization and has no relation to the protection of confidential data.

(Means for Solving the Problems) In order to achieve the above object, the magnetic disk device of the present invention uses two types of data signals having different frequency bands written on the same track on a magnetic disk plate. A magnetic disk drive includes a low-pass filter circuit 1 for extracting a data signal in a low frequency band from a data signal a written on the track and outputting it as a shaped pulse signal; A high-pass filter circuit M2 extracts a data signal in a high frequency band from the data signal a and outputs it as a shaped pulse signal α, and a shift register circuit converts the serial signal S output from the low-pass filter circuit 1 into a parallel signal e. 3, a comparator circuit 4 that compares the output signal e of the shift register circuit 3 and the password signal d sent from the upper circuit and outputs the comparison result f, and the output signal f of the comparator circuit 4. It has a gate circuit S that controls passage of the output signal C of the high-pass filter circuit 2.

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

FIG. 1 is a block diagram showing one embodiment of the present invention.

In FIG. 1, a low-pass filter circuit 1 is illustrated by a signal a (hereinafter referred to as a low read signal) that is not synchronized with a clock output from a circuit that handles analog signals of a magnetic disk drive (hereinafter referred to as a lower circuit). connected to lower-level circuits that do not.

The high-pass filter circuit 2 is also connected to various lower circuits as shown in the figure using the low read signal a. The shift register circuit 3 is connected to the low-pass filter circuit 1 for the low frequency read signal. The comparator circuit 4 is connected to the shift register circuit 3 with a read password signal e, and is connected to another data signal (hereinafter referred to as a password signal) d recorded on the same track at a frequency sufficiently lower than the frequency of the data signal and a read enable signal. It is connected to a circuit (hereinafter referred to as a lower circuit) of a magnetic disk loading and unloading device (not shown) located at a higher level. The gate circuit S is connected to a comparator circuit 4 using a gate control signal f, connected to a high-pass filter circuit 2 using a high frequency read signal C, and read directly to an upper circuit (not shown) using an output read signal g.

Next, the operation will be explained.

In one track of the magnetic disk of this embodiment, a data signal is written at a high frequency, and a password signal is written at a frequency sufficiently lower than the frequency of this data signal.

Therefore, when a read command is issued from the upper circuit to this magnetic disk device through a route not shown, the low read signal a includes a data signal and a password signal and is sent.

Among them, the low-pass filter circuit 1 performs waveform shaping on the low-frequency password signal of the low read signal a, converts it into a pulse, and outputs the low-frequency read signal S.

Mata, high pass filter circuit H-! , performs waveform shaping on the high frequency data signal of the low read signal a, pulses it, and outputs the high frequency read signal C.

Next, the shift register circuit 3 converts the low frequency read signal S into a bit paranol signal and generates a read password signal e.
Output as .

Next, the comparator circuit 4 receives the read password signal e.
and the password signal d sent from the upper circuit (not shown), and if they match, the read-enable signal is set, and the logic lf that previously corresponded to false logic corresponds to true.
It is sent as i to a higher-level circuit (not shown).

When the readable signal becomes a value indicating the truth of 1, the upper circuit (not shown) outputs the password signal d and issues a read command again.

When the password signal d is output, the comparator circuit 4 makes the gate control signal f correspond to logical truth.

When the gate control signal f corresponds to logical truth, the gate circuit 5 outputs a high frequency read signal C (a signal to be output as data) as an output read signal g.

As described above, in this embodiment, the password signal, which is the low frequency component of the low read signal a, is first read out and checked, and the data signal is read out only when the password signal is valid.

Therefore, even if you can operate the upper magnetic disk device control unit, if you do not know the password, the data signal will be lost. It cannot be read.

(Effects of the Invention) As explained above, the present invention writes data and passwords in one track in different frequency bands, and when reading data, first reads the password signal, and only when it is determined that the password is valid. Reading the data signal has the effect of preventing confidential data from being read by an operator who does not know the password.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. 1...Low pass filter circuit 2. High-pass filter circuit 3...Shift register circuit 401. comparator circuit 5...Gate circuit a...Low read signal b...Low frequency read signal C...High frequency lead signal d・0. password signal e・,・Read password signal f...-gate control signal g...Output read signal h...readable signal

Claims (1)

[Claims] In a magnetic disk device that writes two types of data signals with different frequency bands on the same track on a magnetic disk plate, a data signal in a lower frequency band is extracted from among the data signals written on the track. a low-pass filter circuit that outputs a shaped pulse signal; a high-pass filter circuit that extracts a high frequency band data signal from among the data signals written in the track and outputs it as a shaped pulse signal; and the low-pass filter. a shift register circuit that converts a serial signal output from the circuit into a parallel signal; a comparator circuit that compares the output signal of the shift register circuit with a password signal sent from the upper circuit; and outputs the comparison result; and the comparator circuit. A magnetic disk drive characterized by comprising a gate circuit that controls passage of an output signal of the high-pass filter circuit based on an output signal of the circuit.