JPH0124799Y2 - - Google Patents

Description

[Detailed description of the invention] "Industrial application field" This invention is a magnetic bubble memory that automatically destroys the memory of the magnetic bubble memory attached to the device when it is attempted to be removed illegally. This paper relates to a memory destruction circuit for bubble memory.

"Prior Art" In various information processing devices, programs and various data are stored on magnetic disks or magnetic tapes, and the storage is read out and used as needed. Some of these programs and data are highly confidential. Keywords (passwords) are used for magnetic disks and magnetic tapes that store such information.If the password does not match, these magnetic disks will not be able to access the magnetic tape from outside. has been done.

However, magnetic bubble memory is used in the form of a cassette, for example, and can be accessed directly; keywords cannot be used, and anyone who can obtain magnetic bubble memory can read its memory contents. I can do it. From this point of view, there has been a need for measures to maintain the confidentiality of the contents stored in magnetic bubble memories.

The purpose of this invention is to provide a memory destruction circuit for a magnetic bubble memory, which automatically erases the memory contents when the magnetic bubble memory is illegally removed from the device.

``Means for solving the problem'' According to this invention, a destructive coil that can apply a magnetic field to erase the memory contents of the magnetic bubble memory is provided, and the magnetic bubble memory is prevented from being illegally removed from the device. Then, the destructive operation start switch is operated, and the operation of the switch automatically causes a destructive current to flow through the destructive coil from the destructive power source connected to the power supply terminal. This destructive current destroys the memory of the magnetic bubble memory, but a limiting means is provided to prevent the magnetic bubble memory from being physically destroyed.

"Embodiment" The figure shows an embodiment of a memory destruction circuit for a magnetic bubble memory according to this invention. A breaking coil 11 is provided as shown on the right side of the figure. This destruction coil 11
For example, an erasing coil built into a magnetic bubble memory cassette can be used, and by applying a memory destruction magnetic field to the magnetic bubble memory by passing a destruction current through the destruction coil 11, the polarity of all the bubbles is set in the same direction. It can be magnetized, meaning its stored contents can be erased.

Further, a plurality of destructive operation activation switches 12 are provided as necessary, which operate when the magnetic bubble memory is illegally removed from the device. For example, a destructive operation activation switch 12 is provided in association with the movable part of the door so that it will automatically operate if an attempt is made to open the door of a storage chamber in which a cassette of a magnetic bubble memory is housed. Also, if you try to remove the magnetic bubble memory cassette even slightly, the switch that operates immediately will activate the destructive operation activation switch 12.
It is established as From the viewpoint of increasing safety, it is preferable to provide a plurality of switches 12 so as to correspond to the various connections required to remove the magnetic bubble memory. Although not particularly shown in the figure, authorized operators can, for example, use keywords to
Alternatively, a key or a hidden release switch prevents the destructive operation from occurring even if the destructive operation activation switch 12 is activated.

A destruction power source is connected to power supply terminals 13 and 14 of this memory destruction circuit. In this example, power terminal 1
3 and 14 are connected to a power supply circuit 16 that converts the output of the commercial power supply 15 into direct current. Alternatively, the battery 17 is connected. In this example, the battery 17 is a secondary battery, the positive side of the battery 17 is connected to the terminal 13 , and the positive side of the power supply circuit 16 is connected to the power supply terminal 13 through a diode 18 . The negative side of the battery 17 is connected to the power supply terminal 14 through a power supply switching circuit 19 and further through a main switch 21 . The power supply terminal 14 is connected to the negative side of the power supply circuit 16 through the charging circuit 23 and further through the power supply switching circuit 19. Power switching circuit 1
9, as shown by the dotted line, the battery 17 and the main switch 21 are normally connected by the contact 24, and the negative side of the power supply circuit 16 is connected to the power terminal 14 by the switching contact 25.
and the other end of the charging circuit 23.

When the start switch 12 operates, the power terminal 13,
A breakdown current is applied to the breakdown coil 11 from a breakdown power supply connected to the breakdown coil 14 . In this example, when the start switch 12 operates, the relay is activated, and the breakdown current is caused to flow through the relay. This destructive current is also limited so that it does not physically destroy the magnetic bubble memory. For example, the start switch 12 is connected to the power terminal 13.
One end of the breaking coil 11 is connected, and the other end of the breaking coil 11 is connected to the power supply terminal 14 through a current limiting resistor 26, a relay contact 27a, and a switch 28.

Furthermore, in this example, when a destructive current is passed through the destructive coil 11 for a certain period of time, this current is automatically stopped, thereby preventing physical destruction of the magnetic bubble memory. That is, the start switch 12 is connected to the breakdown time limit circuit 29, and when the start switch 12 is turned on, a current flows through the relay coil 27c in the breakdown time limit circuit 29 for a certain period of time.

The switches 21 and 28 are interlocked and are turned on when the memory destruction circuit is put into operation. In this state, the transistor 3 connected in series with the relay coil 27c
1 base is given a high level. When the destructive operation start switch 12 operates (turns on) when the magnetic bubble memory is about to be removed, the voltage of the power supply terminals 13 and 14 is applied between the collector and emitter of the transistor 31 through the start switch 12, and the transistor 31 immediately becomes conductive. , a current flows through the relay coil 27c, and the contact 27 of the relay
a is turned on, a destructive current flows through the destructive coil 11, and the stored contents of the magnetic bubble memory are instantly destroyed.

At this time, even if an excessive current that physically destroys the magnetic bubble memory attempts to flow through the destruction coil 11, the current limiting resistor 26 limits the destruction current, and there is no risk of physically destroying the magnetic bubble memory. . Further, in the breakdown time limiting circuit 29, the capacitor 33 is charged through the resistor 32, and after a certain period of time, the Schmitt trigger circuit 34 is triggered and its output makes the transistor 31 non-conductive, and therefore the relay contact 27a is turned off. In this way, the magnetic bubble memory is prevented from being physically destroyed due to a destruction current flowing through the destruction coil 11 for a certain period of time or longer.

In this embodiment, both ends of the current limiting resistor 26 are connected to a breakdown current detection circuit 35, and when a breakdown current flows through the current limiting resistor 26 and the voltage across it exceeds a predetermined value, the breakdown current detection circuit 3
5, the detection output drives a breakdown confirmation circuit 36 made of, for example, a flip-flop, and the fact that a breakdown current has flowed is memorized, and this is displayed on, for example, a display element 37. Therefore, when memory destruction is performed on the magnetic bubble memory, this fact is stored in the destruction confirmation circuit 36. Therefore, even if the magnetic bubble memory is taken away, the destruction confirmation circuit 36 can confirm that its memory contents have been destroyed, meaning that there is no risk that the contents stored in the magnetic bubble memory will be stolen. This confirms that

Note that the battery 17 is constantly charged through the charging circuit 23 by the output of the power supply circuit 16.
Even in a state where no output is obtained from the power supply circuit 16 due to a power outage or the like, the memory destruction circuit operates as expected by the battery 17. When the battery 17 is not used, the contact 24 in the destructive power supply switching circuit 19 may be turned off, and the contact 25 may be switched to the power supply terminal 14 side. It is also clear that it can be operated using only the battery 17.

A voltage detection circuit 38 is connected to the power terminals 13 and 14 as necessary, so that the voltage between the power terminals 13 and 14 decreases and the memory of the magnetic bubble memory cannot be erased even if current is passed through the destruction coil 11. When the state is reached, the voltage detection circuit 38 detects this,
A sound message is emitted by displaying it on the display element 39 or the like. One of the switches 21 and 28 may be omitted.

``Effect of the invention'' As described above, according to the memory destruction circuit of this invention, when the magnetic bubble memory is about to be removed, the destruction operation start switch operates and the destruction current immediately flows through the destruction coil, causing the magnetic bubble Memory storage is destroyed. Therefore, even if the magnetic bubble memory is taken away, there is no risk that the previously stored contents will be stolen. Since the magnetic bubble memory is prevented from being physically destroyed even if the destruction operation activation switch is operated by mistake, the magnetic bubble memory can be used as a memory many times.

[Brief explanation of drawings]

The figure shows an embodiment of a memory destruction circuit for a magnetic bubble memory according to this invention. 11: Destruction coil, 12: Destruction operation start switch, 13, 14: Power supply terminal, 19: Destruction power supply switching circuit, 26: Current limiting resistor, 29: Destruction time limiting circuit.

Claims (1)

[Claims for Utility Model Registration] A destructive coil capable of generating a magnetic field that erases the memory contents of a magnetic bubble memory, a power supply terminal to which a power source for destruction is to be connected, and a device in which the magnetic bubble memory is illegally used. a destructive operation activation switch that operates when the magnetic bubble memory is about to be removed from the circuit and supplies a destructive current to the destructive coil through the power supply terminal; A memory destruction circuit for a magnetic bubble memory, comprising a limiting means for preventing.