JPS61228544A - Write protection system - Google Patents

Abstract

PURPOSE:To detect a write state to a test area and to protect completely the write state by adding a means to a magnetic disk device to inhibit the writing carried out from a host device as necessary. CONSTITUTION:Both upper and lower limit inhibiting areas are stored in the upper and lower limit address memory circuits 11 and 12 of a write protection system respectively. Then the read or write address designated by a host device is stored in a read/write address memory circuit 20. An upper limit comparator 31 compares the contents of both circuits 11 and 20 with each other, while a lower limit comparator 32 compares the contents of both circuits 12 and 20 with each other. An AND circuit 40 secures an AND between outputs of both comparators 31 and 32, and a read/write indicating circuit 50 indicates the distinction between the read and write states. An AND circuit 60 secures an AND between the outputs of both circuits 40 and 50, and a valid/invalid indicating circuit 70 indicates the valid or invalid of each action. Then an AND circuit 80 secures an AND between both circuits 50 and 60. The circuits 40, 60 and 80 detect the write state to a test area for complete protection of the write state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk device, and particularly to a write protection method thereof.

[Conventional technology]

Generally, when testing a magnetic disk device, the test often includes the recording medium as well. Therefore, there is a possibility that valuable data may be destroyed. Various measures have been taken to prevent such data destruction. As a conventional means for preventing data destruction of this type, a method is known in which a test area is reserved in advance and writing is performed only in this area. With this method, it is necessary to be aware of the location of the reserved area in the test program, and if a device with a different location of the test area is added, the test program must be modified accordingly.
There was a drawback that if this correction was made incorrectly, areas other than the test area would be destroyed.

[Problem that the invention seeks to solve]

An object of the present invention is to provide the magnetic disk device itself with a function of storing a test area and a function of detecting an attempt to write to an area other than the area and reporting without writing. To provide a write protection method for a magnetic disk device that is capable of more reliable write protection.
be.

[Failure to solve the problem]

According to the present invention, a write-protected area storage means for storing a write-protected area, a read/write address storage means for writing a read/write address, and a read/write instruction means for instructing a read/write distinction. , comparison means for comparing the contents of the write-protected area storage means and the contents of the read/write address storage means;
There is provided a write protection method capable of detecting unauthorized writing to a magnetic disk device, comprising an unauthorized writing detection means for detecting unauthorized writing from the output of the comparison means and the output of the read/write instruction means. can get.

〔Example〕

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

A write protection system according to an embodiment of the present invention includes an upper limit address storage circuit 11 that stores the upper limit of the write-protected area, a lower limit address storage circuit 12 that stores the lower limit of the write-protected area, and a write protection system that stores the upper limit of the write-protected area. a read/write address storage circuit 20 that stores the read or write address to be read, an upper limit comparison circuit 31 that compares the contents of the upper limit address storage circuit 11 and the contents of the read/write address storage circuit 20, and a lower limit address storage circuit 1.
2 and the content of the subsequent write address storage circuit 20, an AND circuit 40 that takes the logical product of the outputs of the upper limit comparison circuit 31 and the lower limit comparison circuit 32, and the read/write distinction. Instructing Sogome instructions one after another! r5
0, ANI) output of the circuit 40 and the read/write instruction circuit 50
an AND circuit 60 that performs logical product with the output of
and an AND circuit 80 which takes the logical product of the output of the AND circuit 60 and the output of the validity/invalidity indicating circuit 70.

The successive write instruction circuit 50 outputs "1" for writing and "0" for successive writing, and the validity/invalidity instruction circuit 70 outputs "1" for valid and "0" for invalid. shall be taken as a thing. Furthermore, the contents of the upper limit address storage circuit 11 and the lower limit address storage -wr12 are respectively fixed to predetermined values in this example, but the contents of the upper limit address storage circuit 11 and the contents of the lower limit address storage circuit 12 are It is also possible to give it from a higher-level device.

Next, the operation of the write protection system having such a configuration will be explained.

When it becomes necessary to write to a certain area (fixed area in this example) of the magnetic disk device, the output of the valid/invalid instruction circuit 70 is set to "1" in accordance with an instruction from the host device.

Under such circumstances, when there is a read or write request from the host device, the address on the disk device to be read or written is sent to the read 1 address storage circuit 20, and the distinction between read and write is indicated. The data to be read and written are respectively set in the read/write instruction circuit 50. Address data set in the read/write address storage circuit 20 is supplied to an upper limit comparison circuit 31 and a lower limit comparison circuit 32. Here, the upper limit comparison circuit 31 compares the supplied address data with the contents of the upper limit address storage circuit 11, and when the former is smaller than or equal to the latter, it becomes "1".
is output, and “0” is output otherwise. The lower limit comparison circuit 32 compares the supplied address data with the contents of the lower limit address storage circuit 12, and outputs "1" when the former is greater than or equal to the latter, and outputs "0" otherwise. .

Now, when the supplied address data is smaller than or equal to the contents of the upper limit address storage circuit 11 and larger than or equal to the contents of the lower limit address storage circuit 12, the outputs of the upper limit comparison circuit 31 and the lower limit comparison circuit 32 are both"
1", the output of the AND circuit 40 becomes "1"; otherwise, it becomes "O". Successive write instruction circuit 5
If the output of 0 is "1", that is, in the case of writing, and the output of the AND circuit 40 is "1", the output of the AND circuit 60 is "1"; otherwise, it is "0". ” becomes. AN
I) When the output of the circuit 60 is "1", that is, when the address data given from the host device is within the upper and lower limits of the write-protected area and the operation requested by the host device is writing. In this case, the output of the AND circuit 80 is “1”.
This output signal is useful for inhibiting writing and as an unauthorized writing report signal to the host device.

If it is not necessary to write to the magnetic disk device, the write enable/disable instruction circuit 7
Set the output of 0 to “O”. In this case, the AND circuit 60
The output of the AND circuit 80 is always 0 regardless of the output of
Therefore, writing is not inhibited and unauthorized writing is not reported to the higher-level device.

〔Effect of the invention〕

As explained above, the present invention provides a magnetic disk device with
By adding a means to prohibit writing from the host device as necessary, it is possible to prevent data corruption due to bugs or other causes in the magnetic disk drive test program executed on the host device. .

[Brief explanation of the drawing]

The drawing is a block diagram showing one embodiment of the present invention. 11... Upper limit address storage circuit, 12...
...Lower limit address storage circuit, 20...Read/write address storage circuit, 31...Upper limit comparison circuit, 3
2...lower limit comparison circuit, 40...AND
Circuit, 50... Read/write instruction circuit, 60...
. . . AND circuit, 70 . . . Validity/invalidity instruction circuit, 80 . . . AND circuit. Agent Patent Attorney Uchihara n Shiro

Claims (1)

[Claims] a write-protected area storage means for storing a write-protected area; a read/write address storage means for storing a read/write address;
read/write instruction means for instructing read/write distinction; comparison means for comparing the contents of the write-protected area storage means with the contents of the read/write address storage means; 1. A write protection system for a magnetic disk device, comprising unauthorized write detection means for detecting unauthorized writing from an output of a read/write instruction means.