JPS60138780A - Method for handling write inhibition - Google Patents

Abstract

PURPOSE:To attain much advantages on maintenance by inhibiting the write when write inhibition is indicated by a protection indication means and the address corresponds to a conventional storage area. CONSTITUTION:When an output of an inverting circuit 5 is logical ''1'', a write signal WR attains write through an AND gate 6. When the switch 1 is opened, an exclusive OR circuit 4 outputs respectively logical ''0'' and logical ''1'' depending on the logical ''1'' and logical ''0'' of the user storage area usage. The logical value is inverted by the inverting circuit 5 and logical values ''1'' and ''0'' are inputted to the AND gate 6. As a result, when the switch 1 is opened, the user's area is possible for write and the maintenance storage area is inhibited for write. Thus, the write of the maintenance storage area due to mistake of the user is inhibited so as to prevent destruction.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a storage device used in an information processing system, particularly to a method for handling write protection in a maintenance storage area in a magnetic disk device.

(b) Prior Art and Problems Magnetic disk drives are widely used as means for storing information in information processing systems. This magnetic disk device is equipped with a means, such as a protect switch, for prohibiting writing to the storage area in order to protect the stored data from destruction. However, when this protect switch is operated, writing to the entire storage area of the device is prohibited, and when this switch is released, writing to the entire storage area becomes possible.

Therefore, if maintenance personnel write to the maintenance storage area for some reason, releasing the protect switch will clear the entire storage area and cause an error in the address specification of the maintenance storage area. The drawback was that data in the user storage area could be destroyed.

(C1 Beyond the purpose of the invention, in view of the conventional drawbacks, the present invention aims to provide a write protection handling method that can cancel the write protection only in a maintenance storage area used when performing maintenance. .

(di) Structure of the Invention Briefly stated, the present invention provides a magnetic storage device that has a general storage area and a maintenance storage area, and has a write-protection function for the storage area, in which an address to be stored is in the general storage area. means for determining whether the storage area is a storage area or a storage area for maintenance, and a protection instruction means for maintenance, and the address corresponds to a general storage area when write protection is instructed by the protection instruction means. , the writing thereof is prohibited.

(e) Examples of the invention Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram showing one embodiment of the write protection handling method of the present invention, and FIG. 2 is a circuit diagram showing another embodiment of the present invention.

The decoding circuit 2 outputs a logical value, for example, "0" when the magnetic disk device specifies the address of the maintenance storage area, and outputs a logical value when the user storage area is specified.

1" is output. Switch 1 is a conventionally used protection switch, and when switch 1 is turned off, writing to the storage area is prohibited.

Both the switch 1 and the decoding circuit 2 are connected to an exclusive OR circuit 4. +5v is connected to the exclusive OR circuit 4 together with the output terminal of the switch l via the resistor element 3. The output of the exclusive OR circuit 4 is connected to one input terminal of an AND gate circuit 6 via an invert circuit 5, and the write signal WR is input to the other input terminal. Therefore, when the output of the invert circuit 5 becomes the logical value +11, the write signal ridge passes through the AND gate circuit G to perform writing. When the switch 1 is in the "open" state, one input of the circuit 4 has a logic value "1", and the exclusive OR circuit 4 has a logic value "1" for user storage use and a logic value "1" for storage use.
The logical values '0' and '1' are output depending on Oo, respectively. The logic values are each inverted by the Inverney circuit 5, and the logic values "1" and "0" are respectively input to the AND gate circuit 5. As a result, when switch I is "open", the user storage area is writable and the maintenance storage area is write-protected. That is, writing to the maintenance storage area due to a user's mistake is prohibited to prevent destruction. Next, when the switch l is "closed" and the logic value becomes °O', the exclusive OR circuit 4 outputs a logic value depending on the logic value °1" for user storage use and the logic value "0" for maintenance storage use. Value “l゛
and "0", which is inverted by the invert circuit 5, and outputs the input of the AND gate circuit 5 as a logic value "0" when the user storage area is used and a logic value "1" when the maintenance storage area is used. That is, when the switch is set to the "closed" state, the maintenance storage area becomes writable, and only writing to the user storage area is prohibited. The states of the above logical values are shown in the table below.

Table ``-11-Bottom-----Bottom 1111Bottom 11--] 1 switch 1 usage state 1 exclusive theory 1 inver 11 state 1
Output of 1 sum 1 to output 1 to--10--10--
--10--11+1 open "l"l 'l'l 'O' l
'l' 1+----10-----10-----10----
−-+1 open'l°1 "0°I "1'1"0" 1F
＝−−−10−−−−10−−−−10−−−−11 closed
0'1 °1' l "1° 1'0" 1 toe-
10～−−−+−−−−+−−−−−11 closed “0゛1”
Other embodiments will be described below with reference to FIG. 2.

The same symbols are used for the same parts as in FIG. The difference from the embodiment is that a switch 11 for inhibiting writing of the maintenance storage area is provided. When the decoding circuit 2 detects the user storage area, that is, when the logical value is "1", it is inverted by the invert circuit 12 regardless of whether the switch 11 is open or closed, and the AND circuit 14 becomes disconnected. Accordingly, the output of the AND circuit 10 becomes the logical value "1°" and "Oo," and the OR circuit has the logical value "1°" only when the switch l is open.
Outputs ゛ and allows writing. That is, depending on whether the switch 1 is opened or closed, writing to the user storage area is permitted or prohibited. If the maintenance storage area is used, that is, when the decoding circuit 2 outputs the logical value '0', the AND circuit 10 becomes disconnected regardless of whether the switch 1 is opened or closed.

Further, the AND circuit 14 becomes conductive only when the switch 11 is closed, outputs a logical value 'l'', and permits writing via the OR circuit 14. That is, when the switch 2 is closed, the storage area for maintenance is opened. becomes writable.

(f) Achievements of the Invention As explained above in detail, the write-protection handling method of the present invention allows the write-protection to be canceled only in the maintenance storage area used when performing maintenance. It has many advantages.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the write protection handling method of the present invention, and FIG. 2 is a circuit diagram showing another embodiment of the present invention. In the figure, ■ and 11 indicate switches, and 2 indicates a decoding circuit, respectively.

Claims (1)

[Claims] A means for determining whether an address to be stored is a general storage area or a maintenance storage area in a magnetic storage device that has a general storage area and a maintenance storage area and has a write-protection function for the storage area. and protection instruction means for maintenance, and when write prohibition is instructed by the protect instruction means, if the address corresponds to a general storage area, writing to the address is prohibited. Features: How to handle write protection.