JPS63249975A - Magnetic disk controller - Google Patents

Abstract

PURPOSE:To prevent data from being destroyed with write to a program area or the like due to a software bug by providing a write inhibit track setting circuit, a write track designating circuit, and a comparator circuit. CONSTITUTION:First, a write inhibit track is set to a write inhibit track setting circuit 201 and write inhibition is indicated. In the case of write access to a magnetic disk device 101 by higher software from a higher controller 102, the track is outputted to a write track designating circuit 202. If the output result coincides with the inhibit track set to the write inhibit track setting circuit 201, the output indicating this coincidence is outputted from a comparator circuit 203 and an inhibit indication, namely, write inhibit flag is set to a write inhibit flag circuit. Thus, destruction of data important with respect to hardware is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk control device, and particularly to a magnetic disk control device that allows new data to be superimposed on any designated track (or sector) on which data has already been written. This relates to a magnetic disk control device that can be prohibited.

[Prior Art] Conventionally, this type of magnetic disk control device has permitted writing by issuing a write permission command using software. Therefore, if you try to write new data to the same specified track where data or programs have already been written, if a write permission command has been issued on the software, the new data will be written to the old specified track. Data and programs are erased and saved within the specified track.

[Problems to be solved] As mentioned above, with conventional magnetic disk control devices, it is possible to write to any designated track if write permission is granted by software, so a software bug can cause valuable data to be destroyed. The disadvantage was that it could be damaged.

[Means for Solving Problems] A magnetic disk control device of the present invention that solves the problems of the prior art described above includes a write-inhibited track setting circuit for any designated track, and a write track designation circuit that operates based on instructions from software. and a comparison circuit that compares the specified track specified by the write-inhibited track setting circuit with the write track specified by the write-track designation circuit, and a prohibition flag when both tracks are the same in the comparison circuit. and a write-inhibit flag circuit for setting the write-inhibited track, thereby preventing writing to the write-inhibited track.

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

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

In the drawing, 100 is a magnetic disk control device, and 200 is a magnetic disk control device.
201 is a control circuit, 201 is a write-inhibited track setting circuit for any designated track, 202 is a write-track designation circuit that operates based on instructions from software, and 203 is a designated track designated by the write-inhibited track setting circuit 201 and write-track designation. A comparison circuit 204 compares whether or not the write track specified by the circuit 202 is the same, and a write prohibition flag circuit 204 sets a prohibition flag when the two tracks are the same in the comparison circuit 203.

Next, the operation of the magnetic disk control device of the present invention will be explained. First, a write-inhibited track is set in the write-inhibited track setting circuit 201, and a write-inhibited instruction is issued. When there is a write access to the magnetic disk device 101 by higher-level software from the higher-level control device 102, that track is output to the write track designation circuit 202. When the output result matches the prohibited track of the write prohibited track setting circuit 201, the comparison circuit 203 outputs an output to that effect, and a write prohibited flag is displayed in the write prohibited flag circuit, that is, a write prohibited flag is set. Upon detection of this write-inhibited flag, the magnetic disk control device 100 notifies the higher-level control device 102 that "an access was made to a write-inhibited area" and stops writing to the magnetic disk device 101. In this manner, the magnetic disk control device of the present invention prevents valuable hardware data from being destroyed.

Note that it is also possible to share the write-inhibited track setting circuit 201, the write track designation circuit 202, and the comparison circuit 203 using a ROM or the like.

[Effects of the Invention] As explained above, the magnetic disk control device of the present invention has the following effects:
A write-protected track setting circuit for any specified track, a write-track designation circuit that operates based on instructions from software, a specified track specified by the write-protected track setting circuit, and a write track specified by the write-track designation circuit. By having a comparison circuit that compares the two tracks, and a write prohibition flag circuit that sets a prohibition flag when both tracks are the same in the comparison circuit, it is possible to prevent writing to the prohibited track in terms of hardware, and therefore prevent software bad data. This has the effect of preventing data destruction due to writing to the program area, etc.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of a magnetic disk control device of the present invention. 100: Magnetic disk control device 101: Magnetic disk device 102: Upper control device 200: Control circuit 201: Write-inhibited track setting circuit 202: Write-in track designation circuit 203: Comparison circuit 204: Write-inhibited flag circuit

Claims (1)

[Claims] A write-protected track setting circuit for any specified track, a write-track designation circuit that operates based on instructions from software, a specified track specified by the write-protected track setting circuit, and a write track specified by the write-track designation circuit. and a write prohibition flag circuit that sets a prohibition flag when both tracks are the same in the comparison circuit, thereby preventing writing to the write prohibited track. A magnetic disk control device characterized by: