Dynamic magnetic information storage or retrieval – Head – Core
Patent
1994-06-29
1997-04-29
Donaghue, Larry D.
Dynamic magnetic information storage or retrieval
Head
Core
395894, 360 69, G06F 1312, G06F 9445, G11B 1910
Patent
active
056257996
ABSTRACT:
A method and apparatus for determining the logic and functionality of a disk changeline. By attempting to reset the changeline and monitoring the changeline for a change in state, the present invention determines whether a changeline is functional. When the present invention does not immediately observe a change in state, the present invention accesses the disk drive to determine whether a disk is present in the drive. When a disk is present in the drive, the present invention reads the changeline and stores the read value as a disk present value. When the present invention has previously determined that the changeline is functional, the present invention inverts the disk present value to create a disk not present value. When a disk is not present in the disk drive, the present invention stores the read value of the changeline as the disk not present value. Having obtained a disk not present value, the present invention compares the obtained value with a known active changeline state of a machine using an inverted logic. When the disk not present value is not equivalent to the active changeline value of the inverted logic machine, the present invention determines that the changeline employs normal logic and is functional. On the other hand, when the disk not present value is equivalent to the active value of the inverted logic machine, the present invention compares the floppy disk not present value with the floppy disk present value. When the floppy disk not present value is equivalent to the floppy disk present value, the present invention determines that the changeline is not functional. Conversely, when the floppy disk not present value is not equivalent to the floppy disk present value, the present invention determines that the changeline employs inverted logic and is functional.
REFERENCES:
patent: 5173816 (1992-12-01), Ogihara
patent: 5293625 (1994-03-01), Miura et al.
patent: 5301293 (1994-04-01), Kano
IBM Technical Reference, Pesonal Computer AT Systems BIOS 5, ROM BIOS Code Listing for Floppy Controller, IBM, 1985, pp. 97-115.
Donaghue Larry D.
Microsoft Corporation
Rinehart Mark H.
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