Abstract: Disclosed is a magnetic disk apparatus comprising a memory storing data received from an external apparatus via an interface, a magnetic head for writing to the magnetic disk the data stored in the memory, a falling detection unit for detecting falling of the magnetic disk apparatus, an acceleration detection unit for detecting acceleration applied to the magnetic disk apparatus, a reception interruption unit for, when the falling detection unit detects the falling, interrupting the sending/receiving operation of the data and command at the interface, interrupting the writing operation of the magnetic head to the magnetic disk, and escape the magnetic head from the magnetic disk, and a reception restoring unit for, after the acceleration detected by the acceleration detection unit lowers under a predetermined value, overwriting to the magnetic disk the data stored in the memory using the magnetic head.

Abstract: An agravity sensor is a mechanical switch which is opened in an agravity state. A CPU determines based on the output from this agravity sensor if the self apparatus is falling. If it is determined that the self apparatus is falling, the CPU instructs an IDE interface controller to transmit an unload command for retracting a magnetic head to an HDD. At this time, the CPU uses, as the unload command, a reset signal independent from general commands such as a read signal, write signal, and the like, which are processed by the HDD in the order they are accepted.

Abstract: An apparatus, primarily for use in battery-powered floppy disk drives, for moving a magnetic head radially toward a reference track in accordance with a direction signal from a disk controller. The apparatus comprises a track position sensor for sensing the track position of the magnetic head. The track sensor outputs a signal indicating whether the magnetic head is positioned radially inward or outward of track positions within a predetermined vicinity of a magnetic disk reference track. The apparatus has a reset circuit for generating a set signal when a power is applied to the reset circuit, and a logic circuit responsive to the track sensor output and set signal for providing a first binary control signal for use in selecting the direction of movement of said magnetic head. A second logic circuit utilizes the first binary control signal and the direction signal from the disk controller to provide a second binary control signal operative to set the direction of movement of the magnetic head.

Abstract: In the head positioning control system in the magnetic disk device of the index servo system of the invention, a position signal representing the position of the head on the disk, generated by a position signal generator, is converted by an A/D converter into a digital signal. Based on the digital signal, a CPU determines positioning correction data. The CPU stores positioning correction data in a memory, converts it into an analog signal by a D/A converter, and drives a stepping motor through a distributor and a magnetizing circuit so as to correct the position of the magnetic head.

Abstract: A positioning apparatus for a magnetic disk drive apparatus including a biasing means for returning a carriage on which the magnetic head is mounted to a fixed position whenever a power source for the apparatus is cut off, and force compensation circuits operably connected to the carriage for supplying the carriage with an opposite force equivalent to the force of the biasing means as a function of the magnetic head position relative to the disk. The control force compensation circuits the speed of the carriage as it changes position from one track to another track and maintain the magnetic head in proper position over the selected track once it is reached.

Abstract: A servo track configuration has a plurality of magnetized unit regions provided on the servo sectors of a magnetic disk so that they may be sequentially disposed in four positions predetermined on the servo tracks at prescribed space intervals from each other, the magnetized unit regions at each position being spaced apart from each other at space intervals equal to two-track width and each having a length of two-track width. The disposition of said magnetized unit regions provided in said four positions is made such that when one magnetized unit region is taken as a reference, the remaining are disposed sequentially shifted by one-track width from said one magnetized unit region in one direction.

Abstract: A velocity control system for a magnetic disc apparatus has: a circuit for generating a two-phase position signal which is used to determine the position of the magnetic head; an A/D converter for converting the two-phase position signal to a digital signal; a microprocessor for computing a target velocity and a real velocity which correspond to a distance between the target track and the current position of the magnetic head in accordance with the digital signal, and for computing a velocity difference between the target velocity and the real velocity; a D/A converter for converting a signal corresponding to the velocity difference to an analog signal; and a linear motor for driving the magnetic head to control the seek velocity of the magnetic head, in accordance with the analog signal.

Abstract: A magnetic disk apparatus utilizing both fixed and removable disk mounted on a common spindle, wherein a first head-positioning device for supporting a first group of magnetic heads cooperating with fixed disk and a second head-positioning device for supporting a second group of magnetic heads cooperating with removable disk means are independently controlled in operation; a drive spindle, fixed disk, first group of magnetic heads and first head positioning device are received in an enclosure, which is removably mounted on a base casting and shot off from dust particles; the removable disk is exposed to the outside of the enclosure; and the second head-positioning device is securely mounted on the base casting.

Abstract: A servo track apparatus comprising at least one unit pattern area including 2n (n=2, 3, 4, . . . ) servo tracks T.sub.i (i=0, 1, . . . 2n-1) and 2n.sup.2 flux transitions R.sub.jk (j=0, 1, . . . 2n-1; k=0, 1, . . . n-1). The tracks and flux transitions satisfy a condition TT requiring that track T.sub.p be adjacent to track T.sub.p+1 ; a condition TR requiring that transition R.sub.pq occur on track T.sub.p+q (mod 2n); a condition RR requiring that transitions R.sub.pq and R.sub.pr (r.noteq.q) have the same polarity and occur at the same position; and a condition RR requiring that transitions R.sub.pr and R.sub.qr (q.noteq.p) occur at different positions.