Head selection technique

• US 4,270,154 A
• Filed: 05/24/1979
• Issued: 05/26/1981
• Est. Priority Date: 03/01/1978
• Status: Expired due to Term

• Current Assignee: John E. Crawford
• Original Assignee: John E. Crawford
• Inventors: Crawford, John E.
• Primary Examiner(s): Wolff, John H.
• Application Number:
  US06/042,201
• Time in Patent Office: 733 Days
• Field of Search: 360/97-99, 360/78, 360/72, 360/55, 360/63, 360/35, 360/137
• US Class Current: 360/78.04
• CPC Class Codes: G11B 15/12 Masking of heads; circuits for Selecting or switching of heads between operative and inoperative functions or between different operative functions or for selection between operative heads; Masking of beams, e.g. of light beams track selection by moving the magnetic head G11B5/54
• CPC Class Codes: G11B 27/105 of operating discs
• CPC Class Codes: G11B 5/012 Recording on, or reproducing or erasing from, magnetic disks G11B17/00, G11B19/00 take precedence
• CPC Class Codes: G11B 5/5556 with track following after a "seek"

Abstract

Method for recording and reading data in a disc storage unit is disclosed. The method includes providing a plurality of stacks of read/write heads mounted about the periphery of the disc pack. An additional feature includes the capability for prepositioning at least one of the stacks while another stack is performing a read or write operation. Also provided is means for simultaneously performing a separate read or write operation with each of at least two of the stacks. By the present invention, disc access time is minimized through a time based selection of an optimally located head.

Claims

1. In a magnetic disc imformation storage system in which a plurality of concentric information tracks on a rotating magnetic disc storage unit are each accessible by at least two radially movable magnetic read/write heads circumferentially spaced from one another, a method for selecting one of said at least two magnetic heads to perform a read or write operation on a predetermined sector of a predetermined information track in response to a command signal, comprising the steps of:

(a) determining a candidate magnetic head in response to the instantaneous position of the predetermined sector relative to the magnetic heads;

(b) calculating the time it will take the candidate head to traverse from its instantaneous radial position to the radial position of the predetermined information track;

(c) selecting the candidate head as the magnetic head to perform the read or write operation if the candidate head is capable of reaching the radial position of the predetermined information track prior to the time the predetermined sector passes the candidate head on the first revolution of the storage disc after receipt of the command signal;

(d) selecting another magnetic head as the head to perform the read or write operation if said other head is capable of reaching the radial position of the predetermined information track prior to the time said predetermined sector passes the other head on the first revolution of the storage disc and if the candidate head cannot reach the predetermined information track prior to the time the predetermined sector passes the candidate head on the first revolution of the storage disc; and

(e) selecting the magnetic head which is first able to reach the radial position of the predetermined information track prior to the time the predetermined sector passes it on a subsequent rotation of the storage disc as the head to perform the read or write operation if neither magnetic head is capable of reaching the radial position of the predetermined information track on the first revolution of the storage disc.

2. The method of claim 1 wherein said step of determining the candidate magnetic head includes the steps of:

establishing an assignment chart indicating the magnetic head each sector will first pass after each increment of rotation of a magnetic storage disc;

detecting when the magnetic storage disc is at a reference position during the rotation thereof;

measuring the elapsed time since the storage disc was last at the reference position when a command signal is generated;

determining the next magnetic head which a predetermined sector will pass by reference to the assignment chart and the elapsed time; and

selecting the determined magnetic head as the candidate magnetic head.

3. The method of claim 1 further including the steps of:

generating a second command signal while a previous read/write operation is being performed to indicate a subsequent read/write operation to be performed;

carrying out steps (a)-(e) to select the proper magnetic head for the subsequent operation; and

5. The method of claim 3 further including the step of initiating the subsequent read/write operation as soon as the selected magnetic head is operatively positioned with respect to the sector of the information track to be utilized in the subsequent operation, regardless of whether the previous operation is completed.

7. The method of claim 5 further including the step of carrying out the second read/write operation as soon as the second selected magnetic head reaches an operative position with respect to the information track sector on which the second operation is to be performed and prior to the time the first operation is completed, to thereby perform two read/write operations simultaneously.

4. positioning the magnetic head selected for the subsequent operation at the radial position of the information track to be utilized during the subsequent operation prior to the time the previous operation is completed if the selected magnetic head is other than the magnetic head utilized in the previous operation.

6. In a magnetic disc information storage system in which a plurality of concentric information tracks on a rotating magnetic disc storage unit are each accessible by at least two radially movable magnetic read/write heads circumferentially spaced from one another, a method for reducing disc access time, comprising the steps of:

generating a first command signal indicating a first read/write operation to be performed on a sector of an information track on a disc storage unit;

selecting one of the magnetic heads to perform the read/write operation in dependence upon the time it takes each of said magnetic heads to reach an operative position with respect to the indicated sector;

carrying out the first read/write operation with the selected magnetic head;

generating a second command signal, prior to the completion of the first read/write operation, indicating a second read/write operation to be performed;

selecting a magnetic head other than the magnetic head selected for the first operation to perform the second read/write operation; and

initiating the positioning of the magnetic head selected for the second read/write operation towards the radial location of the information track to be used in the second operation prior to the time the first read/write operation is completed.