Browse Prior Art Database

Radius Shell Tape Drive Positioning

IP.com Disclosure Number: IPCOM000051865D
Original Publication Date: 1981-Mar-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Roberts, SD: AUTHOR

Abstract

A high speed search for data may be accomplished on a reel-to-reel tape drive by employing radius shell information. This information is normally used to derive correct values for tension and acceleration currents for the motors at a given radius.

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Radius Shell Tape Drive Positioning

A high speed search for data may be accomplished on a reel-to-reel tape drive by employing radius shell information. This information is normally used to derive correct values for tension and acceleration currents for the motors at a given radius.

Each radius shell is logically derived by counting pulses from the tachometers mounted on the respective shafts of each motor. As Fig. 1 shows, each shell of tape corresponds to a particular length or zone of tape within the reel. The digital information describing each shell or zone is stored in the microprocessor of the drive logic whenever that particular shell occurs. Therefore, in order to perform a search at any speed of data through the length of a reel of tape, a digital compare may be made of the desired shell and the actual measured shell.

A high speed search by a tape drive may be implemented in this fashion ""disconnected'' from the control unit. The control unit issues a high speed search command to the drive to go to a certain tape zone (radius shell) along the tape; the drive then moves tape at a higher than recording speed to the desired zone, while the control unit becomes ""disconnected'' to do other work.

The length of the tape zones may be varied by adjusting the size (in bits) of the logic counters which count the tachometer pulses. A shell may vary from a single wrap of tape to as many wraps as is desired. Correspondingly, the tape zones could vary from a few inches to many feet.

With reference to Fig. 2 the length of tape between any two radii, r(1) and r(0), is given by:...