Tape positioning using reverse boundary capture: tape drive system and method
AssigneeHewlett-Packard Company
InventorBradfred W. Culp
Life of this patent
Estimating the term…
Abstract
A tape driven system includes means for capturing data block boundaries while moving in reverse, as well as in the forward direction. Thus, block boundaries can be captured following each reversal of tape direction to cancel prior errors induced during tape reversals provided these errors are within tolerance. In a hitch operation, the rear boundary of a data block is recaptured as a reference position for the next forward operation. In a backspace operation, the front boundary of a data block is captured while the tape is moving in the reverse direction to provide a reference point for the next operation.
Claims19
A method of positioning a tape relative to a transducer head, said method comprising the steps of:
- moving said tape by said head in a forward direction a first time;
- capturing a tape position indicator value of a block-to-gap boundary;
- inhibiting boundary capturing while ramping down to stop;
- ramping the tape up to speed in the reverse direction;
- activating boundary capturing when said tape is within a predetermined value of said captured tape position indicator value of said block-to-gap boundary;
- capturing a position indicator value of a next-detected gap-to-block boundary whereby said position indicator value of said next-detected gap-to-block boundary substantially reflects only the error due to a single tape direction reversal;
- inhibiting capturing while ramping down to stop;
- and
- moving the tape in the forward direction a second time, activating boundary capturing when said tape is within a predetermined value of said captured tape position indicator value of said next-detected gap-to-block boundary, and positioning said next-detected gap-to-block boundary of said tape relative to said transducer head sufficient to essentially restrict position error to a differential stretch over the ramp up distance and a single tape reversal.
A method of providing reference positions for more precise positioning of blocks of data stored on a tape relative to a read head of a tape drive system, said tape drive system being capable of transferring said tape in a forward direction so that said tape can be read, said tape drive system being capable of transferring said tape in a reverse direction so that said tape can be repositioned, said blocks of data being arranged serially along said tape, adjacent blocks being spaced by interblock gaps, said interblock gaps having a predetermined nominal minimum length, each block having an associated front boundary and an associated rear boundary said tape drive system having a position indicator for indicating position values relative to a physical position along the length of a tape, said position indicator being subject to errors induced in part during accelerations and decelerations of said tape during starts, stops and reversals of tape motion, said method comprising the steps of:
- inhibiting boundary capture;
- moving said tape in the reverse direction;
- activating boundary capture when said position value of said position indicator is within a predetermined value of a captured position value and;
- capturing at least one of said front and rear boundaries of a block for providing a reference position for more precise positioning of blocks of data stored on said tape relative to said read head of said tape drive system.
A tape drive system for reading information from a tape medium, said information being stored in a series of data blocks separated by interblock gaps, each block having an associated rear boundary, said interblock gaps having a predetermined nominal minimum length, said tape drive system comprising:
- a read head;
- drive means for transferring a tape across said read head, including means for transferring said tape in a forward direction and in a rearward direction, means for starting and stopping said tape, and means for increasing and decreasing the speed of said tape;
- position indicator means for assigning position values reflecting changes in tape position relative to said head;
- boundary capture means for capturing a boundary between a block and a gap, including means for capturing a boundary between a block and a gap while a tape is moving in a reverse direction;
- controller means for controlling said drive means, said drive controller means being in communication with said position indicator and said boundary capture means so as to have access to current and stored position values;
- capture inhibit means for being responsive to said drive controller means so that data blocks other than one being positioned around can be ignored while said tape is moving and not operable within a predetermined value of said captured boundary to prevent improper boundary capture during repositioning said tape relative to said rear head.
Dependencies are inferred from the claim text.