Tape positioning using reverse boundary capture: tape drive system and method

Claim 3

The method of claim 1 further comprising the step of: after capturing the position of said gap-to-block boundary, and before ramping down to a stop in the reverse direction, capturing the next-detected block-to-gap boundary.

Claim 6

The method of claim 3 further characterized in that said at least one boundary is said front boundary.

Claim 7

The method of claim 3 further characterized in that said at least one boundary is said rear boundary.

Claim 8

The method of claim 5 further characterized in that said front boundary is also captured while the tape is moving in reverse.

Claim 9

The method of claim 5 further characterized in that said activating boundary capture is the step of enabling a gap-to-block boundary capture mode before capturing said rear boundary and while moving in the reverse direction within a gap adjacent said rear boundary.

Claim 10

The method of claim 7 further characterized in that said activating boundary capture is enabling a block-to-gap boundary capture mode at substantially the same time as said gap-to-block capture mode is enabled.

Claim 11

The method of claim 5 further comprising the following steps: prior to the moving the tape in the reverse direction, moving the tape in the forward direction across said block; capturing the rear boundary of said block; verifying that the gap immediately adjacent said rear boundary is at least as long as a predetermined nominal minimum interblock gap; and reversing the direction of said tape; and while said tape is moving in said reverse direction, activating boundary capture comprises enabling a gap-to-block capture mode when said position indicator indicates a position guaranteed to be within said gap provided the total relative error in tape position values accumulated subsequent to said forward motion capture of said rear boundary is within predetermined tolerance limits.

Claim 12

The method of claim 9 further characterized in that said enabling occurs about when said position indicator attains a value corresponding to the position value at the time of said forward motion rear boundary capture plus an offset corresponding to one half of a predetermined nominal minimum gap length.

Claim 13

The method of claim 9 further comprising: after capturing said rear boundary, enabling a block-to-gap capture mode; and capturing said front boundary.

Claim 14

The method of claim 9 further comprising the steps of: prior to the forward motion capture of said rear boundary, moving said tape in a forward direction within the gap immediately adjacent the front boundary of said block; while in said front gap enabling a gap-to-block capture mode; enabling a block-to-gap capture mode; capturing the front boundary of said block; capturing the rear boundary of said block; calculating the block length from the position values corresponding to the two forward motion captures; after said rearward motion capture of said rear boundary, traversing said block, and enabling a block-to-gap capture mode when the position indicator indicates a value corresponding to the value of said reverse motion capture of said rear boundary less the calculated length of said block and plus an offset corresponding to a predetermined tolerance; and capturing said front boundary.

Claim 15

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.

Claim 16

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.

Claim 17

The system of claim 13 wherein said boundary capture means includes means for capturing a gap-to-block boundary while said tape is moving in the rearward direction.

Claim 18

The system of claim 14 wherein said capture inhibit means includes means for selectively inhibiting gap-to-block boundary capture and means for selectively inhibiting block-to-gap capture, said capture inhibit means being adapted for use while said tape is moving in the rearward direction as well as in the forward direction during positioning.

Claim 19

The system of claim 13 wherein said boundary capture means includes means for capturing a block-to-gap boundary while said tape is moving in the rearward direction.

Claim 20

The system of claim 13 wherein said boundary capture means includes means for capturing a block-to-gap boundary while said tape is moving in the forward direction.

Claim 21

The system of claim 17 wherein said boundary capture means includes means for capturing a gap-to-block boundary while said tape is moving in the forward direction, and said controller means includes means for calculating the length of a block from a stored position value representing the forward motion capture of a gap-to-block boundary and a stored position value representing the next forward motion capture of a block-to-gap boundary.

Claim 22

The system of claim 17 further comprising gap verify means for verifying that a gap meets a predetermine nominal minimum interblock gap length, said gap verify means being adapted to determine whether a gap meets said nominal minimum gap length.