Head-tape alignment apparatus with a tape edge find operation

In apparatus for aligning a read-write head over previously written data on a tape in a tape drive, the combination comprising:

• control means for a tape drive for locating one edge of the tape by providing a sequence of control outputs for positioning the read-write head beyond the edge of the tape, writing a signal
• to the read-write head, attempting to read a signal from the tape using the read-write head, and stepping the read-write head toward the tape and repeating said write, read and step sequence until a
• data signal from the tape is
• detected with a read circuit, said control means providing a control output for moving said head a fixed distance from said edge, to a selected data track on the tape for aligning said head over said data track edge, and
• a threshold circuit responsive to said control means for setting an amplitude level which is a set threshold level for edge find at which the read data output is passed from a head read gap of the tape drive, said set threshold level for edge find corresponding to a read data output amplitude when only a small portion of the head read gap is on the tape during an edge find operation to increase the edge find accuracy, said level being increased by said control means to a set threshold level for a normal tape during a data read-out operation.

In apparatus for electronically aligning a read-write head over previously written data on a tape in a tape drive, the combination comprising:

• control means for a tape drive for locating one edge of the tape by providing a sequence of control outputs for positioning a read-write head below the edge of the tape, writing a signal to the read-write head , attempting to read a signal from the tape using the read-write head, and stepping the read-write head up and repeating said write, read and step sequence until a digital signal
• from the tape is detected with a read circuit, providing a control output for moving said head a fixed distance to a selected data track previously recorded on the tape for aligning said head over said data track edge, and
• said control means providing a write data output to write a data stripe on a selected segment of the tape for use in locating the edge of the tape during an edge find operation on a write protected tape,
• a sensor to indicate to said control unit if the tape is write protected and if write protected said control means providing a different sequence of control outputs to locate the edge of said tape,
• a threshold circuit for setting an amplitude level which is a set threshold level for edge find at which the read data output can be passed from a head read gap of the tape drive, said set threshold level for edge find corresponding to a read output amplitude when only a small portion of the read head gap is on the tape during an edge find operation, to increase the edge find accuracy and subsequent reliability of reading out data from said tape.

In apparatus for aligning a read-write head over previously written data on a tape in a tape drive, the combination comprising:

• control means for a tape drive for locating one edge of a tape by providing a sequence of control outputs to said tape drive for positioning a read-write head of the tape drive beyond the edge of the tape, writing a signal to the read-write head, attempting to read a signal from the tape using the read-write head, stepping the read-write head toward the tape and repeating said write, read and step sequence until a data signal from the tape is detected with a read circuit,
• wherein in locating said one edge said sequence of control outputs first perform a coarse edge find followed by a precise edge find,
• said coarse edge find including a binary search in which data is written on a segment of the tape, attempted to be read and if a signal is not found the head is moved with the stepping interval each time becoming smaller by a factor of two,
• said control means providing a control output for moving said head a fixed distance from said one edge to a selected data track on said tape for aligning said head over said data track.

In apparatus for aligning a read-write head over previously written data on a tape in a tape drive, the combination comprising:

• control means for a tape drive for locating one edge of a tape by providing a sequence of control outputs to said tape drive for positioning a read-write head of the tape drive beyond the edge of the tape, writing a signal to the read-write head, attempting to read a signal from the tape using the read-write head, stepping the read-write head toward the tape and repeating said write, read and step sequence until a data signal from the tape is detected with a read circuit,
• said control outputs being sequenced so that after the edge is found if no data stripe is present on the tape said control means provides a write data output to write a data stripe on a selected segment of the tape for use locating the edge of the tape during an edge find operation of a write-protected tape,
• said control means providing a control output for moving said head a fixed distance from said one edge to a selected data track on said tape for aligning said head over said data track, and
• a sensor to indicate to said control unit if the tape is write-protected and if write-protected said control means providing a different sequence of control outputs to locate the edge of the tape.