Abstract: Methods and systems for sensing a position of a transducer head with respect to a storage medium. One method includes generating a read signal from a servo track stored on a magnetic storage medium. The servo track includes servo frames of magnetic flux transitions forming detectable servo marks, the servo marks forming a tone field of repeating servo marks oriented at a first azimuth angle and a mid-frame synchronization mark incorporated within the tone field, wherein the tone field provides a metric reference for dimensional measurements between features within the servo frame(s). The number of servo marks in the tone field of each servo frame along a longitudinal direction of the servo track before the mid-frame synchronization mark and after the mid-frame synchronization mark varies with lateral position.

Abstract: Methods and systems for sensing a position of a transducer head with respect to a storage medium. One method includes generating a read signal from a servo track stored on a magnetic storage medium. The servo track includes servo frames of magnetic flux transitions forming detectable servo marks, the servo marks forming a tone field of repeating servo marks oriented at a first azimuth angle and a mid-frame synchronization mark incorporated within the tone field, wherein the tone field provides a metric reference for dimensional measurements between features within the servo frame(s). The number of servo marks in the tone field of each servo frame along a longitudinal direction of the servo track before the mid-frame synchronization mark and after the mid-frame synchronization mark varies with lateral position.

Abstract: Methods and systems for sensing a position of a transducer head with respect to a storage medium. One method includes generating a read signal from a servo track stored on a magnetic storage medium. The servo track includes servo frames of magnetic flux transitions forming detectable servo marks, the servo marks forming a tone field of repeating servo marks oriented at a first azimuth angle and a mid-frame synchronization mark incorporated within the tone field, wherein the tone field provides a metric reference for dimensional measurements between features within the servo frame(s). The number of servo marks in the tone field of each servo frame along a longitudinal direction of the servo track before the mid-frame synchronization mark and after the mid-frame synchronization mark varies with lateral position.

Abstract: Methods and systems for sensing a position of a transducer head with respect to a storage medium. One method includes generating a read signal from a servo track stored on a magnetic storage medium. The servo track includes servo frames of magnetic flux transitions forming detectable servo marks, the servo marks forming a tone field of repeating servo marks oriented at a first azimuth angle and a mid-frame synchronization mark incorporated within the tone field, wherein the tone field provides a metric reference for dimensional measurements between features within the servo frame(s). The number of servo marks in the tone field of each servo frame along a longitudinal direction of the servo track before the mid-frame synchronization mark and after the mid-frame synchronization mark varies with lateral position.

Abstract: A helical scan tape recorder (30) comprises a rotatable scanner (85) upon which is mounted a first set of plural transducing heads (W1, W3) and a second set of transducing heads (W2, W4). A transport system transports magnetic tape (31) proximate the rotatable scanner in a manner so that information is transduced by at least one of the transducing heads during a revolution of the scanner. The sets of transducing heads are so mounted on the scanner with respect to azimuthal orientation of the transducing heads that all tracks transduced by the transducing heads have a desired width regardless of an error in physical distance separating the sets of transducing heads. In one aspect, the first set of plural transducing heads comprises a first head (W1) and a third head (W3), and the second set of plural transducing heads comprises a second head (W2) and a fourth head (W4).

Abstract: In a helical scan recording system, magnetic tape (31) is transported by a tape transport (98) proximate a rotating scanner (85). The scanner has a pair of read heads (82) mounted thereon, e.g., a first read head and a second read head, which travel in a helical direction on the magnetic tape in view of the transport of the tape and rotation of the scanner. A synchronization detection system (38) determines a first synchronization mark detection time at which a first synchronization mark is read by the first read head from the first track, and a second synchronization mark detection time at which a synchronization mark read by the second read head from the second track. A position error signal generator (100) develops a position error signal (PES) based upon a difference between the first synchronization mark detection time and the second synchronization mark detection time.

Abstract: A helical scan tape recorder (30) comprises a rotatable scanner (85) upon which is mounted a first set of plural transducing heads (W1, W3) and a second set of transducing heads (W2, W4). A transport system transports magnetic tape (31) proximate the rotatable scanner in a manner so that information is transduced by at least one of the transducing heads during a revolution of the scanner. The sets of transducing heads are so mounted on the scanner with respect to azimuthal orientation of the transducing heads that all tracks transduced by the transducing heads have a desired width regardless of an error in physical distance separating the sets of transducing heads. In one aspect, the first set of plural transducing heads comprises a first head (W1) and a third head (W3), and the second set of plural transducing heads comprises a second head (W2) and a fourth head (W4).

Abstract: In a helical scan recording system, magnetic tape (31) is transported by a tape transport (98) proximate a rotating scanner (85). The scanner has a pair of read heads (82) mounted thereon, e.g., a first read head and a second read head, which travel in a helical direction on the magnetic tape in view of the transport of the tape and rotation of the scanner. A synchronization detection system (38) determines a first synchronization mark detection time at which a first synchronization mark is read by the first read head from the first track, and a second synchronization mark detection time at which a synchronization mark read by the second read head from the second track. A position error signal generator (100) develops a position error signal (PES) based upon a difference between the first synchronization mark detection time and the second synchronization mark detection time.

Abstract: In a method of calibrating a helical scan magnetic tape drive, a dual scan calibration tape having a calibration stripe is loaded into the tape drive. As a head traverses differing paths along the calibration stripe, a series of calibration signal waveforms is obtained. For each calibration signal waveform in the series, a voltage measurement is made at a predetermined position within each waveform. A maximum one of the voltage measurements is used to generate a measured overlap scale factor (MOV) indicative of an overlap of the read head relative to the calibration stripe. As a subsequent calibration stripe on the calibration tape is read in a dual scan calibration mode, the measured overlap scale factor is utilized to generate a track position error vector. The track position error vector is used to adjust a tape path guide of the tape drive.

Abstract: Methods of calibrating a helical scan recorder include transporting a storage media past a drum at a controlled linear velocity and recording tracks on the media using a write head. During a read-after-write operation, servo signals recorded on the tracks are read. The servo signals from the tracks are used to determine an axial offset variance of the write head and a read head on the drum. In one mode, calibration is achieved for a first helical scan recorder which does not have a capstan, by installing a drum of the recorder in a second helical scan recorder, using the second recorder to record servo signals on two tracks, reading the servo signals from those two tracks in the second recorder, using the servo signals to determine axial offset variance, and storing a value indicative of axial offset variance in a memory of the first recorder. The axial offset variance is used in a write splice operation and, in one mode, to determine linear velocity of the media.

Abstract: Write splicing for a helical scan tape drive (30) involves, upon occurrence of a predetermined condition such as a buffer low condition, recording an indication of a tape transport transition (ITTT) on tape (31) and then recording dummy helical stripes (DSd1-DSdn) having deviant form as the magnetic tape is decelerated to a stop. After the predetermined condition is overcome, further deviant, dummy stripes (DSa1-DSan) are recorded as the tape is accelerated back to nominal tape transport speed. At the nominal tape transport speed, non-deviant stripes (S2) containing user data are again recorded on tape. A distance separating a first set of stripes ?S1! (recorded prior to the occurrence of the predetermined condition) and a second set of stripes ?S2! (recorded upon again attaining the nominal tape transport speed) is an integer multiple of the track pitch (P) of a non-deviant stripe. The write splice is thus performed without reversing the direction of tape transport.

Abstract: Methods and apparatus are provided for determining a servo offset value and a take-up reel velocity for imparting a desired linear velocity to tape in a helical scan recording system (20). The helical scan recorder system records information on a magnetic tape (22), the magnetic tape being transported between a supply reel (24) and a take-up reel (26) in the helical scan recorder through a tape path, which tape path includes at least a partial wrapping of the tape around a drum (30) of the helical scan recorder. The methods include moving the tape from the supply reel to the take-up reel whereby the tape travels a predetermined displacement; rewinding the tape by the tape extraction displacement and determining an angular rewind displacement of the take-up reel; and using the determined displacements to ascertain parameters including a desired velocity of the take-up reel.

Abstract: Methods of calibrating a helical scan recorder include transporting a storage media past a drum at a controlled linear velocity and recording tracks on the media using a write head. During a read-after-write operation, servo signals recorded on the track; are read. The servo signals from the tracks are used to determine an axial offset variance of the write head and a read head on the drum. In one mode, calibration is achieved for a first helical scan recorder which does not have a capstan, by installing a drum of the recorder in a second helical scan recorder, using the second recorder to record servo signals on two tracks, reading the servo signals from those two tracks, second recorder, using the servo signals to determine axial offset variance, and storing a value indicative of axial offset variance in a memory of the first recorder. The axial offset variance is used in a write splice operation and, in one mode, to determine linear velocity of the media.

Abstract: Methods and apparatus are provided for determining a servo offset value and a take-up reel velocity for imparting a desired linear velocity to tape in a helical scan recording system (20). The helical scan recorder system records information on a magnetic tape (22), the magnetic tape being transported between a supply reel (24) and a take-up reel (26) in the helical scan recorder through a tape path, which tape path includes at least a partial wrapping of the tape around a drum (30) of the helical scan recorder. The methods include moving the tape from the supply reel to the take-up reel whereby the tape travels a predetermined displacement; rewinding the tape by the tape extraction displacement and determining an angular rewind displacement of the take-up reel; and using the determined displacements to ascertain parameters including a desired velocity of the take-up reel.

Abstract: In a helical scan system for recording information on a storage media in a series of helical tracks, servo information written on the tracks is used to control linear velocity of the media during a write operation. Helical scan system includes a rotating drum upon which write heads and read heads circumferentially are mounted. The write heads and the read heads are positioned on the drum so that during a drum revolution a read head reads servo information recorded on a track at least 1.5 track pitches upstream from the most recently recorded track. A servo controller analyzes, during the recording operation, servo information read back by the read head subsequent to recording thereof by write head. Servo controller uses the servo information read by the read head to generate a signal for application to a motor for controlling linear velocity of the media during the write operation.

Abstract: A helical scan system (10) determines whether a medium is a non-native formatted medium and controls operating parameters (e.g., tape speed) so that a non-native formatted medium can be read without resort to embedded servo information in the non-native medium. The helical scan system reads the medium in a manner to obtain format-indicative information therefrom, and then determines whether the medium is non-native formatted. If the medium is non-native formatted, a controller determines operating parameters required by the system to read the non-native formatted medium and generates signals corresponding to the required operating parameters. The medium is preferably read in a slow speed mode in order to obtain format-indicative information therefrom, and block header information obtained from the medium is analyzed to determine whether the medium is non-native formatted.

Abstract: A helical drive system (10) reads tracks (18) on a storage medium (12), including tracks which appear as distorted tracks. Each track (18) comprises a plurality of blocks of data, with each block having unique block-identifying information. A read head (16C) traverses predetermined original azimuthal paths (P0) across the storage medium (12) for reading the blocks recorded along each of the original azimuthal paths (P0). A controller (50) uses the block-identifying information to determine whether any blocks expected to be read during the traversal of the original azimuthal paths (P0) were not read. If expected blocks were not read, the controller (50) rewinds or otherwise reverses the direction of travel of the storage medium (12); sends a signal to a tape transport drive (81) to slow the speed of the medium (12); and, directs that the medium (12) be re-read at a slower tape reread speed. During the slow re-read attempt, the read head (16C) traverses modified azimuthal paths (P1, P2, P3 , . . .

Abstract: A dual channel helical scan recording system (30) includes a rotating dum (36) having sets of heads (W1, W2) (R1, R2) mounted on its peripheral surface (56). A set of write heads (W1, W2) is situated on an opposite side of the drum (36) from a set of read heads (R1, R2). The write heads (W1, W2) simultaneously write two adjaent tracks (T1, T2), which are read for verification 180 detrees later by corresponding read heads (R1, R2). The heads (W1, W2, R1, R2) are strategically mounted on the drum (36) with respect to angular and axial placement, and have selected head widths and azimuthal angles. Should a block of data (317) written to tape (32) be determined, during readback, to be bad block, that bad block is subsequently rewritten on the tape (32) in the course of writing good blocks and amongst other good blocks. The rewritten block is recorded at a row position on the tape which is sufficiently displaced from the row position of a previous writing to avoid media defects occuring on the tape.

Abstract: In a servo tracking method and apparatus, a servo head (S) of a helical scan recorder (30) endeavors to travel equidistant between two servo signal-bearing stripes recorded on the tape (32). The recorder (30) determines a reference-crossing time at which the servo head (S) begins to cross a horizontal reference line (606) drawn with respect to the beginning of a stripe on the tape (32). The servo head (S) samples the amplitude of a servo signal provided on the tape (32) at a plurality of predetermined times after the reference-crossing time. A servo tracking circuit (175) uses the amplitude of the servo signal at the predetermined sampling times to determine how to adjust the position of said head (S) relative to the pitch of said stripe.

Abstract: Method and apparatus are provided for developing a digital timing signal indicative of when a head of a helical scan recorder (30) is positioned over a recorded stripe on magnetic tape (32). The method involves rotating a drum (36) upon which a head is mounted while the magnetic tape (32) is transported past the drum at a speed greater than the nominal speed at which stripes were recorded on the tape. Given the geometry of the system and format of the tape, the head is eventually able to recognize a pattern of digital data. The timing of the recognition of the pattern of digital data is used to determine the precise time, relative to each rotation of the drum (36), that the head ceases to traverse a stripe and the precise time during each rotation of the drum that the head begins to traverse a stripe. The determination of the edges of the digital timing signal is repeated upon every rotation of the drum (36).