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Dual channel helical recorder
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Inventors: Zook, Christopher P.; Bordasch, Robert; Georgis, Steven P.; Atai-Azimi, Alireza; Pisciotta, Christopher; Haughland, Steve E.; Hughes, Timothy C.;
Assignee: Exabyte Corporation (Boulder, CO)
Primary Examiner: Psitos; Aristotelis
Assistant Examiner: Sheladia; Varsha V.
Attorney, Agent or Firm: Nixon & Vanderhye
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. In addition, a block written by a first write head (W1) and perceived as having been written as a bad block must be written by a second write head (W2) before that block is rewritten a predetermined number of times. |
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DETAILED DESCRIPTION OF THE DRAWINGS FIG.
1 shows drum and transport portions of a helical scan system 30 for recording digital information on magnetic tape 32.
The helical scan system 30 includes a tape transport 34 and a rotating drum 36.
The tape transport 34 includes a capstan 42 and two tape guides 44.
In conventional manner, the capstan 42 is rotated by an unillustrated capstan drive motor in order to move the tape 32 in a direction of tape travel indicated by arrows 46.
In the illustrated embodiment, the capstan 42 rotates to transport the tape 32 at a speed on the order of about one-half inch per second.
DRUM AND HEAD STRUCTURE The drum 36 is rotatable about drum axis 50.
The drum is rotated at a velocity of about 1800 rpm by an unillustrated drum motor.
An unillustrated tachometer detects rotations of the drum motor shaft, and hence of the drum, and produces a DRUM SYNC signal.
As shown in FIG.
2, drum axis 50, and hence drum 36, is angularly oriented with respect to the edges and direction of travel of the tape 32.
The drum 36 has a drum upper surface 52 and a drum lower surface 54, both of which are planar.
The drum axis 50 is orthogonal to both the drum upper surface 52 and the drum lower surface 54.
The drum 36 also has a peripheral surface 56 which wraps around the circumference of the drum 36.
The peripheral surface 56 of the drum 36 has two sets of heads mounted thereon, in particular a first set of heads comprising write heads W1 and W2 and a second set of heads comprising read heads R1 and R2.
In addition, the peripheral surface 56 of the drum 36 has a servo head S mounted thereon.
The heads W1, W2, R1, and R2 are mounted to generate helical stripes on the magnetic tape 32 in the manner shown in FIG.
6.
Heads W1 and W2 essentially simultaneously write first and second tracks of data, i.
e.
, tracks T1 and T2, respectively, on the tape 32.
Heads R1 and R2 are positioned to read tracks T1 and T2, respectively, 180 degrees after the tracks T1 and T2 are written.
In this respect, although FIG
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