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Cartridge Load Algorithm to Harden Tape Tension Profile Computations

IP.com Disclosure Number: IPCOM000110052D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 3 page(s) / 119K

Publishing Venue

IBM

Related People

Dunn, EC: AUTHOR [+5]

Abstract

Increased "tape-slip" detection is provided by this invention to significantly reduce the risks of incorrectly initializing drive tension tables. These tension tables profile the tape and are the basis for drive motor control and media-type determination.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Cartridge Load Algorithm to Harden Tape Tension Profile Computations

       Increased "tape-slip" detection is provided by this
invention to significantly reduce the risks of incorrectly
initializing drive tension tables.  These tension tables profile the
tape and are the basis for drive motor control and media-type
determination.

      At the time a cartridge is loaded into the 3490E tape drive, an
Accumulate Tach Line Count Routine is initiated during the period of
time it takes for tape to be wound off of the file reel onto the
machine reel.  Roughly 6 machine reel tach line counts are expended
to load a tape to a starting point known as Physical Beginning of
Tape (PBOT).  The machine reel has coarse tach line resolution
whereas the file reel has fine tach line resolution.  During 5 of the
6 machine reel tach periods, the file reel tach line counts are
accumulated.
This accumulated count is used to:
*    Define maximum tape length
*    Define the End of Tape distance (relative tach count)
*    Select the appropriate Tension Table from a set of 8

      Once at PBOT, two tests are initiated to detect tension
problems (ILS Test):
1.   A velocity test is initiated by the drive to ramp tape speed up
and down to 140% of maximum acceleration.  Failure of this test is an
indication of Inter-Layer Slip which generates a drive check code of
'15'X.  Internal error recovery is attempted on this error condition.
2.   During the velocity test, tension is monitored by means of a
pneumatic tension transducer.  Major tension errors cause permanent
load errors (CHK44) to be reported which are not recovered
internally.  Transient tension errors create a drive check code of
'15'x (CHK15) which initiates internal error recovery.

      Internal error recovery in response to a drive CHK15 is a tape
refresh.  A tape refresh consists of a high-speed locate out to the
End of Tape (EOT), followed by a rewind to PBOT.  This action evens
out tension and wrap alignment across the length of tape.  During the
time tape is moving to PBOT, the drive is making computations to
determine which drive tension table to select and the type of media
which is being mounted.  Any tape slip or tension variation during
this key period of time is not detected or compensated for.  This can
result in an unoptimized initialization of the Drive Tension Table.
An accurate Drive Tension Table is critical to data processing, since
it defines the tape length (EOT) and the mot...