Browse Prior Art Database

Optical Media Unload Control

IP.com Disclosure Number: IPCOM000099852D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 4 page(s) / 171K

Publishing Venue

IBM

Related People

Kulakowski, JE: AUTHOR [+2]

Abstract

Removable optical disk media and optical disk drives have a set of unique characteristics that make the interaction between the personal computer system user and the hardware/software system differ greatly from the user interaction with a system having removable flexible magnetic disks. The interaction takes place most often in an environment where the multi-tasking operating system is managing the system resources and the optical disk drives are attached to the personal computer via the Small Computer System Interface (SCSI) supported by device driver code provided by the optical disk vendor.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 33% of the total text.

Optical Media Unload Control

       Removable optical disk media and optical disk drives have
a set of unique characteristics that make the interaction between the
personal computer system user and the hardware/software system differ
greatly from the user interaction with a system having removable
flexible magnetic disks.  The interaction takes place most often in
an environment where the multi-tasking operating system is managing
the system resources and the optical disk drives are attached to the
personal computer via the Small Computer System Interface (SCSI)
supported by device driver code provided by the optical disk vendor.
The large capacity removable characteristics of the media and drive
and the use of the SCSI attachment, with much of the error recovery
and disk formatting function outboard in the drive controller,
require mechanisms to manage media removal requests by the user.
This special management of media removal is needed during such times
as in the midst of command execution, during the reassignment of the
defective sectors to alternate sectors, during the update of the
volume directory, and during the update of user application data base
indices and data.  Media removal at inappropriate times could cause
the loss of any of the control structures which could cause the loss
of user data.

      The management of media removal is implemented through the use
of the SCSI command to prevent media, the drive indicator light, and
messages to the system user/operator. These mechanisms can be used to
provide a comprehensive management for removable media.

      FUNCTIONAL ELEMENTS The functional elements and their use to
manage media removal are described in the following text and consist
of (1) a SCSI Prevent/Allow Medium Removal command, (2) a Busy
indicator LED, (3) an Unload command, and (4) an Eject button.

      Prevent/Allow Medium Removal Command The Prevent/Allow Medium
Removal command definition is as follows:
                                   BIT
          7      6      5      4      3      2      1      0
BYTE 0                 COMMAND CODE = 1Eh
BYTE 1       LUN               Rsvd = 0
BYTE 2                 Rsvd = 0
BYTE 3                 Rsvd = 0
BYTE 4                 Rsvd = 0 Prvnt
BYTE 5   VU = 0            RSVD = 0              FLAG LINK

      The Prevent/Allow Medium Removal command requests that the
target enable or disable the removal of the medium in the logical
unit.

      A prevent bit of one shall inhibit mechanisms that normally
allow removal of the medium.  A prevent bit of zero shall allow
removal of the medium.

      This prevention of medium removal condition shall terminate
upon receipt of a Prevent/Allow Medium Removal command with the
prevent bit set to zero, or by the receipt o...