Error Recovery
If
an error occurs while a Target is executing a queued command, the following error recovery
sequence is performed
to
ensure proper handling of any commands still in the queue:
1.
Target sends a Check Condition
status
to
the current Initiator.
2.
A Contingent Allegiance condition is established for the current Initiator. This means all
commands in
the
queue are suspended until the next command is received from
the
current
Initiator (normally a
REQUEST SENSE command). Commands received from other
Initiators will be queued normally.
3.
If
QErr=l
in the Control Mode Parameter Page
OAh
(refer
to
the
Mode Select and Mode
Sense commands), all commands in
the
queue are aborted upon receipt of a command
to
clearwhich clears
the
Contingent Allegiance condition. A Unit Attention condition with
an
Additional Sense Key
of
Tagged Commands Cleared by Another Initiator is established for
all other Initiators
that
had
commands in the-queue.
4.
Current Initiator sends
the
next command.
If
the next command is an untagged
REQUEST SENSE, it is'executed immediately by the Target.
lithe
next command is any
command other
than
an untagged REQUEST SENSE, error recovery is terminated and the
command is queued or rejected according to normal queuing procedures.
5.
The
Contingent Allegiance condition is removed, and any commands still in the queue are
executed by
the
Target in a normal manner.
Synchronized
Spindle
Operation
Synchronized spindle operation (Master or Slave modes) is enabled via Mode Page 04R. Refer
to
Table
2-2
(Chapter 2), and the Mode Sense/Mode Select command information (Appendix
A), for more details about implementing these functions.
Assembly
Descriptions
The
assemblies in
the
disk drive include the head/disk assembly (RDA) and the drive
electronics/controller printed-circuit assembly
(PCA). The sealed RDA contains
the
mechanical and electromechanical assemblies of the disk drive. The drive electronics/controller
PCA
provides the SCSI interface and all electronic control over the RDA. The following
paragraphs describe
the
major functional components of each assembly.
Head/Disk
Assembly
The head/disk assembly (RDA) contains disks, heads,
an
actuator
assembly, head interface
circuits, atmospheric controls, vibration isolators, and a spindle assembly. A stainless steel
baseplate and cover provide
the
supporting structure for these parts. The entire assembly is
sealed and is not field repairable.
Disks
The disks are 3.5-inch (95 mm) diameter aluminum substrates with sputtered thin-film
surfaces.
Data
is stored on
both
surfaces of all disks except for one surface reserved for servo
information.
3·6 Product Features DRAFT
1/18/93 08:58
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