Extended SDTR Message
Target Error Conditions
The SDTR (SynChronous Data Transfer Request) message type will
only be accepted prior to the
Command phase, and only prior
to
the
first
Command phase in a linked command set. At any other time
it
will be treated as an illegal message type. If the negotiation process
is
started
by
the Initiator, the drive will respond with its SDTR message.
If
the Initiate SDTR Message Option
is
enabled, the drive will initiate
an
SDTR message
a.t
Power On and Reset.
Under some error conditions
the
Target may proceed
to
the
Bus Free phase without
terminating
the
command (i.e. no Disconnect
or
Command Complete message sent
to
the
host). In this case,
the
Target will not
attempt
to re-connect with
the
Initiator.
The
Initiator
should consider this as a catastrophic error. Information regarding
the
cause
of
this abnormal
response can be recovered by
the
Initiator with
the
REQUEST SENSE command.
Message Out Phase Parity Error
If
parity checking is enabled and a message out parity error is detected
the
disk drive will
abort
the
command
in
process and set
the
sense key
to
Aborted Command with
the
sense
code set
to
Parity Error. If a valid
LUN
has been received in an identify or in
the
CDB, and
status
phase has not yet begun, then
the
command will be terminated with a Check Condition
status; otherwise,
the
Target will go the
the
Bus Free
state.
Command
or
Data Out Phase Parity Error
If
parity checking is enabled and a Command or
Data
Out
phase parity error
is
detected then
disk drive will
terminate
the
command in process with a Check Condition status.
The
sense
information will have the sense key set
to
Aborted Command with
the
sense code set
to
Parity
Error.
Illegal Messages
If
an illegal or unexpected message out is received from
the
Initiator,
the
disk drive will
abort
the
command in process and set
the
sense key
to
Aborted Command with
the
sense code set to
Inappropriate/megal Message.
If
a valid LUN has been received
in
an identify or in
the
CDB,
and
the
status
phase has not yet begun, then
the
command will be terminated with a Check
Condition status; otherwise
the
Target will go
to
the
BUS
FREE
phase.
Reselection Timeout
If
the
Target
attempts
to reselect
the
Initiator
and
the
Initiator does not respond within a
Selection Timeout Delay,
the
Target will
attempt
to
reselect a second time.
If
the
second
attempt
fails,
the
Target will
abort
the command
in
process
and
make no further
attempts
to
reselect
the
host.
The
sense information will be set with a sense key of Hardware Error and a
sense code
of
Select/Reselect Failed.
4·8
SCSI
Interface
DRAFT
1/18/93 09:58
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