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SCSI Description
Quantum DLT 4000 Tape Drive
3-11
During normal operation, the BUS FREE phase is entered when the drive
releases the BSY signal. However, the BUS FREE phase can be entered following
the release of the SEL signal after a SELECTION or RESELECTION phase time-
out. BUS FREE might be entered unexpectedly. If, for example, an internal
hardware or firmware fault makes it unsafe for the tape drive to continue
operation without a full reset (similar to a power-up reset), or if ATN is asserted
or a bus parity error is detected during non-tape data transfers.
CAUTION
Any occurrence of a bus parity error (i.e., a single-bit error) should
be considered serious: it implies the possibility of undetected
double-bit error may exist on the bus. This may cause undetected
data corruption. On properly configured SCSI buses, parity errors
are extremely rare. If any are detected they should be addressed by
improving the configuration of the SCSI bus. A well-configured SCSI
bus in a normal environment should be virtually free of bus parity
errors.
Bus parity errors cause the tape drive to retry the operation, go to
the STATUS phase, or go to BUS FREE and prepare Sense Data.
Retrying of parity errors during Data Out Phase when writing is
normally not done, but can be enabled by changing the
EnaParErrRetry parameter in the VU EEROM Mode Page. This feature
is not enabled by default because of possible negative impact on
device performance (the data stream on writes cannot be pipelined
as well).
Initiators normally do not expect the BUS FREE phase to begin because of the
drive’s release of the BSY signal unless it has occurred after the detection of a
reset condition or after a drive has successfully transmitted or received one of
the following messages:
Messages Transmitted from Drive:
•
DISCONNECT
•
COMMAND COMPLETE
Summary of Contents for DLTtape DLT 4000
Page 1: ...DLT 4000 Tape Drive Product Manual November 10 2003 81 60043 04 ...
Page 5: ...USER MANUAL STATEMENTS FOR CLASS B EQUIPMENT continued ...
Page 6: ......
Page 24: ...About This Manual Quantum DLT 4000 Tape Drive xxiv ...
Page 62: ...Hardware Implementation 2 28 Quantum DLT 4000 Tape Drive ...
Page 100: ...Messages 4 12 Quantum DLT 4000 Tape Drive ...
Page 264: ...SCSI Commands 5 164 Quantum DLT 4000 Tape Drive ...
Page 274: ...Appendix B EEPROM Resident Bugcheck and Event Logs B 6 Quantum DLT 4000 Tape System ...
Page 280: ...Appendix C Updating the Firmware C 6 Quantum DLT 4000 Tape Drive ...
Page 298: ...Index Index 6 Quantum DLT4000 Tape Drive ...
Page 299: ......