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SCSI Description
Quantum DLT 8000 Tape System
3-11
3.5
SCSI Bus Phases
The SCSI architecture includes eight distinct phases:
BUS FREE phase
ARBITRATION phase
SELECTION phase
RESELECTION phase
COMMAND phase
DATA phases (In/Out)
STATUS phase
MESSAGE phases (In/Out)
The last four phases are called the “information transfer phases.”
The SCSI bus can never be in more than one phase at any given time. In the following
descriptions, signals that are not mentioned are not asserted.
3.5.1 BUS FREE Phase
The BUS FREE phase indicates that there is no current I/O process and that the SCSI
bus is available for a connection.
SCSI devices detect the BUS FREE phase after the SEL and BSY signals are both false
for at least one bus settle delay.
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.
Summary of Contents for DLTtape DLT 8000
Page 1: ...DLTTM 8000 Tape System Product Manual Nov 10 2003 81 60118 06...
Page 5: ...USER MANUAL STATEMENTS FOR CLASS B EQUIPMENT continued...
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Page 26: ...Table of Contents xxiv Quantum DLT 8000 Tape System...
Page 36: ...About This Manual Quantum DLT 8000 Tape System xxxii...
Page 54: ...General Description and Specifications 1 18 Quantum DLT 8000 Tape System...
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Page 376: ...Appendix A Definition of Vendor Unique Sense Data Information A 4 Quantum DLT 8000 Tape System...
Page 386: ...Appendix C Updating the Firmware C 6 Quantum DLT 8000 Tape System...
Page 396: ...Appendix E Visual Inspection Procedure for DLTtape Cartridges E 8 Quantum DLT 8000 Tape System...
Page 406: ...Appendix G DLT 7000 Emulation Feature G 8 Quantum DLT 8000 Tape System...
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