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Messages
4-6
Quantum DLT 4000 Tape Drive
4.2.4 DISCONNECT Message (04h)
The DISCONNECT message is sent from the drive to inform the initiator that
the present connection is going to be broken (the drive plans to disconnect by
releasing the BSY signal) and a later reconnect will be required to complete the
current I/O process. The message does not cause the initiator to save the data
pointer. After sending the message, the drive goes to the BUS FREE phase by
releasing the BSY signal.
The DISCONNECT message can also be sent by the initiator to tell the drive to
suspend the current phase and disconnect from the bus. The drive’s response to
and its handling of a DISCONNECT message are based on when, in the I/O
process, the initiator introduces the DISCONNECT message. Table 4–4
summarizes the drive’s response.
Table 4–4 Drive Response to DISCONNECT Message
BUS Phase
Drive Response
SELECTION
The drive discards the DISCONNECT message and goes to BUS FREE.
COMMAND
The drive discards the DISCONNECT message and goes to BUS FREE. The
ATTENTION request is ignored while the Command Descriptor Block is fetched.
The drive does not switch to MESSAGE OUT until the current DMA completes.
DATA
The ATTENTION request is ignored while the current data transfer completes;
that is, the drive does not switch to MESSAGE OUT until after the current DMA
completes. The drive returns a MESSAGE REJECT message and responds with
CHECK CONDITION status, indicating the command aborted because of an
invalid message.
STATUS
The drive sends a MESSAGE REJECT message, then sends COMMAND
COMPLETE.
MESSAGE IN
The drive sends a MESSAGE REJECT message and switches to the BUS FREE
phase.
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: ......