Disconnect Message (04H); Table 4–4 Drive Response To Disconnect Message - Quantum DLT 8000 Product Manual

Messages

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.
BUS Phase
SELECTION
COMMAND
DATA
STATUS
MESSAGE IN
4-6
Table 4–4 Drive Response to DISCONNECT Message
Drive Response
The drive discards the DISCONNECT message and goes to BUS FREE.
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.
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.
The drive sends a MESSAGE REJECT message, then sends COMMAND
COMPLETE.
The drive sends a MESSAGE REJECT message and switches to the BUS FREE
phase.
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