Scsi Bus Conditions; Attention Condition - Quantum DLT 8000 Product Manual

SCSI Description
3.6

SCSI Bus Conditions

The SCSI bus has two asynchronous conditions: Attention and Reset.

3.6.1 Attention Condition

The attention condition informs a drive that an initiator has a message ready. The drive
gets the message by performing a MESSAGE OUT phase. The attention condition
requires the following timing:
The initiator creates the attention condition by asserting ATN at any time
except during the ARBITRATION or BUS FREE phases.
The initiator negates the ATN signal at least two deskew delays before
asserting the ACK signal while transferring the last byte of the message.
If the drive detects that the initiator failed to meet this requirement, then
the drive goes to BUS FREE.
Before transition to a new bus phase, the initiator asserts the ATN signal,
then waits at least two deskew delays before negating the ACK signal for
the last byte transferred in the current bus phase. Asserting the ATN signal
later cannot be honored until a later bus phase and then cannot result in
the expected action.
The drive responds with MESSAGE OUT as described in the following table.
3-26 Quantum DLT 8000 Tape System