Reselection Phase - Quantum DLT 8000 Product Manual

Note that the initiator will release the SEL signal and may change the
DATA BUS no less than two deskew delays after it detects that the BSY
signal is true. The drive waits until the SEL signal is false before asserting
the REQ signal to enter an information transfer phase. Other signals (e.g.,
MSG, C/D) may also be asserted.
Selection Time-Out
Two optional time-out procedures are specified for clearing the SCSI bus if the
initiator waits a minimum of a selection time-out delay and there has been no
BSY signal response from the drive.
1. The initiator asserts the RST signal.
2. The initiator follows these steps:
a) Continues asserting the SEL and ATN signals and releases the DATA
BUS.
b) If it has not detected the BSY signal to be true after at least a selection
abort time plus two deskew delays, the drive releases the SEL and ATN
signals, allowing the SCSI bus to go to the BUS FREE phase.
When responding to selection, SCSI devices ensure that the selection was still
valid within a selection abort time of their assertion of the BSY signal. Failure
to comply with the requirement could result in an improper selection.

3.5.4 RESELECTION Phase

RESELECTION is an optional phase that allows a drive to reconnect to an initiator to
continue an operation that was previously started by the initiator but was suspended by
the drive.
The initiator determines that it is reselected when the SEL and I/O signals and its SCSI
ID bit are true, and the BSY signal is false for at least one bus settle delay.
Reselection Sequence
The drive:
1. Upon completing the ARBITRATION phase, asserts both the BSY and SEL
signals.
2. Delays at least one bus clear delay plus one bus settle delay.
3. Asserts the I/O signal.
Quantum DLT 8000 Tape System
SCSI Description
3-15