Specifications

24 ST43401N/ND and ST43402ND Reference Manual, Rev. C
Table 8. SCSI bus phase descriptions
Phase Description
Bus Free No SCSI device asserts Busy or Select for at least one bus
settle delay.
Arbitration Allows one SCSI device to gain access to the bus based on its
priority ID bit.
Selection Allows an initiator to select a target. The I/O line must not be
asserted in this phase.
Reselection Allows a target to reconnect to an initiator so it can continue an
operation started by an initiator but suspended by the target
before it was complete. The I/O line must be asserted during this
phase.
Command Allows the target to request command information from the
initiator.
Data The Data In phase allows the target to request that data be sent
to the initiator from the target.
The Data Out phase allows the target to request that data be
sent from the initiator to the target.
Status Allows the target to request that status information be sent from
the target to the initiator.
Message The Message In phase allows the target to request that mes-
sages be sent to the initiator from the target.
The Message Out phase allows the target to request that
messages be sent from the initiator to the target. The target can
invoke this phase at its convenience in response to an Attention
signal created by the initiator.