Scsi-Bus Phase Sequences - Tandberg Data SLR7-140 PROGRAMMER Manual

Tandberg Data
3.1.2.4. Message-In/Out Phases
The MESSAGE-IN phase is used by the Drive to request
message(s) be sent from the Drive to the Initiator.
The MESSAGE-OUT phase is used by the Drive to request
message(s) be sent from the Initiator to the Drive.
3.2.

SCSI-bus Phase Sequences

The order in which phases are used on the SCSI-bus
follows a prescribed
however can abort any phase and is always followed by
the BUS FREE phase.
The sequences allowed by the SCSI standard are shown in
the figure below. The normal progression is:
From the BUS FREE phase to ARBITRATION
From ARBITRATION to SELECTION or RESELECTION
and
From SELECTION or RESELECTION to one or more of the
information transfer phases (COMMAND, DATA-IN/OUT,
STATUS, or MESSAGE-IN/OUT)
Reset or protocol error
BUS FREE
Figure 3-1:
3-3 Tandberg SLR Product Line SCSI Functional Specifications
sequence. The
SELECTION
ARBITRATION
RESELECTION
Phase Sequencing
Logical Characteristics
RESET condition
MESSAGE OUT
COMMAND
DATA IN
DATA OUT
STATUS
MESSAGE IN