Scsi Bus Operations; Bus Phases - Sun Microsystems storagetek sl500 Reference Manual

3
C H A P T E R

SCSI Bus Operations

This chapter describes the seven elements that SCSI uses for controlling the
interface, transferring data, issuing commands, and returning status for the SL500
library:

Bus phases

■
Bus signals
■
Bus conditions
■
Pointers
■
Messages
■
Commands
■
Status byte
■
Bus Phases
The SCSI bus uses eight states, called bus phases, to establish and control
connections between the initiator and the target:
Bus Free
■
Arbitration
■
Selection
■
Reselection
■
Information Transfer phases:
Message (in or out)
■
Command
■
Data (in or out)
■
Status
■
Each bus phase is governed by a predetermined set of rules established by SCSI.
Note – The SCSI bus can only be in one phase at a time.
96122 • Revision: F 15