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C156-E097-01EN 7 - 1
CHAPTER 7 SCSI BUS
7.1 System Configuration
7.2 Interface Signal Definition
7.3 Electrical Requirements
7.4 Timing Rule
7.5 Bus Phases
7.6 Bus Conditions
7.7 Bus Sequence
This chapter describes the structure of the SCSI bus, electrical conditions, interface protocol and their
operations.
IMPORTANT
The ODD operates on the SCSI bus as a TARG. In this chapter, the
ODD is represented as "TARG" except where some special distinction
must be made.
7.1 System Configuration
Up to eight SCSI divices can be connected to the SCSI bus. Figure 7.1 shows sample system
configurations. Communication on the SCSI bus is allowed between only two SCSI divices, an
initiator (INIT) and a target (TARG), at any given time.
In the configured system, any combination is allowed for an SCSI device to work as an INIT and
as a TARG. Also, there may be an SCSI device that works as both an INIT and a TARG.
A unique address (SCSI ID) is assigned to each SCSI device. The SCSI ID corresponds to one
bit of the SCSI data bus. The INIT designates an I/O device connected to the TARG by its
logical unit number (LUN).
The SCSI ID of the ODD can be selectable among #0 to #7, but the LUN is fixed to #0.