Table 4-4 Method of driving the interface signal

 

OR connection

NON_OR connection

 

 

 

False

No signal is driven by any

The signal is driven false by

 

SCSI device. Signal status is

a certain SCSI device

 

made false by the termination

(initiator or target), or is not

 

resistor circuits.

driven by any SCSI device

True

A SCSI device drives the signal true.

4.3 Bus Phases

The SCSI architecture includes the following eight distinct phases:

BUS FREE phase

 

 

ARBITRATION phase

 

 

SELECTION phase

}

 

COMMAND phase

 

DATA phase

 

STATUS phase

INFORMATION TRANSFER phase

 

MESSAGE phase

 

The SCSI bus can never be in more than one phase at any given time.

The following diagram shows how each phase transmits to another.

Reset

 

 

 

 

MESSAGE OUT

 

SELECTION

 

 

 

COMMAND

BUS FREE

ARBITRATION

DATA IN or

 

 

DATA OUT

 

 

STATUS

MESSAGE IN

Figure 4-2 Phase sequence

4-9

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Image 37
Fujitsu 600C manual Bus Phases, Method of driving the interface signal, Or connection Nonor connection