Fujitsu M3097DG A.3 Bus Phases, Figure 4.2 Phase sequence, Table A.3 Method of driving the interface signal

Scanner Interface

Table A.3 Method of driving the interface signal

	OR connection	NON-OR connection
False	No signal is driven by any SCSI device.	The signal is driven false by a certain
	Signal status is made false by the	SCSI device (initiator or target), or is
	termination resistor circuits.	not driven by any SCSI device.
True	A SCSI device drives the signal true.

A.3 Bus Phases

The SCSI architecture includes the following eight distinct phases:

∙BUS FREE phase

∙ARBITRATION phase

∙SELECTION phase

∙RESELECTION phase

∙ COMMAND phase

∙ DATA phase

INFORMATION TRANSFER phase

∙ STATUS 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 transits to another.

Reset
		MESSAGE OUT
	SELECTION
		COMMAND
		DATA IN or
BUS FREE	ARBITRATION
		DATA OUT
			STATUS
	RESELECTION
		MESSAGE IN

The signal delay times for each bus phase are defined as follows:

Figure 4.2 Phase sequence

Appendix A-8