Bus Phase Sequence; Bus Phase Sequence With Information Units Disabled; Figure 1.42 Reset Condition - Fujitsu MBA3073 SERIES Technical Manual

1.8

Bus Phase Sequence

1.8.1

Bus Phase Sequence with Information Units Disabled

The SCSI bus phases are switched in the specific sequence depending on the command execution
by the TARG. When the TARG asserts the BSY signal true in the SELECTION or
RESELECTION phase, the status change of SCSI bus is controlled by the TARG except for the
ATTENTION and RESET conditions.
The RESET condition can stop all bus phases and force the SCSI bus to switch to the BUS FREE
phase. Also, it can switch the bus from any phase to the BUS FREE phase.
Note:
The TARG can enter the BUS FREE phase in order to report an error condition. For details,
see Section 1.6.1.
Figure 1.43 shows the allowable bus phase sequence. Figure 1.44 provides an example of bus
phase sequence during single command execution.
Note:
Figure 1.43 shows the bus phase sequence applied to the system which uses the
ARBITRATION phase and the system which does not use the phase. Also, this Figure
compares the operations when the MESSAGE OUT phase is used and when it is not used.
The use of MESSAGE OUT phase is determined by the generation of ATTENTION condition
by the INIT. If the ATTENTION condition is not generated, the TARG assumes that the INIT
does not support any message other than the TASK COMPLETE and the TARG uses only the
TASK COMPLETE message in the subsequent command sequence.
36

Figure 1.42 RESET condition

C141-C015