Signal Sources; Table 3-3 Signal Source - Sun Microsystems storagetek sl500 Reference Manual

Signal Sources

TABLE 3-3

TABLE 3-3 Signal Source

Bus Phase
Bus Free
Arbitration
Selection
Reselection
Command
Data In
Data Out
Status
Message In
Message Out
Notes:
A The signal is driven by all SCSI devices arbitrating.
I If this signal is driven, it is driven only by the active initiator.
A unique data bit (the SCSI ID) is driven by each SCSI device that is arbitrating. The
ID
other 15 data bits are released (not driven) by this SCSI device.
The parity bit DB(P, P1) may be driven or undriven to the asserted state but will never
be driven to the negated state during this phase.
I&T The signal is driven by the initiator, target, or both, as specified in the Selection and
Reselection phases.
N The signal is released—that is, not driven—by any SCSI device.
The bias circuitry of the bus terminators pulls the signal to the negated state.
If the signal is driven, it is driven only by the active target.
T
The signal is driven by the device that wins during the arbitration phase.
W
96122 • Revision: F
indicates the source and phase of the SCSI bus signals.
BSY SEL
N
A
I & T
I & T
T
T
T
T
T
T
Bus Signals
C/D
I/O
MSG
REQ
N N
W N
I N
T T
N T
N T
N T
N T
N T
N T
Chapter 3 SCSI Bus Operations 19
Signal Sources
ACK
ATN DB
N N
N ID
I I
I I
I I
I T
I I
I T
I T
I I