Table of Contents
Advertisement
SCSI BUS
(3) Signal sources
Table 7.6 lists signal sources for each interface phase.
Signal
BSY
Bus phase
BUS FREE
ARBIRATION
SELECTION
I&T
RESELECTION
I&T
COMMAND
DATA IN
DATA OUT
STATUS
MESSAGE IN
MESSAGE OUT
A:
I:
I&T: INIT, TARG, or both can drive this signal according to the interface
ID:
N:
T:
W:
7-14
Table 7.6 Bus phases and signal sources
SEL
I/O
N
N
N
A
W
N
I
N
T
T
T
N
T
T
N
T
T
N
T
T
N
T
T
N
T
T
N
T
Any SCSI device can drive the signal. Two or more SCSI devices may
drive the signal at the same time.
Only the SCSI device which operates as an INIT can drive the signal.
sequence.
In the RESELECTION phase, there is a sequence to be driven
simultaneously by both.
Each SCSI device which is actively arbitrating the bus drives a unique data
bit (SCSI ID). The parity bit may be undriven or driven to the true state, but
must never be driven to the false state.
Not to be driven by any SCSI device. The terminator pulls the signal to the
false state.
Only the SCSI device which operates as an TARG can drive the signal.
Only one SCSI device which wins ARBITRATION can drive the signal.
C/D
REQ
ACK
MSG
N
N
N
N
N
N
N
N
N
N
N
N
T
T
I
T
T
I
T
T
I
T
T
I
T
T
I
T
T
I
DB7-0,
ATN
TRS
P
N
N
A
ID
N
A
I
I
A
T
I
A
I
I
A
T
I
A
I
I
A
T
I
A
T
I
A
I
I
A
C156-E228-02EN
Hide quick links:
Advertisement
Table of Contents
