Table 1.14 Bus Phases And Signal Sources - Fujitsu MBA3073 SERIES Technical Manual

(3) Signal sources
Table 1.14 lists SCSI device types (or signal sources) which can drive signals in each interface
operating phase.
BUS FREE
ARBITRATION
QAS ARBITRATION
SELECTION
RESELECTION
COMMAND
ST DATA IN
ST DATA OUT
DT DATA IN
DT DATA OUT
STATUS
MESSAGE IN
MESSAGE OUT
A: Any SCSI device can drive the signal. Also, two or more SCSI devices may drive the signal
simultaneously.
I: Only the INIT SCSI device drives the signal.
I&T: The INIT and TARG SCSI devices drive the signal in the interface operating sequence.
INIT, TARG or both can drive this signal according to the interface sequence.
I or T: The INIT or TARG SCSI device (or both devices) may drive the signal depending on the
I/O signal status and bus width.
ID: 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.
N: Not be driven by any SCSI device.
T: Only the TARG SCSI device drives the signal.
W: Only a single SCSI device selected through arbitration drives the signal.
C141-C015
Table 1.14 Bus phases and signal sources
I/O,
REQ,
BSY SEL
C/D,
MSG
N N N
A W N
PT W N
I&T I N
I&T T T
T N T
T N T
T N T
T N T
T N T
T N T
T N T
T N T
ACK
DB15-8,
, DB7-0
DBP1
ATN
N N N
N ID ID
N ID ID
I I I
I T T
I I N
I T T
I I I
I T T
I I I
I T N
I T N
I I N
P_CRCA RST
N A
ID A
ID ID
I A
T A
I A
T A
I A
T A
T A
T A
T A
I A
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