Bus Phases And Signal Sources - Fujitsu MAN3184 SERIES Specifications

(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
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.
Table 1.14

Bus phases and signal sources

I/O,
REQ,
BSY SEL
C/D,
MSG
N N N
A 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
C141-E123-01EN
ACK, DB15-8,
DB7-0
ATN DBP1
N N N
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
I A
T A
I A
T A
I A
T A
T A
T A
T A
I A
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