Information Transfer Phases; Information Transfer Phase Type - Fujitsu M3097G Oem Manual

4.3.5

INFORMATION TRANSFER phases

Note:
The COMMAND, DATA, STATUS, and MESSAGE phases are all grouped
together as the information transfer phases because they are all used to transfer
data or control information via the DATA BUS. The actual content of the
information is beyond the scope of this section.
The C/D, I/O, and MSG signals are used to distinguish between the different
information transfer phases (see Table 4.5). The target drives these three signals
and therefore controls all changes from one phase to another. The initiator can
request a MESSAGE OUT phase by asserting the ATN signal, while the target can
cause the BUS FREE phase by releasing the MSG, C/D, I/O, and BSY signals.
Table 4.5 INFORMATION TRANSFER phase type
Phase
DATA OUT
DATA IN
COMMAND
STATUS
*
*
MESSAGE OUT
MESSAGE IN
0: False
1 True
INIT: Initiator
TARG: Target
C/D I/O MSG
0 0 0
0 1 0
1 0 0
1 1 0
0 0 1
0 1 1
1 0 1
1 1 1
DB7 to 0, P Transfer direction
Data INIT
Data INIT
Command INIT
Status INIT
Message INIT
Message INIT
* : Reserved for future standardization
TARG
TARG
TARG
TARG
TARG
TARG
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