Fujitsu 600C manual Information Transfer phases, Information Transfer phase type Phase

4.3.4INFORMATION TRANSFER phases

Note:

The COMMAND, DATA, STATUS, and MESSAGE phases are all grouped together as the information transfer phases because they are a]l 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 4-6 INFORMATION TRANSFER phase type

Phase	C/D	I/O	MSG	DB7 to 9,P	Transfer
					direction
DATA OUT	0	0	0	Data	INIT ⇒TARG
DATAIN	0	1	0	Data	⇐
COMMAND	I	0	0	Command	⇒
STATUS	I	I	0	Status	⇐
*	0	0	1	⎯
*	0	1	I	⎯
MESSAGE OUT	1	0	1	Message	⇒
MESSAGEIN	1	1	1	Message	⇐

*: Reserved for future standardization

0:False

1:True

INIT: Initiator

TARG: Target

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