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3-20 M3099GX/GH OEM Manual
Table 3.6 Information Transfer Phases
Comment
Data
Phase
Message
Phase
Phase Name
DATA OUT
DATA IN
COMMAND
STATUS
*
*
MESSAGE OUT
MESSAGE IN
Direction of Transfer
Initiator to target
Initiator from target
Initiator to target
Initiator from target
Initiator to target
Initiator to target
Signal
MSG
0
0
0
0
1
1
1
1
C/D
0
0
1
1
0
0
1
1
I/O
0
1
0
1
0
1
0
1
Key: 0 = False, 1 = True, * = Reserved for future standardization
Asynchronous Information Transfer
The target shall control the direction of information transfer by
means of the I/O signal. When the I/O signal is true, information
shall be transferred from the target to the initiator. When the I/O
signal is false, information shall be transferred from the initiator to
the target. If the I/O signal is true (transfer to the initiator), the
target shall first drive the DB(7-0,P) signals to their desired values,
delay at least one deskew delay plus a cable skew delay, then assert
the REQ signal. The DB(7-0,P) signals shall remain valid until the
ACK signal is true at the target. The initiator shall read the DB(7-
0,P) signals after the REQ signal is true, then indicate its acceptance
of the data by asserting the ACK signal. When the ACK signal
becomes true at the target, the target may change or release the
DB(7-0,P) signals and shall negate the REQ signal. After the REQ
signal is false the initiator shall then negate the ACK signal. After the
ACK signal is false the target may continue the transfer by dividing
the DB(7-0,P) signals and asserting the REQ signal, as described
above.
#03.pm5 98.2.22, 1:31 PM20