Fujitsu MCE3064SS User Manual

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C156-E097-01EN

The COMMAND phase is a bus phase in which the TARG requests the INIT to transfer
command information (CDB) to the TARG.  The TARG keeps the C/D signal true and the I/O
and MSG signals false during REQ/ACK handshaking in this phase.

The DATA phase is divided into DATA IN and DATA OUT phases according to the direction of
data transfer.  In a DATA phase, synchronous data transfer can be performed.

(1)

DATA IN phase

In a DATA IN phase, the TARG requests to transfer data from the TARG to the INIT.  The
TARG keeps the I/O signal true and the C/D and MSG signals false during REQ/ACK
handshaking in this phase.

(2)

DATA OUT phase

In a DATA OUT phase, the TARG requests to transfer data from the INIT to the TARG. The
TARG keeps the C/D, I/O, and MSG signals false during REQ/ACK handshaking in this phase.

(3)

Data transfer rate in asynchronous mode

Figure 7.13 shows the REQ/ACK handshake timing that the ODD observes in a DATA phase
where asynchronous transfer is used.  The data transfer rate on the SCSI bus depends on sum of
the ACK response time in the INIT and the signal delay time of the interface cable (T1 and T2 in
Figure 7.13).