Wide Mode Transfer (16-Bit Scsi); Command Phase; Data Phase; Data Sequence At Data Transfer - Fujitsu MAN3184 SERIES Specifications

1.6.5.3 Wide mode transfer (16-bit SCSI)

The wide mode transfer enables information transfer using a multiple-byte-wide data bus. It is
used only in DATA phases.
In wide mode transfer, the WIDE DATA TRANSFER REQUEST or PARALLEL PROTOCOL
REQUEST message should first be exchanged by the INIT and the TARG to define the data
transfer mode between SCSI devices.
PARALLEL PROTOCOL REQUEST message is exchanged, a data bus width is determined.
Figure 1.29 shows the data sequence at data transfer. When a wide data transfer agreement is
negotiated in PARALLEL PROTOCOL REQUEST data bus width is determined 16 bit mode
automatically.
Note:
The IDD supports 8-bit and 16-bit transfer modes. The initial value of the data bus width is
"8-bit mode". After power is turned on, a RESET condition occurs, or a TARGET RESET
message is received, data is transferred using 8-bit mode until the mode is switched to "16-bit
mode" by exchanging the WIDE DATA TRANSFER REQUEST message.
Number of information
items transferred
1.6.6

COMMAND phase

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.
1.6.7

DATA 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) DT DATA IN phase
The DT DATA IN phase allows the target to request that data be sent to the initiator from the
target using DT data transfers. The target shall assert the I/O and MSG signals and negate the C/D
signal during the REQ/ACK handshake(s) of this phase.
1 Unused
2 Unused
DB15.................DB8 DB7..................DB0
1
Figure 1.29 Data sequence at data transfer
C141-E123-01EN
When the WIDE DATA TRANSFER REQUEST or
P cable
B
A "8-bit mode"
B
A "16-bit mode"
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