Seagate Medalist 2160N (ST52160N), Product Manual

Page: 99 / 138

A.2.1 Wide Data Transfer Request Message
Bytes
Bits
7 6 5 4 3 2 1 0
0 Extended message (01
H
)
1 Extended message length (02
H
)
2 Wide Data Transfer Request code (03
H
)
3 Transfer Width Exponent
The originating SCSI device (the SCSI device that sends the first pair of
WDTR messages) sets its transfer value to the maximum data path it
chooses to accommodate.
If the responding SCSI device can also accommodate this transfer width,
it returns the same value in its WDTR message. If it requires a smaller
transfer width, it substitutes a smaller value in its WDTR message. The
successful completion of an exchange of WDTR messages implies an
agreement as follows:
Responding Device
WDTR Response
Implied Agreement
Nonzero transfer width
Each device transmits and
receives data with a transfer
width equal to the
responding SCSI devices’
transfer width
Transfer width equal to zero 8-bit data transfer
MESSAGE REJECT message
8-bit data transfer
Medalist Pro 2160N/2160WC Product Manual, Rev. A 89