Spinpoint M8U-Internal Product Manual REV 3.4
92
INSTALLATION
6.4.4.2 Valid and Meaningful CBW
The host communicates its intent to the device through the CBW. The device performs two verifications on
every CBW received. First, the device verifies that what was received is a valid CBW. Next, the device
determines if the data within the CBW is meaningful.
The device shall not use the contents of the
dCBWTag
in any way other than to copy its value to the
dCSWTag
of the corresponding CSW.
■
Valid CBW
The device shall consider the CBW valid when:
•
The CBW was received after the device had sent a CSW or after a reset,
•
the CBW is 31 (1Fh) bytes in length,
•
and the
dCBWSignature
is equal to 43425355h.
■
Meaningful CBW
The device shall consider the contents of a valid CBW meaningful when:
•
no reserved bits are set,
•
the
bCBWLUN
contains a valid LUN supported by the device,
•
and both
bCBWCBLength
and the content of the
CBWCB
are in accordance with
bInterfaceSubClass
.
6.4.4.3 Valid and Meaningful CSW
The device generally communicates the results of its attempt to satisfy the host’s request through the CSW.
The host performs two verifications on every CSW received. First, the host verifies that what was received is
a valid CSW Next, the host determines if the data within the CSW is meaningful.
■
Valid CSW
The host shall consider the CSW valid when:
•
the CSW is 13 (Dh) bytes in length,
•
and the
dCSWSignature
is equal to 53425355h,
•
the
dCSWTag
matches the
dCBWTag
from the corresponding CBW.
■
Meaningful CSW
The host shall consider the contents of the CSW meaningful when:
either the
bCSWStatus
value is 00h or 01h and the
dCSWDataResidue
is less than or equal to
dCBWDataTransferLength
..
or the
bCSWStatus
value is 02h.
