Seagate ST3285N, Product Manual

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Byte 3–5 The
buffer offset is added to the starting address of the
buffer to determine the destination of the first data byte. The
bytes that follow are placed in sequential addresses. If the
sum of the buffer offset and the transfer length exceeds the
buffer size reported by the Read Buffer command (see
Section 3.5.9), the drive generates a check condition status
and the initiator does not transfer any data.
Bytes 6–8 The parameter list length field specifies the maximum num-
ber of bytes the initiator transfers. If it transfers the 4-byte
header, the transfer length includes the header. If the
transfer length is zero, no data is transferred to the drive
buffer. This is not considered an error.
3.5.9 Read Buffer command (3C
H
)
In conjunction with the Write Buffer command, the Read Buffer command
can be used in the following ways:
•
To diagnose problems in the drive’s data buffer.
•
To test the integrity of the SCSI bus.
Note. This command treats the buffer as a single segment, regardless
of the number of segments specified in Mode Page 08
H
. (Mode
Page 08
H
is described in Section C.5.)
Bit
Byte
7 6 5 4 3 2 1 0
0 0 0 1 1 1 1 0 0
1 LUN 0 0 Mode
2 Buffer ID (00
H
)
3–5 Buffer offset
6–8 Allocation length
9 0 0 0 0 0 0 Flag Link
Byte 1 If the
mode bits contain 000, the initiator reads data from
the drive buffer. The data is preceded by a 4-byte header.
This mode is called
read combined header and data.
If the mode bits contain 010, the initiator reads data from
the drive buffer without a header. This mode is called read
data.
All other settings for the mode bits are reserved.
Byte 2 The buffer ID is not supported and must always be zero.
ST3655 Family SCSI Drives Product Manual, Rev. A 71