Seagate Medalist 2160N (ST52160N), Руководство по эксплуатации продукта

Страница: 83 / 138

The offset boundary field returns the boundary alignment
within the selected buffer for subsequent WRITE BUFFER
and READ BUFFER commands. The value contained in the
offset boundary field shall be interpreted as a power of two.
Buffer Offset Boundary
Offset Boundary 20 Offset Boundary Buffer Offsets
5 2
5
= 32 32-byte boundaries
FF
H
Not Applicable
0 is the only
supported buffer
offset
The buffer capacity field returns the size of the selected
buffer in bytes.
All other settings for the mode bits are reserved.
Byte 2 The buffer ID is not supported and must always be zero.
Byte 3–5 The buffer offset is added to the starting address of the
buffer to determine the source of the first data byte. The
bytes that follow are read from sequential addresses. If the
sum of the buffer offset and the transfer length exceeds the
available length reported in the Read Buffer header (see
Section 3.6.9.1), the drive transfers all the data contained
in the buffer.
Bytes 6–8 The allocation length field specifies the maximum number
of bytes read by the initiator. If the 4-byte header is trans-
ferred, the transfer length includes the header. If the transfer
length is zero, no data is read;
this is not an error.
3.6.9.1 Read Buffer Header
The following table shows the structure of the 4-byte Read Buffer Header.
Bytes
Bits
7 6 5 4 3 2 1 0
0 0
1–3 Buffer capacity
Bytes 1–3 The buffer capacity field specifies the size of the drive
buffer. Byte 1 is MSB; byte 3 is LSB.
Medalist Pro 2160N/2160WC Product Manual, Rev. A 73