Technical information

HGST Ultrastar C15K600 Hard Disk Drive Specification
213
18.21.1
Combined Header And Data (Mode 00000b)
In this mode a 4-byte header followed by data bytes is returned to the Initiator during the DATA IN phase. The Buffer
ID and the buffer offset field are reserved.
The drive terminates the DATA IN phase when allocation length bytes of header plus data have been transferred or
when the header and all available data have been transferred to the Initiator, whichever is less.
The 4-byte READ BUFFER header (see figure below) is followed by data bytes from the data buffer of the drive.
Table 179 Read Buffer Header
Byte
Bit
7
6
5
4
3
2
1
0
RSVD = 0
1-3
(MSB)
Buffer Capacity
(LSB)
The buffer capacity specifies the total number of data bytes that are available in the data buffer of the drive. This
number is not reduced to reflect the allocation length nor is it reduced to reflect the actual number of bytes written
using the WRITE BUFFER command.
Following the READ BUFFER header the drive will transfer data from its data buffer.
18.21.2
Read Data (Mode 00010b)
In this mode, the DATA IN phase contains buffer data.
- Buffer ID field must be set to zero, indicating the data transfer buffer. If another value is specified, the results
may be unpredictable.
- Buffer Offset specifies the offset of the memory space specified by the Buffer ID. The Initiator should conform
to the offset boundary requirements returned in the READ BUFFER descriptor. If the value exceeds the buffer
specified, the command is terminated with Check Condition status. The drive shall set sense key to Illegal
Request and additional sense code to Illegal Field in CDB.
- Allocation Length The drive terminates the DATA IN phase when allocation length bytes of data have been
transferred or when the header and all available data have been transferred to the Initiator, whichever is less.