Technical information

HGST Ultrastar C15K600 Hard Disk Drive Specification
215
18.21.5
Echo Buffer Descriptor (Mode 01011b)
In this mode, a maximum of four bytes of Read Buffer Descriptor information is returned. The drive returns the
descriptor information for the echo buffer. The Buffer Offset field is reserved in this mode and must be zero. The
drive transfers the lesser of the allocation length or four bytes of following Echo Buffer Descriptor.
Table 181 Echo Buffer Descriptor
Byte
Bit
7
6
5
4
3
2
1
0
0
Reserved = 0
EBOS=0
1
Reserved = 0
2
Reserved = 0
(MSB) Buffer Capacity
3
Buffer Capacity (LSB)
- EBOS (Echo Buffer Overwritten Supported) bit of zero indicates that the echo buffer is shared by all Initiators.
- Buffer Capacity field returns the size of the echo buffer in byte aligned to a 4-byte boundary.
18.21.6
Expander Communications and Echo Buffer (Mode 11010b)
Receipt of a READ BUFFER command with this mode (11010b) causes a communicative expander to enter the
expanded communication protocol mode. SCSI target devices that receive a READ BUFFER command with this
mode shall process it as if it were a READ BUFFER command with mode 01010b (see 17.17.4 Read Data from Echo
Buffer).
18.21.7
Error History (Mode 11100b)
The Buffer ID field specifies the action that the device server shall perform, and the parameter data, if any, that the
device server shall return.
Table 182 Error History Buffer ID Field
Code
Description
Buffer
Offset
Error History I_T
Nexus
Constrained
00h
Return error history directory
0000h
Yes
01h
Return error history directory and create new error history
snapshot
0000h Yes
02h
Return error history directory and establish new error history
I_T Nexus
0000h No
03h
Return error history directory, establish new error history I_T
Nexus, and create new error history snapshot
0000h No
04h to 0Fh
Reserved
Yes
10h to EFh Return error history
0000h to
FFFFh
Yes
F0h to FDh
Reserved
Yes
FEh
Clear error history I_T Nexus
Ignored
Yes