272
Western Digital Hard Disk Drive OEM Specification
11.51.3
Device Attribute Thresholds Data Structure
The following defines the 512 bytes that make up the Attribute Threshold information. This data structure is
accessed by the host in its entirety using the SMART Read Attribute Thresholds. All multi -byte fields shown in these
data structures follow the ATA/ATAPI-7 specification for byte ordering, namely that the least significant byte occupies
the lowest numbered byte address location in the field.
The sequence of active Attribute Thresholds will appear in the same order as their corresponding Attribute Values.
Description
Bytes
Offset
Value
Data Structure Revision Number
2
00h
0010h
1
st
Attribute Threshold
12
02h
…
..
…
..
30
th
Attribute Threshold
12
15Eh
Reserved
18
16Ah
00h
Vendor specific
131
17Ch
00h
Data structure checksum
1
1FFh
512
Table 232 Device Attribute Thresholds Data Structure
11.51.3.1
Data Structure Revision Number
This value is the same as the value used in the Device Attributes Values Data Structure.
11.51.3.2
Individual Thresholds Data Structure
The following defines the 12 bytes that make up the information for each Threshold entry in the Device Attribute
Thresholds Data Structure. Attribute entries in the Individual Threshold Data Structure are in the same order and
correspond to the entries in the Individual Attribute Data Structure.
Description
Bytes
Offset
Attribute ID Number (01h to FFh)
1
00h
Attribute Threshold
1
01h
Reserved (00h)
10
02h
Total Bytes
12
Table 233 Individual Threshold Data Structure
11.51.3.3
Attribute ID Numbers
Attribute ID Numbers supported by the device are the same as Attribute Values Data Structures.
11.51.3.4
Attribute Threshold
These values are preset at the factory and are not meant to be changeable.
11.51.3.5
Data Structure Checksum
The Data Structure Checksum is the 2’s compliment of the result of a simple 8-bit addition of the first 511 bytes in the
data structure.
