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T13/2132-D Revision 3
3.3.10 Byte, word, DWord, and QWord Relationships
Figure 2 illustrates the relationship between bytes, words, DWords, and QWords.
Byte
Word at offset n
DWord at word offset n
31 30 29 28 27 26 25 24
MSB
Byte 2n+3
QWord at word offset n
63
...
56 55
...
MSB
Byte 2n+7
Byte 2n+6
Word n+3
DWord n/2+1
Unless stated or defined otherwise, in a field containing a multi-byte value (e.g., a word, DWord, or QWord), the
byte containing the LSB is stored at the lowest offset and the byte containing the MSB is stored at the highest
offset.
3.3.11 ATA string convention
ATA strings are sequences of bytes containing ASCII graphic characters in the range of 20h-7Eh. ATA strings
shall not contain values in the range of 00h-1Fh or 7Fh-FFh.
10
23 22 21 20 19 18 17 16
Byte 2n+2
Word n+1
48
47
...
40 39
...
Byte 2n+5
Byte 2n+4
Word n+2
Figure 2 — Byte, word, DWord and QWord relationships
Working Draft Enhanced Disk Drive - 4 (EDD-4)
15 14 13 12 11 10 9 8
MSB
Byte 2n+1
DWord n/2
15 14 13 12 11 10 9 8
Byte 2n+1
QWord n/4
32
31
...
24 23
Byte 2n+3
Byte 2n+2
Word n+1
June 23, 2010
Byte
7 6 5 4 3 2 1 0
MSB
Word n
7 6 5 4 3 2 1 0
Byte 2n
7 6 5 4 3 2 1 0
Byte 2n
Word n
...
16
15
...
8 7
Byte 2n+1
Byte 2n
Word n
DWord n/2
LSB
LSB
LSB
...
0
LSB
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