Western Digital T13/2132-D - Manual (Page 22)

T13/2132-D Revision 3 June 23, 2010
10 Working Draft Enhanced Disk Drive - 4 (EDD-4)
3.3.10 Byte, word, DWord, and QWord Relationships
Figure 2 illustrates the relationship between bytes, words, DWords, and QWords.
Figure 2 — Byte, word, DWord and QWord relationships
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.
QWord n/4
DWord n/2
Word n
Byte
7 6 5 4 3 2 1 0
Byte
7 6 5 4 3 2 1 0
Word at offset n
15 14 13 12 11 10 9 8
7 6 5 4 3 2 1 0
DWord at word offset n
15 14 13 12 11 10 9 8 23 22 21 20 19 18 17 16 31 30 29 28 27 26 25 24
Byte 2n Byte 2n+1
MSB LSB
Byte 2n Byte 2n+1 Byte 2n+2 Byte 2n+3
15 8 7 0
QWord at word offset n
31 24 23 16 47 40 39 32 63 56 55 48
Byte 2n
Word n Word n+1
... ... ... ... ... ... ... ...
MSB
MSB
LSB
LSB
DWord n/2 DWord n/2+1
Word n Word n+1 Word n+2 Word n+3
MSB LSB
Byte 2n+1 Byte 2n+2 Byte 2n+3 Byte 2n+4 Byte 2n+5 Byte 2n+6 Byte 2n+7