Nec Network Controller uPD98502 Uživatelský manuál Strana 228

  • Stažení
  • Přidat do mých příruček
  • Tisk
  • Strana
    / 595
  • Tabulka s obsahem
  • KNIHY
  • Hodnocené. / 5. Na základě hodnocení zákazníků
Zobrazit stránku 227
CHAPTER 3 SYSTEM CONTROLLER
228
Preliminary User’s Manual S15543EJ1V0UM
However, when making half-word accesses into a data array consisting of word data, access to the more-
significant half word requires the address corresponding to the less significant half word (and vice versa). Such code
is not endian-independent. A super-group access (for example, accessing two half words simultaneously as a word
from a half-word data array) causes the same problem. Such problems also arise when a half-word access is made
into a 32-bit register, whereas a word access into a 32-bit register creates no problem.
Figure 3-3. Word Data Array Example
Word
Data Array
Big-Endian
Data extraction using sequential halfword access
W1
W0
LSHWMSHW
Little-Endian
MSHW LSHW
A B C D
E F G H
I J K L
M N O P
A B C D
E F G H
I J K L
M N O P
Order Retained
Data extraction using sequential halfword access
A B C D E F G H
I J K L M N O P
Order Lost
A B C D E F G H
I J K L M N O P W1
W0 A B C D E F G H
I J K L M N O P
A B C D E F G H
I J K L M N O P
Zobrazit stránku 227
1 2 ... 223 224 225 226 227 228 229 230 231 232 233 ... 594 595

Komentáře k této Příručce

Žádné komentáře