CHAPTER 1 INTRODUCTION
User’s Manual U14272EJ3V0UM
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The CPU core uses the following byte boundaries for halfword, word, and doubleword accesses:
•
Halfword:
An even byte boundary (0, 2, 4...)
•
Word:
A byte boundary divisible by four (0, 4, 8...)
•
Doubleword:
A byte boundary divisible by eight (0, 8, 16...)
The following special instructions are used to load and store data that are not aligned on 4-byte (word) or 8-byte
(doubleword) boundaries:
•
Word access:
LWL, LWR, SWL, SWR
•
Doubleword access: LDL, LDR, SDL, SDR
These instructions are used in pairs of L and R.
Accessing unaligned data requires one additional instruction cycle (1 PCycle) over that required for accessing
aligned data.
Figure 1-7 shows the access of an unaligned word that has byte address 3.
Figure 1-7. Unaligned Word Accessing (Little Endian)
31
24 23
16 15
8 7
0
6
5
4
3
High-order address
Low-order address
