Справочник Пользователя для Samsung S3C2440A
PROGRAMMER'S MODEL
S3C2440A RISC MICROPROCESSOR
2-2
BIG-ENDIAN FORMAT
In Big-Endian format, the most significant byte of a word is stored at the lowest numbered byte and the least
significant byte at the highest numbered byte. Byte 0 of the memory system is therefore connected to data lines 31
through 24.
significant byte at the highest numbered byte. Byte 0 of the memory system is therefore connected to data lines 31
through 24.
31
8
4
0
23
9
5
1
10
6
2
11
7
3
8
7
0
4
0
8
Higher Address
Lower Address
Word Address
Most significant byte is at lowest address.
Word is addressed by byte address of most significant byte.
Word is addressed by byte address of most significant byte.
24
15
16
Figure 2-1. Big-Endian Addresses of Bytes within Words
LITTLE-ENDIAN FORMAT
In Little-Endian format, the lowest numbered byte in a word is considered the word's least significant byte, and the
highest numbered byte the most significant. Byte 0 of the memory system is therefore connected to data lines 7
through 0.
highest numbered byte the most significant. Byte 0 of the memory system is therefore connected to data lines 7
through 0.
31
23
8
7
0
4
0
8
Higher Address
Lower Address
Word Address
Least significant byte is at lowest address.
Word is addressed by byte address of least significant byte.
Word is addressed by byte address of least significant byte.
24
15
16
8
4
0
9
5
1
10
6
2
11
7
3
Figure 2-2. Little-Endian Addresses of Bytes within Words
INSTRUCTION LENGTH
Instructions are either 32 bits long (in ARM state) or 16 bits long (in THUMB state).
Data Types
ARM920T supports byte (8-bit), halfword (16-bit) and word (32-bit) data types. Words must be aligned to four-byte
boundaries and half words to two-byte boundaries.
boundaries and half words to two-byte boundaries.