存储器大小端

内容简介 ：
Introduction
The term endianness refers to the way in which multiple elements of identical size are stored in memory. There are two conventions for storing bytes within multi-byte quantities, such as 32-bit words, in byte-addressed memory. In a little-endian architecture, the least significant byte of the quantity is stored at the lowest memory address in the range of addresses used to store the quantity. The reverse is true in a big-endian architecture, where the most significant byte is stored at the lowest address.
The ARM can be configured to be either little- or big-endian. This Application Note discusses the effect that choosing either little- or big-endian configuration has on byte and halfword addressing.
For more information on endianness, please see:

• Computer Architecture - A Quantitive Approach, Henessey & Patterson, page 73, 2nd Ed, Publisher: Morgan Kaufman, ISBN: 1-55860-32908.
• ARM System Architecture, Steve Furber, page 110, 1st Ed, Publisher:
  Addison-Wesley, ISBN 0-201-40352-8.

Note The basic endian configuration principles described in this application note are applicable to all ARM cores and AMBA-based systems. However, the signal names used are specific to ARM7TDMI. For equivalent signal names for other ARM cores, or AMBA-based systems, please refer to the appropriate datasheet.

Table of Contents

1. Introduction
2. Configuring the Endianness of the ARM
3. Effect of Endian Configuration on the System
   3.1 Connection to memory
   3.2 Word accesses to memory
   3.3 Byte and halfword accesses to memory
4. Little-Endian Operation
   4.1 Connection to memory
   4.2 Word accesses to memory
   4.3 Byte and halfword accesses to memory
5. Big-Endian Operation
   5.1 Connection to memory
   5.2 Word accesses to memory
   5.3 Byte and halfword accesses to memory.