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Memory formats

The processor views memory as a linear collection of bytes numbered in ascending order from zero. For example, bytes 0-3 in memory hold the first stored word, and bytes 4-7 hold the second stored word.

The processor can treat words in memory as either:

    * Byte-invariant big-endian format

    *Little-endian format.

Additionally, the processor supports mixed-endian and unaligned data accesses. See Chapter 4 Unaligned Data and Mixed-endian Data Support for details.

Note

Instructions are always treated as little-endian.

Byte-invariant big-endian format

In byte-invariant big-endian format, the processor stores the most significant byte of a word at the lowest-numbered byte, and the least significant byte at the highest-numbered byte. Therefore, byte 0 of the memory system connects to data.

Little Endian Format

In little-endian format, the lowest-numbered byte in a word is the least significant byte of the word and the highest-numbered byte is the most significant. Therefore, byte 0 of the memory system connects to data lines.