AVR32AP datasheet(48/181 Pages) ATMEL

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32001A–AVR32–06/06

AVR32

Virtual memory

The AVR32 architecture uses virtual memory in order to support operating systems and large

memory spaces efficiently. Virtual memory simplifies execution of multiple processes and allows

allocation of privileges to different sections of the memory space.

The AVR32 architecture specifies a 32-bit virtual memory space. This virtual space can be

mapped to a 32-bit physical space. How this memory space is used and mapped is defined by

bus controllers and memory controllers on the outside of AVR32 AP.

4.1

Memory map

The memory map has six different segments, named P0 through P4, and U0. The P-segments

are accessible in the privileged modes, while the U-segment is accessible in the unprivileged

mode.

The virtual memory map is specified below.

Figure 4-1.

The AVR32 virtual memory space

Both the P1 and P2 segments are default segment translated to the physical address range

0x00000000 to 0x1FFFFFFF. The mapping between virtual addresses and physical addresses

is therefore implemented by clearing of MSBs in the virtual address. The difference between P1

and P2 is that P1 is cached, while P2 is uncached. Because P1 and P2 are segment translated

and not page translated, code for initialization of MMUs and exception vectors are located in

these segments. P1, being cacheable, offers higher performance than P2.

The P3 space is also by default segment translated to the physical address range 0x00000000

to 0x1FFFFFFF. By enabling and setting up the MMU, the P3 space becomes page translated.

Page translation will override segment translation.

The P4 space is intended for memory mapping special system resources like peripheral mod-

ules. This segment is non-cacheable, non-translated.

2GB translated space

Cacheable

512MB system space,

non-cacheable

512MB translated space,

cacheable

512MB non-translated

space, non-cacheable

512MB non-translated

space, cacheable

Unaccessible space

Access error

2GB translated space

Cacheable

0x00000000

0x80000000

0xA0000000

0xC0000000

0xE0000000

0xFFFFFFFF

Privileged Modes

Unprivileged Mode

0x00000000

0x80000000

0xFFFFFFFF

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