Atmel SAM4S Series, Preliminary Data Sheet

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11100B–ATARM–31-Jul-12
SAM4S Series [Preliminary]
Where:
- Means that the memory system does not guarantee the ordering of the accesses.
< Means that accesses are observed in program order, that is, A1 is always observed
before A2.
11.4.2.3 Behavior of Memory Accesses
The behavior of accesses to each region in the memory map is:
Note: 1. See “Memory Regions, Types and Attributes” for more information.
The Code, SRAM, and external RAM regions can hold programs. However, ARM recommends
that programs always use the Code region. This is because the processor has separate buses
that enable instruction fetches and data accesses to occur simultaneously.
The MPU can override the default memory access behavior described in this section. For more
information, see
“Memory Protection Unit (MPU)” .
Additional Memory Access Constraints For Shared Memory
When a system includes shared memory, some memory regions have additional access con-
straints, and some regions are subdivided, as
Table 11-5 shows:
Table 11-4. Memory Access Behavior
Address Range Memory Region
Memory
Type
XN Description
0x00000000 - 0x1FFFFFFF Code Normal
(1)
-
Executable region for program code. Data can also be
put here.
0x20000000 - 0x3FFFFFFF SRAM Normal
(1)
-
Executable region for data. Code can also be put here.
This region includes bit band and bit band alias areas,
see
Table 11-6 .
0x40000000 - 0x5FFFFFFF Peripheral Device
(1)
XN
This region includes bit band and bit band alias areas,
see
Table 11-6 .
0x60000000 - 0x9FFFFFFF External RAM Normal
(1)
- Executable region for data.
0xA0000000 - 0xDFFFFFFF External device Device
(1)
XN External Device memory
0xE0000000 - 0xE00FFFFF Private Peripheral Bus
Strongly-
ordered
(1)
XN
This region includes the NVIC, System timer, and
system control block.
0xE0100000 - 0xFFFFFFFF Reserved Device
(1)
XN Reserved
Table 11-5. Memory Region Shareability Policies
Address Range Memory Region Memory Type Shareability
0x00000000-
0x1FFFFFFF
Code Normal
(1)
-
(2)
0x20000000-
0x3FFFFFFF
SRAM Normal
(1)
-
(2)
0x40000000-
0x5FFFFFFF
Peripheral Device
(1)
-