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SAM4CP [DATASHEET]
43051E–ATPL–08/14
12.4.2.3 Behavior of Memory Accesses
The following table describes the behavior of accesses to each region in the memory map.
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 constraints, and some regions
are subdivided, as
Table 12-5
shows:
Notes: 1.
See
“Memory Regions, Types and Attributes”
for more information.
Table 12-4.
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 12-6
.
0x40000000 - 0x5FFFFFFF
Peripheral
Device
(1)
XN
This region includes bit band and bit band
alias areas, see
Table 12-6
.
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 12-5.
Memory Region Shareability Policies
Address Range
Memory Region
Memory Type
Shareability
0x00000000 - 0x1FFFFFFF
Code
Normal
(1)
-
0x20000000 - 0x3FFFFFFF
SRAM
Normal
(1)
-
0x40000000 - 0x5FFFFFFF
Peripheral
Device
(1)
-
0x60000000 - 0x7FFFFFFF
External RAM
Normal
(1)
-
0x80000000 - 0x9FFFFFFF
0xA0000000 - 0xBFFFFFFF
External device
Device
(1)
Shareable
(1)
0xC0000000 - 0xDFFFFFFF
Non-shareable
(1)
0xE0000000 - 0xE00FFFFF
Private Peripheral Bus
Strongly- ordered
(1)
Shareable
(1)
0xE0100000 - 0xFFFFFFFF
Vendor-specific device
Device
(1)
-