Cortex-M3 Processor (Reference Material)
UG0331 User Guide Revision 15.0
29
3.5.2
Memory Model
This section describes the processor memory map, the behavior of memory accesses, and the
bit-banding features. The processor has a fixed memory map that provides up to 4GB of addressable
memory. The following illustration shows the processor memory map.
Figure 11 •
Processor Memory Map
The regions for SRAM and peripherals include bit-band regions. Bit-banding provides atomic operations
to bit data, see
The processor reserves regions of the Private peripheral bus (PPB) address range for core peripheral
registers, see
Cortex-M3 Processor Peripherals,
3.5.2.1
Memory Regions, Types and Attributes
The memory map and the programming of the MPU splits the memory map into regions. Each region has
a defined memory type, and some regions have additional memory attributes. The memory type and
attributes determine the behavior of accesses to the region.
The memory types are:
Normal:
The processor can re-order transactions for efficiency, or perform speculative reads.
Device:
The processor preserves transaction order relative to other transactions to Device or Strongly-
ordered memory.
Strongly-ordered:
The processor preserves transaction order relative to all other transactions Strongly-
Ordered or Device.
The different ordering requirements for Device and Strongly-ordered memory mean that the memory
system can buffer a write to Device memory, but must not buffer a write to Strongly-ordered memory.
Vendor-specific
memory
External device
External RAM
Peripheral
SRAM
Code
0xFFFFFFFF
Private peripheral
bus
0xE0100000
0xE00FFFFF
0x9FFFFFFF
0xA0000000
0x5FFFFFFF
0x60000000
0x3FFFFFFF
0x40000000
0x1FFFFFFF
0x20000000
0x00000000
0x40000000
Bit band region
Bit band alias
32MB
1MB
0x400FFFFF
0x42000000
0x43FFFFFF
Bit band region
Bit band alias
32MB
1MB
0x20000000
0x200FFFFF
0x22000000
0x23FFFFFF
1.0GB
1.0GB
0.5GB
0.5GB
0.5GB
0xDFFFFFFF
0xE0000000
1.0MB
511MB