ARM Cortex-M3 User Manual

Memory Map
4-6 Copyright © 2005-2008 ARM Limited. All rights reserved. ARM DDI 0337G
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Figure 4-2 Bit-band mapping
4.2.1 Directly accessing an alias region
Writing to a word in the alias region has the same effect as a read-modify-write
operation on the targeted bit in the bit-band region.
Bit [0] of the value written to a word in the alias region determines the value written to
the targeted bit in the bit-band region. Writing a value with bit [0] set writes a 1 to the
bit-band bit, and writing a value with bit [0] cleared writes a 0 to the bit-band bit.
Bits [31:1] of the alias word have no effect on the bit-band bit. Writing
0x01 has the same
effect as writing
0xFF . Writing 0x00 has the same effect as writing 0x0E .
Reading a word in the alias region returns either
0x01 or 0x00 . A value of 0x01 indicates
that the targeted bit in the bit-band region is set. A value of
0x00 indicates that the
targeted bit is clear. Bits [31:1] are zero.
4.2.2 Directly accessing a bit-band region
You can directly access the bit-band region with normal reads and writes, and writes to
that region.
0x23FFFFE4
0x22000004
0x23FFFFE00x23FFFFE80x23FFFFEC0x23FFFFF00x23FFFFF40x23FFFFF80x23FFFFFC
0x220000000x220000140x220000180x2200001C 0x220000080x22000010 0x2200000C
32MB alias region
0
7 0
07
0x200000000x200000010x200000020x20000003
6 5 4 3 2 1 07 6 5 4 3 2 1 7 6 5 4 3 2 1 07 6 5 4 3 2 1
07 6 5 4 3 2 1 6 5 4 3 2 107 6 5 4 3 2 1 07 6 5 4 3 2 1
0x200FFFFC0x200FFFFD0x200FFFFE0x200FFFFF
1MB SRAM bit-band region

ARM Cortex-M3 Specifications

General

Architecture	ARMv7-M
Instruction Set	Thumb-2
Pipeline Stages	3-stage
Interrupts	Nested Vectored Interrupt Controller (NVIC)
Interrupt Controller	Nested Vectored Interrupt Controller (NVIC)
Memory Protection Unit	Optional
Power Consumption	Varies by implementation
Max Clock Speed	Up to 100 MHz
Debugging	JTAG and Serial Wire Debug (SWD)
Operating Voltage	1.8V to 3.6V
Manufacturing Process	Varies by implementation
Core Type	32-bit