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Memory Map
0x23FFFFFC
0x2200001C
7
6
7
6
4.2.1
Directly accessing an alias region
4.2.2
Directly accessing a bit-band region
4-6
0x23FFFFF8
0x23FFFFF4
0x22000018
0x22000014
5
4
3
2
1
0
7
6
5
0x200FFFFF
5
4
3
2
1
0
7
6
5
0x20000003
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
effect as writing
0xFF
Reading a word in the alias region returns either
that the targeted bit in the bit-band region is set. A value of
targeted bit is clear. Bits [31:1] are zero.
You can directly access the bit-band region with normal reads and writes, and writes to
that region.
Copyright © 2005-2008 ARM Limited. All rights reserved.
32MB alias region
0x23FFFFF0
0x23FFFFEC
0x22000010
0x2200000C
1MB SRAM bit-band region
4
3
2
1
0
7
6
5
0x200FFFFE
0x200FFFFD
4
3
2
1
0
7
6
5
0x20000002
0x20000001
. Writing
has the same effect as writing
0x00
Non-Confidential
0x23FFFFE8
0x23FFFFE4
0x22000008
0x22000004
4
3
2
1
0
7
6
5
4
0x200FFFFC
4
3
2
1
0
7
6
5
4
0x20000000
Figure 4-2 Bit-band mapping
0x01
0x0E
or
. A value of
0x01
0x00
indicates that the
0x00
0x23FFFFE0
0x22000000
3
2
1
0
3
2
1
0
has the same
.
indicates
0x01
ARM DDI 0337G
Unrestricted Access
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