SAM3X8C Atmel Corporation, SAM3X8C Datasheet - Page 73

• Manufacturer Part Number: SAM3X8C
• Manufacturer: Atmel Corporation

11.5.5.1
11.5.5.2
11.5.6
11057A–ATARM–17-Feb-12
11057A–ATARM–17-Feb-12
Memory endianness
Directly accessing an alias region
Directly accessing a bit-band region
Figure 11-2. Bit-band mapping
Writing to a word in the alias region updates a single 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 tar-
geted bit in the bit-band region. Writing a value with bit[0] set to 1 writes a 1 to the bit-band bit,
and writing a value with bit[0] set to 0 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:
“Behavior of memory accesses” on page 69
word accesses to the bit-band regions.
The processor views memory as a linear collection of bytes numbered in ascending order from
zero. For example, bytes 0-3 hold the first stored word, and bytes 4-7 hold the second stored
word. or
• 0x00000000 indicates that the targeted bit in the bit-band region is set to zero
• 0x00000001 indicates that the targeted bit in the bit-band region is set to 1
7
7
0x23FFFFFC
0x2200001C
6
6
“Little-endian format”
5
5
0x200FFFFF
0x20000003
4
4
3
3
0x23FFFFF8
0x22000018
2
2
1
1
0
0
7
7
0x23FFFFF4
0x22000014
6
6
describes how words of data are stored in memory.
5
5
0x200FFFFE
0x20000002
4
4
1MB SRAM bit-band region
3
3
0x23FFFFF0
0x22000010
32MB alias region
2
2
1
1
0
0
describes the behavior of direct byte, halfword, or
7
7
0x23FFFFEC
0x2200000C
6
6
5
5
0x200FFFFD
0x20000001
4
4
3
3
0x23FFFFE8
0x22000008
2
2
1
1
0
0
7
7
0x23FFFFE4
0x22000004
6
6
5
5
0x200FFFFC
0x20000000
4
4
SAM3X/A
SAM3X/A
3
3
0x23FFFFE0
0x22000000
2
2
1
1
0
0
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