SAM3N0C Atmel Corporation, SAM3N0C Datasheet - Page 60

• Manufacturer Part Number: SAM3N0C
• Manufacturer: Atmel Corporation

10.5.5.1
60
SAM3N
Directly accessing an alias region
where:
Figure 10-2
the SRAM bit-band region:
Figure 10-2. 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.
• Bit_word_offset is the position of the target bit in the bit-band memory region.
• Bit_word_addr is the address of the word in the alias memory region that maps to the
• Bit_band_base is the starting address of the alias region.
• Byte_offset is the number of the byte in the bit-band region that contains the targeted bit.
• Bit_number is the bit position, 0-7, of the targeted bit.
• The alias word at 0x23FFFFE0 maps to bit[0] of the bit-band byte at 0x200FFFFF: 0x23FFFFE0 =
• The alias word at 0x23FFFFFC maps to bit[7] of the bit-band byte at 0x200FFFFF: 0x23FFFFFC =
• The alias word at 0x22000000 maps to bit[0] of the bit-band byte at 0x20000000: 0x22000000 =
• The alias word at 0x2200001C maps to bit[7] of the bit-band byte at 0x20000000: 0x2200001C =
targeted bit.
0x22000000 + (0xFFFFF*32) + (0*4).
0x22000000 + (0xFFFFF*32) + (7*4).
0x22000000 + (0*32) + (0 *4).
0x22000000+ (0*32) + (7*4).
bit_word_addr = bit_band_base + bit_word_offset
7
7
0x23FFFFFC
0x2200001C
6
6
5
5
0x200FFFFF
0x20000003
shows examples of bit-band mapping between the SRAM bit-band alias region and
4
4
3
3
0x23FFFFF8
0x22000018
2
2
1
1
0
0
7
7
0x23FFFFF4
0x22000014
6
6
5
5
0x200FFFFE
0x20000002
4
4
1MB SRAM bit-band region
3
3
0x23FFFFF0
0x22000010
32MB alias region
2
2
1
1
0
0
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
11011A–ATARM–04-Oct-10
3
3
0x23FFFFE0
0x22000000
2
2
1
1
0
0