LM3S101 Datasheet, PDF (60/445 Pages) List of Unclassifed Manufacturers – Microcontroller

The Cortex-M3 Processor
Note: A word access to the SRAM or the peripheral bit-band alias region maps to a single bit in
the SRAM or peripheral bit-band region.
A word access to a bit band address results in a word access to the underlying memory,
and similarly for halfword and byte accesses. This allows bit band accesses to match the
access requirements of the underlying peripheral.
Table 2-6. SRAM Memory Bit-Banding Regions
Address Range
Start
0x2000.0000
End
0x2000.07FF
0x2200.0000
0x2200.FFFF
Memory Region
Instruction and Data Accesses
SRAM bit-band region Direct accesses to this memory range behave as SRAM
memory accesses, but this region is also bit addressable
through bit-band alias.
SRAM bit-band alias Data accesses to this region are remapped to bit band
region. A write operation is performed as
read-modify-write. Instruction accesses are not remapped.
Table 2-7. Peripheral Memory Bit-Banding Regions
Address Range
Start
0x4000.0000
End
0x400F.FFFF
0x4200.0000
0x43FF.FFFF
Memory Region
Instruction and Data Accesses
Peripheral bit-band
region
Direct accesses to this memory range behave as
peripheral memory accesses, but this region is also bit
addressable through bit-band alias.
Peripheral bit-band alias Data accesses to this region are remapped to bit band
region. A write operation is performed as
read-modify-write. Instruction accesses are not permitted.
The following formula shows how the alias region maps onto the bit-band region:
bit_word_offset = (byte_offset x 32) + (bit_number x 4)
bit_word_addr = bit_band_base + bit_word_offset
where:
bit_word_offset
The position of the target bit in the bit-band memory region.
bit_word_addr
The address of the word in the alias memory region that maps to the targeted bit.
bit_band_base
The starting address of the alias region.
byte_offset
The number of the byte in the bit-band region that contains the targeted bit.
bit_number
The bit position, 0-7, of the targeted bit.
Figure 2-4 on page 61 shows examples of bit-band mapping between the SRAM bit-band alias
region and the SRAM bit-band region:
■ The alias word at 0x23FF.FFE0 maps to bit 0 of the bit-band byte at 0x200F.FFFF:
60
July 14, 2014
Texas Instruments-Production Data