LM3S2276 Datasheet, PDF (76/785 Pages) Texas Instruments – Stellaris® LM3S2276 Microcontroller

The Cortex-M3 Processor
Table 2-6. SRAM Memory Bit-Banding Regions (continued)
Address Range
Memory Region
0x2200.0000 - 0x23FF.FFFF SRAM bit-band alias
Instruction and Data Accesses
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
Memory Region
Instruction and Data Accesses
0x4000.0000 - 0x400F.FFFF 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.
0x4200.0000 - 0x43FF.FFFF 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 77 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:
0x23FF.FFE0 = 0x2200.0000 + (0x000F.FFFF*32) + (0*4)
■ The alias word at 0x23FF.FFFC maps to bit 7 of the bit-band byte at 0x200F.FFFF:
0x23FF.FFFC = 0x2200.0000 + (0x000F.FFFF*32) + (7*4)
■ The alias word at 0x2200.0000 maps to bit 0 of the bit-band byte at 0x2000.0000:
0x2200.0000 = 0x2200.0000 + (0*32) + (0*4)
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November 17, 2011
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