Memory Model
103
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Cortex
®
-M4F Processor
Table 1-18. Peripheral Memory Bit-Banding Regions (continued)
Address Range
Memory Region
Instruction and Data Accesses
Start
End
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 × 32) + (bit_number × 4)
bit_word_addr = bit_ban 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.
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)
•
The alias word at 0x2200.001C maps to bit 7 of the bit-band byte at 0x2000.0000:
0x2200.001C = 0x2200.0000+ (0 × 32) + (7 × 4)
Figure 1-14. Bit-Band Mapping