Functional Description
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SWRU543–January 2019
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Copyright © 2019, Texas Instruments Incorporated
Cortex
®
-M4 Processor
2.2.3.1 Bit-Banding
A bit-band region maps each word in a bit-band alias region to a single bit in the bit-band region. In Arm
®
Cortex
®
-M4 architecture, the bit-band regions occupy the lowest 1MB of the SRAM. Accesses to the 32-
MB SRAM alias region map to the 1-MB SRAM bit-band region, as shown in Table 2-5.
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.
The CC32xx family of Wi-Fi microcontrollers support up to 256KB of on-chip SRAM for code and data.
The SRAM starts from address 0x2000 0000.
Bit-banding for peripherals is not supported in the CC32xx.
Table 2-5. SRAM Memory Bit-Banding Regions
Address Range Memory Region Instruction and Data Accesses
Start End
0x2000.0000 0x2003.FFFF 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.
0x2200.0000 0x23FF.FFFF 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.
2.2.3.1.1 Directly Accessing an Alias Region
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 targeted bit in the
bit-band region. Writing a value with bit 0 set writes 1 to the bit-band bit, and writing a value with bit 0
clear writes 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.
When reading a word in the alias region, 0x0000 0000 indicates that the targeted bit in the bit-band region
is clear, and 0x0000 0001 indicates that the targeted bit in the bit-band region is set.
2.2.3.1.2 Directly Accessing a Bit-Band Region
Behavior of memory accesses describes the behavior of direct byte, halfword, or word accesses to the bit-
band regions.
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