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ManualsBrandsMICROCHIP TECHNOLOGY ManualsMicrocontrollers, Microprocessors & QuartzesEmbedded microcontroller LQFP 64 (10x10) 32-Bit 120 MHz I/O number 47
61626364656667686970
70
SAM4S Series [DATASHEET]
11100F–ATARM–29-Jan-14
Figure 12-4. Bit-band Mapping
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 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
.
Reading a word in the alias region:
0x00000000 indicates that the targeted bit in the bit-band region is set to 0
0x00000001 indicates that the targeted bit in the bit-band region is set to 1
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.
12.4.2.6 Memory Endianness
The processor views memory as a linear collection of bytes numbered in ascending order from zero. For example, bytes
0–3 hold the first stored word, and bytes 4–7 hold the second stored word. “Little-endian Format”
describes how words
of data are stored in memory.
Little-endian Format
In little-endian format, the processor stores the least significant byte of a word at the lowest-numbered byte, and the most
significant byte at the highest-numbered byte. For example: