SAM4N_14 Datasheet, PDF (235/795 Pages) ATMEL Corporation – ARM-based Flash MCU

Little-endian memory
Memory in which:
a byte or halfword at a word-aligned address is the least significant byte or halfword within the word at
that address,
a byte at a halfword-aligned address is the least significant byte within the halfword at that address.
See also “Big-endian memory” .
Load/store architecture
A processor architecture where data-processing operations only operate on register contents, not
directly on memory contents.
Memory Protection Unit
(MPU)
Prefetching
Hardware that controls access permissions to blocks of memory. An MPU does not perform any
address translation.
In pipelined processors, the process of fetching instructions from memory to fill up the pipeline before
the preceding instructions have finished executing. Prefetching an instruction does not mean that the
instruction has to be executed.
Preserved
Read
Region
Reserved
Preserved by writing the same value back that has been previously read from the same field on the
same processor.
Reads are defined as memory operations that have the semantics of a load. Reads include the Thumb
instructions LDM, LDR, LDRSH, LDRH, LDRSB, LDRB, and POP.
A partition of memory space.
A field in a control register or instruction format is reserved if the field is to be defined by the
implementation, or produces Unpredictable results if the contents of the field are not zero. These fields
are reserved for use in future extensions of the architecture or are implementation-specific. All
reserved bits not used by the implementation must be written as 0 and read as 0.
Thread-safe
Thumb instruction
Unaligned
In a multi-tasking environment, thread-safe functions use safeguard mechanisms when accessing
shared resources, to ensure correct operation without the risk of shared access conflicts.
One or two halfwords that specify an operation for a processor to perform. Thumb instructions must be
halfword-aligned.
A data item stored at an address that is not divisible by the number of bytes that defines the data size
is said to be unaligned. For example, a word stored at an address that is not divisible by four.
SAM4N Series [DATASHEET]
11158A–ATARM–07-Jun-13
235