Datasheet

SAM3X / SAM3A [DATASHEET]
Atmel-11057C-ATARM-SAM3X-SAM3A-Datasheet_23-Mar-15
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10.24 Glossary
This glossary describes some of the terms used in technical documents from ARM.
Abort
A mechanism that indicates to a processor that the value associated with a memory access is invalid. An abort can
be caused by the external or internal memory system as a result of attempting to access invalid instruction or data
memory.
Aligned
A data item stored at an address that is divisible by the number of bytes that defines the data size is said to be
aligned. Aligned words and halfwords have addresses that are divisible by four and two respectively. The terms
word-aligned and halfword-aligned therefore stipulate addresses that are divisible by four and two respectively.
Banked register
A register that has multiple physical copies, where the state of the processor determines which copy is used. The
Stack Pointer, SP (R13) is a banked register.
Base register
In instruction descriptions, a register specified by a load or store instruction that is used to hold the base value for
the instruction’s address calculation. Depending on the instruction and its addressing mode, an offset can be
added to or subtracted from the base register value to form the address that is sent to memory.
See also “Index register”
Breakpoint
A breakpoint is a mechanism provided by debuggers to identify an instruction at which program execution is to be
halted. Breakpoints are inserted by the programmer to enable inspection of register contents, memory locations,
variable values at fixed points in the program execution to test that the program is operating correctly. Breakpoints
are removed after the program is successfully tested.
Condition field
A four-bit field in an instruction that specifies a condition under which the instruction can execute.
Conditional execution
If the condition code flags indicate that the corresponding condition is true when the instruction starts executing, it
executes normally. Otherwise, the instruction does nothing.
Context
The environment that each process operates in for a multitasking operating system. In ARM processors, this is
limited to mean the physical address range that it can access in memory and the associated memory access
permissions.
Coprocessor
A processor that supplements the main processor. Cortex-M3 does not support any coprocessors.
Debugger
A debugging system that includes a program, used to detect, locate, and correct software faults, together with
custom hardware that supports software debugging.
Direct Memory Access (DMA)
An operation that accesses main memory directly, without the processor performing any accesses to the data
concerned.