ARM DUI 0553A Copyright © 2010 ARM. All rights reserved. Glossary-1
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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 address calculation for the instruction. 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.
Big-endian (BE) Byte ordering scheme in which bytes of decreasing significance in a data word are stored at
increasing addresses in memory.
See also Byte-invariant, Endianness, Little-endian (LE).
Big-endian memory Memory in which:
• a byte or halfword at a word-aligned address is the most significant byte or halfword within
the word at that address
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