ARM ARM7TDMI - Page 279

Glossary
ARM DDI 0210C Copyright © 2001, 2004 ARM Limited. All rights reserved. Glossary-3
In-circuit emulator An In-Circuit Emulator (ICE), is a device that aids the debugging of hardware and
software. Debuggable ARM processors such as the ARM7TDMI have extra hardware
called EmbeddedICE to assist this process.
See also EmbeddedICE.
IRQ Interrupt request.
Joint Test Action Group
The name of the organization that developed standard IEEE 1149.1. This standard
defines a boundary-scan architecture used for in-circuit testing of integrated circuit
devices.
JTAG See Joint Test Action Group.
Link register This register holds the address of the next instruction after a branch with link
instruction.
Little-endian memory
Memory organization where the most significant byte of a word is at a higher address
than the least significant byte.
LR See Link register
Macrocell A complex logic block with a defined interface and behavior. A typical VLSI system
will comprise several macrocells (such as an ARM7TDMI, an ETM7, and a memory
block) plus application-specific logic.
Memory Management Unit
Allows control of a memory system. Most of the control is provided through translation
tables held in memory. The ARM7TDMI processor does not include a memory
management unit, but you can add one if required.
MMU See Memory Management Unit
PC See Program Counter.
Privileged mode Any processor mode other than User mode. Memory systems typically check memory
accesses from privileged modes against supervisor access permissions rather than the
more restrictive user access permissions. The use of some instructions is also restricted
to privileged modes.
Processor Status Register
See Program Status Register
Program Counter Register 15, the Program Counter, is used in most instructions as a pointer to the
instruction that is two instructions after the current instruction.