User guide

Glossary
ARM DDI 0337I Copyright © 2005-2008, 2010 ARM Limited. All rights reserved. Glossary-8
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Prefetch Abort An indication from a memory system to the core that an instruction has been fetched from an
illegal memory location. An exception must be taken if the processor attempts to execute the
instruction. A Prefetch Abort can be caused by the external or internal memory system as a
result of attempting to access invalid instruction memory.
See also Data Abort, Abort.
Prefetch Unit (PFU) The PFU fetches instructions from the memory system that can supply one word each cycle. The
PFU buffers up to three word fetches in its FIFO, which means that it can buffer up to three
32-bit Thumb instructions or six 16-bit Thumb instructions.
Private Peripheral Bus
Memory space at 0xE0000000 to 0xE00FFFFF .
Processor A processor is the circuitry in a computer system required to process data using the computer
instructions. It is an abbreviation of microprocessor. A clock source, power supplies, and main
memory are also required to create a minimum complete working computer system.
RW1C Register bits marked RW1C can be read normally and support write-one-to-clear. A read then
write of the result back to the register will clear all bits set. RW1C protects against
read-modify-write errors occurring on bits set between reading the register and writing the value
back (since they are written as zero, they will not be cleared).
RealView ICE A system for debugging embedded processor cores using a JTAG interface.
Reserved 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.
Scan chain A scan chain is made up of serially-connected devices that implement boundary scan technology
using a standard JTAG TAP interface. Each device contains at least one TAP controller
containing shift registers that form the chain connected between TDI and TDO, through which
test data is shifted. Processors can contain several shift registers to enable you to access selected
parts of the device.
Serial-Wire Debug Port
An optional external interface for the DAP that provides a serial-wire bidirectional debug
interface.
Serial-Wire JTAG
Debug Port
A standard debug port that combines JTAG-DP and SW-DP.
SW-DP See Serial-Wire Debug Port.
SWJ-DP See Serial-Wire JTAG Debug Port.
Synchronization primitive
The memory synchronization primitive instructions are those instructions that are used to ensure
memory synchronization. That is, the LDREX and STREX instructions.
System memory Memory space at 0x20000000 to 0xFFFFFFFF , excluding PPB space at 0xE0000000 to 0xE00FFFFF .
TAP See Test access port.
Test Access Port (TAP)
The collection of four mandatory and one optional terminals that form the input/output and
control interface to a JTAG boundary-scan architecture. The mandatory terminals are TDI,
TDO, TMS, and TCK. The optional terminal is TRST. This signal is mandatory in ARM cores
because it is used to reset the debug logic.