Glossary
ARM DDI 0432C Copyright © 2009 ARM Limited. All rights reserved. Glossary-5
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Serial Wire Debug Port (SW-DP)
The interface for Serial Wire Debug.
Serial Wire Debug (SWD)
A debug implementation that uses a serial connection between the SoC and a debugger.
This connection normally requires a bi-directional data signal and a separate clock
signal, rather than the four to six signals required for a JTAG connection.
SWD See Serial Wire Debug.
SW-DP See Serial Wire Debug Port.
TAP See Test Access Port.
Test Access Port (TAP)
The collection of four mandatory terminals and one optional terminal 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.
Thumb instruction A halfword that specifies an operation for an ARM processor in Thumb state to
perform. Thumb instructions must be halfword-aligned.
Thumb state A processor that is executing Thumb (16-bit) halfword aligned instructions is operating
in Thumb state.
Unaligned 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.
Unpredictable For reads, the data returned when reading from this location is unpredictable. It can
have any value. For writes, writing to this location causes unpredictable behavior, or an
unpredictable change in device configuration. Unpredictable instructions must not halt
or hang the processor, or any part of the system.
Watchpoint A watchpoint is a mechanism provided by debuggers to halt program execution when
the data contained by a particular memory address is changed. Watchpoints are inserted
by the programmer to enable inspection of register contents, memory locations, and
variable values when memory is written to test that the program is operating correctly.
Watchpoints are removed after the program is successfully tested. See also Breakpoint.
Word A 32-bit data item.
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