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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
539 of 571
1.
How to read this chapter
The contents of this chapter apply to all LPC29xx parts.
2.
Features
•
Closely tracks the instructions that the ARM core is executing.
•
On-chip trace data storage (ETB).
•
All registers are programmed through JTAG interface.
•
Does not consume power when trace is not being used.
•
THUMB/Java instruction set support.
3.
Introduction
The ETM provides real-time trace capability for deeply embedded processor cores. It
outputs information about processor execution to a trace buffer. A software debugger
allows configuration of the ETM using a JTAG interface and displays the trace information
that has been captured in a format that a user can easily understand. The ETB stores
trace data produced by the ETM.
4.
Description
The ETM is connected directly to the ARM core and not to the main AMBA system bus. It
compresses the trace information and exports it to a trace buffer. An internal Embedded
Trace Buffer captures the trace information under software debugger control. ETM can
broadcast the Instruction/data trace information. Bytecodes executed while in Java state
can also be traced. The trace contains information about when the ARM core switches
between states. Instruction trace (or PC trace) shows the flow of execution of the
processor and provides a list of all the instructions that were executed. Instruction trace is
significantly compressed by only broadcasting branch addresses as well as a set of status
signals that indicate the pipeline status on a cycle by cycle basis. For data accesses either
data or address or both can be traced. Trace information generation can be controlled by
selecting the trigger resource. Trigger resources include address/data comparators,
counters and sequencers. Since trace information is compressed the software debugger
requires a static image of the code being executed. Self-modifying code can not be traced
because of this restriction.
4.1 ETM9 configuration
The following standard configuration is selected for the ETM9 macrocell.
UM10316
Chapter 31: LPC29xx ETM/ETB interface
Rev. 00.06 — 17 December 2008
User manual