NXP Semiconductors LPC24XX UM10237 - Manual (Page 744)

UM10237_4 © NXP B.V. 2009. All rights reserved.
User manual Rev. 04 — 26 August 2009 744 of 792
1. Features
• Closely track the instructions that the ARM core is executing.
• One external trigger input.
• 10 pin interface.
• All registers are programmed through JTAG interface.
• Does not consume power when trace is not being used.
• THUMB instruction set support.
2. Applications
As the microcontroller has significant amounts of on-chip memories, it is not possible to
determine how the processor core is operating simply by observing the external pins. The
ETM provides real-time trace capability for deeply embedded processor cores. It outputs
information about processor execution to a trace port. 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.
3. 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 through a narrow trace port. An external
Trace Port Analyzer captures the trace information under software debugger control.
Trace port can broadcast the Instruction trace information. 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. Trace information generation can be controlled by selecting the trigger
resource. Trigger resources include address 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.
3.1 ETM configuration
The following standard configuration is selected for the ETM macrocell.
UM10237
Chapter 34: LPC24XX Embedded Trace Module (ETM)
Rev. 04 — 26 August 2009 User manual
Table 679. ETM configuration
Resource number/type Small [1]
Pairs of address comparators 1
Data Comparators 0 (Data tracing is not supported)
Memory Map Decoders 4
Counters 1
Sequencer Present No