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Philips Semiconductors
ARM-based Microcontroller
22. EMBEDDED TRACE MACROCELL
FEATURES
• Closely track the instructions that the ARM core is executing
• 10 pin interface
• 1 External trigger input
• All registers are programmed through JTAG interface
• Does not consume power when trace is not being used
• THUMB instruction set support
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.
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.
ETM Configuration
The following standard configuration is selected for the ETM macrocell.
Table 225: ETM Configuration
Pairs of address comparators
Data Comparators
Memory Map Decoders
Counters
Sequencer Present
External Inputs
Embedded Trace Macrocell
Resource number/type
LPC2119/2129/2194/2292/2294
0 (Data tracing is not supported)
290
Preliminary User Manual
1
Small
1
4
1
No
2
May 03, 2004
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