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12 Trace Port Interface Unit (TPIU)

The EM35x integrates the standard ARM® Trace Port Interface Unit (TPIU). The TPIU receives a data stream

from the on-chip trace data generated by the standard ARM® Instrument Trace Macrocell (ITM), buffers the

data in a FIFO, formats the data, and serializes the data to be sent off chip through alternate functions of the

GPIO. Since the primary function of the TPIU is to provide a bridge between on-chip ARM system debug

components and external GPIO, the TPIU itself does not generate data. Figure 12-1 illustrates the three

primary components of the TPIU.

Figure 12-1. TPIU Block Diagram

The TPIU is comprised of:

Asynchronous FIFO: The asynchronous FIFO receives a data stream generated by the ITM and enables the

trace data to be sent off chip at a speed that is not dependent on the speed of the data source.

Formatter: The formatter inserts source ID signals into the data packet stream so that trace data can be

re-associated with its trace source. Since the EM35x has only one trace source, the ITM, it is not necessary

to use the formatter and therefore the formatter only adds overhead into the data stream. Since certain

modes of the TPIU automatically enable the formatter, these modes should be avoided whenever possible.

Trace Out: The trace out block serializes the data and sends it off chip via the proper alternate output

GPIO functions.

The five pins available to the TPIU are:

SWO

TRACECLK

TRACEDATA0

TRACEDATA1

TRACEDATA2

TRACEDATA3

Since these pins are alternate outputs of GPIO, refer to Chapter 1, Pin Assignments and Chapter 7, GPIO for

complete pin descriptions and configurations.

Note:

The SWO alternate output is mirrored on GPIO PC1 and PC2.

Note:

GPIO PC1 shares both the SWO and TRACEDATA0 alternate outputs. This is possible because SWO and

TRACEDATA0 are mutually exclusive and only one may be selected at a time in the trace out block.

The Ember software utilizes the TPIU for efficiently outputting debug data. Altering the TPIU configuration

may conflict with Ember debug output.

For further information on the TPIU, contact Ember support for the ARM® CortexTM-M3 Technical Reference

Manual, the ARM® CoreSightTM Components Technical Reference Manual, the ARM® v7-M Architecture

Reference Manual, and the ARM® v7-M Architecture Application Level Reference Manual.

12-1

120-035X-000D

Preliminary

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