
EM358x
244
Rev. 0.4
12 Trace Port Interface Unit (TPIU)
The EM358x 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) and ARM
®
Embedded Trace Macrocell (ETM), buffers the data in a FIFO for the ITM and FIFO for the ETM, 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 composed of:
Two asynchronous FIFOs: The asynchronous FIFOs receive a data stream generated by the ITM and ETM
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.
Trace Out: The trace out block serializes the data and sends it off chip by 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 7, GPIO, and in the
Ember EM358x Data Sheet
,
Chapter 6, Pin Assignments, 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 customer support for the ARM
®
Cortex
TM
-M3 Technical Reference
Manual, the ARM
®
CoreSight
TM
Components Technical Reference Manual, the ARM
®
v7-M Architecture
Reference Manual, and the ARM
®
v7-M Architecture Application Level Reference Manual.
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