February 2014
34
E
XHIBITION
H
IGHLIGHTS
Of course, the combination of program or
data trace and signal trace from peripherals
provides substantive benefits if a certain event
or interaction between different parts of the
controller is of interest. As an example, with
trace the time an interrupt service requires
from an incoming CAN message to respond
with a signal on an external port pin can now
be easily measured. The on-chip trace recog-
nizes a particular message on the CAN bus –
it is even possible to filter for the origin and
message type – and starts the trace recording.
The write access to the port pin is visible to
the trace unit as well and can be used as an
event to stop the trace. Figure 4 shows the
trace task configured with the graphical editor
of the Universal Emulation Configurator
(UEC). Apart from the time measurement,
the configuration contains the setup for a
complete program and data trace as well. Using
trace based profiling, time consuming se-
quences within the interrupt service routines
can be easily identified (figure 5).
Will signal trace become mainstream? This is
an interesting question. For industrial and au-
tomotive application signal trace is certainly
an important extension to the controller debug
functionality. However, you get these things
only with some investments in hardware and
tools. To keep the hardware costs within limits,
Infineon pursues their concept of two different
controller types: an emulation device with all
the additional hardware for high level debug-
ging and trace, and a production device to be
built in the products only with basic debug
support. Apart from Infineon with its MCDS,
another important player in the area of trace
support for industrial and automotive con-
trollers is the NEXUS forum.
They recognized the need for signal trace too
and extended the new revision of the NEXUS
standard 2012 with a new trace type called in-
circuit trace. The first implementation of that
new trace type can be found in Freescale
Qorivva MPC57xx family. However, in-circuit
trace is only used to capture special counter
values provides by a debug module called the
sequence processing unit. Peripherals are not
connected to the trace system except the GTM,
which is also licensed from Bosch. For signals
and special data of the GTM, vendor-defined
messages intended to capture debug informa-
tion which does not fit in the standard NEXUS
messages are used. Whether Freescale will de-
cide to extend its trace support to the other
peripherals too is at the moment not known.
The coverage of peripherals by the trace system
is certainly an important step forward to fully
testable embedded applications. With that
trace becomes more and more an instrument
for system analysis of complex and complete
systems-on-a-chip, and not only for the cores.
Now the mission for tool vendors, like PLS, is
to provide software tools such as the Universal
Emulation Configurator which allow to fully
utilize the trace features and to unrestrictedly
define tailor-made measurement tasks.
Figure 4. Trace task for the CAN peripheral
Figure 5. Function profiling
