Arm trace technical specification

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When using the J-Trace PRO as a debugging tool it is crucial for a successful session that the trace data output by the microcontroller is meeting specific timing requirements. The trace clock speed (TRACECLK) is on most microcontrollers directly dependent on the CPU clock speed and is usually half of the CPU clock speed.

Arm trace timing requirements

Arm defines the trace timing requirements as follows:

Trace timing diagram with CPU clock, TRACECLK and Trace data
Timing variables and values
Signal name Description Value
twl TRACECLK LOW pulse width Min. 2 ns
twh TRACECLK HIGH pulse width Min. 2 ns
tr/tf Clock and data rise/fall time Max. 3 ns
ts Data setup time Min. 3 ns
th Data hold time Min. 2 ns

Note: J-Trace PRO has been designed to work with min. 1 ns ts and min. 1 ns th.

According to specification the maximum in spec trace clock is 100 MHz. But as there are some target devices that support even higher trace clock signals than that J-Trace Pro also supports higher trace clock speeds as explained in the note above.

Solution for out of spec signals

In some rare cases devices supporting Embedded Trace Macrocell (ETM) trace are not outputting signals that fulfill the aforementioned timing requirements. To still make trace debugging available to the customer the J-Trace PRO has a so called Trace timing configuration feature which compensates wrongly output trace data signals.

Required trace components

Minimum for buffer trace

Minimum for pin tracing

Optional for both setups

  • Trace funnel

Special case Cortex-M0+ trace