Introduction
QT
RACE
-
U
SER
M
ANUAL
© 2018 PDQLogic Ltd.
QTrace User Manual Rev 1.01
Page 8
1.7
Target connection
Below are the pin assignments for the ARM Cortex-M 20 pin trace connector. It has a 0.05" pitch and
provides access to the 4-bit ETM interface and JTAG / SWD signals.
Figure 3 Pin assignments of the ARM Cortex-M 20 pin trace connector
1.8
Recommendations for PCB layout of Trace Signals
A good PCB layout for the trace signals is crucial for reliable operation. Below are some
recommendations for PCB layout of the trace signals:
Place the trace connector close to the processor pins
Add 0402 series termination resistors e.g. 22R next to the processor trace pins
Use low capacitance ESD diodes on the trace signals and place them close to the trace
connector
Keep tracks the same length
Do not insert vias
Route all tracks over an unbroken ground plane which is on the first inner layer (the FR4
laminate thickness between the top and ground plane layers should typically be 5 mil)
Figure 4 shows an example of trace signal routing on the STM32-EVAL demonstrator PCB (see Appendix
B STM32-Eval Demonstrator. The trace signals are highlighted in red and the component outlines of
the 0402 series resistors and ESD diodes are highlighted in yellow.
Figure 4 Example trace schematic and PCB signal routing