The Arm SWD interface is a subset of the JTAG interface, making use of TCK and TMS pins. The Arm JTAG and AVR JTAG connectors are, however, not pin-compatible, so when designing an application PCB, which uses a SAM device with SWD or JTAG interface, it is recommended to use the Arm pinout shown in the figure below. The SAM connector port on the Atmel-ICE can connect directly to this pinout.
Atmel-ICE is capable of streaming UART-format ITM trace to the host computer. Trace is captured on the TRACE/SWO pin of the 10-pin header (JTAG TDO pin). Data is buffered internally on the Atmel-ICE and is sent over the HID interface to the host computer. The maximum reliable data rate is about 3 MB/s.