Ther are to debugging conectors in the Arduino Due schematic.
1. 10-pin (referred as JTAG) -> JTAG & Serial Wire (SWJ)
2. 4-pin (referred as DEBUG) -> Specification?
I referred to the 10-pin connector and use the Segger J-Link 9-pin Cortex-M Adapter.
The J-Link 9-pin Cortex-M Adapter allows JTAG, SWD and SWO connections between J-Link and Cortex-M based target hardware systems.
Key pin. Removed from target connector, or physically blocked on debug connector.http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0314h/Chdcdggc.html
and why is this Key pin.(7) not removed from the Arduino Due Board?