The debug subsystem implements two IEEE standards for debug and test purposes:

IEEE 1149.7 Class 4: Reduced-pin and Enhanced-functionality Test Access Port and Boundary-scan Architecture. This is known by the acronym cJTAG (compact JTAG) and this device uses only two pins to communicate to the target: TMS (JTAG_TMSC) and TCK (JTAG_TCKC). This is the default mode of operation.

IEEE standard 1149.1: Test Access Port and Boundary Scan Architecture Test Access Port (TAP). This standard is known by the acronym JTAG and this device uses four pins to communicate to the target: TMS (JTAG_TMSC), TCK (JTAG_TCKC), TDI (JTAG_TDI) and TDO (JTAG_TDO).

The debug subsystem also implements a user-configurable firewall to control unauthorized access to debug/test ports.