18.4.3.2 Intellectual Property Protection

The DSU provides the Debug Access Level (DAL) mechanism, which disables or limits debugger access to the device. Refer to the Debugger Access Level (DAL) section in the BootROM - Boot ROM chapter for more information about how the DAL value is determined.

If the debugger attempts to access a device region that is not permitted by the current DAL setting, the DAP Security filter will block the access and return an error to the Arm AHB-AP hardware, resulting in the assertion of the ARM DP sticky error bit. The DAP Security filter will also block access during system initialization, so a debugger cannot perform unauthorized access until the boot ROM has had time to read and apply the DAL setting.

Some features that are not activated by APB transactions are unavailable when the device is protected: