16.7.1 Principle of Operation

The DSU monitors the presence of a debugger to control appropriately on-chip resources when a debugger is attached to the device. The following are two attachment methods with different properties discussed later:

• Cold-plugging: Attachment when external reset is asserted.
• Hot-plugging: Attachment when external reset is not asserted.

A debugger presence has several effects on the device:

• Assigns JTAG or SWD pads to the Debug Port (DP) by controlling the port mux
• Enables Access Ports
• Extends the device CPUs reset phases

The DSU also implements Boot Communication Channels to enable communication with the device’s Boot ROM. For additional information on the Arm debug components, refer to the Arm “Debug Interface v5 Architecture Specification” document.