US Patent 7162410 In-circuit emulator with gatekeeper for watchdog timer

A watchdog timer control using a gatekeeper in an In-Circuit Emulation system. The In-Circuit Emulation system has a microcontroller operating in lock-step synchronization with a virtual microcontroller. When a watchdog event occurs, the gatekeeper, forming a part of the virtual microcontroller, crowbars the reset line of the virtual microcontroller as well as the real microcontroller. This freezes the state of the virtual microcontroller so that debug operations can be carried out. The gatekeeper operates with its own gatekeeper clock independent of the microcontroller clock. When a watchdog event occurs, the gatekeeper clock is rerouted to the virtual microcontroller to facilitate debug operations of the virtual microcontroller.