1. An integrated circuit comprising: at least one processor core; and a Known Good Code (KGC) source configured to supply KGC to the processor core for execution, wherein the KGC is protected from modification in the integrated circuit and is provided from an authenticated entity, wherein the KGC comprises a device manager and emulation code, wherein the emulation code emulates at least one second circuit when executed by the processor core, and wherein the device manager, when executed in response to an access attempt to the second circuit from the at least one processor core, determines whether or not the second circuit is included in the integrated circuit and, responsive to determining that the second circuit is included, determines whether or not the second circuit is busy; and the device manager, when executed, grants access to the second circuit responsive to the second circuit being included in the integrated circuit and being not busy at a time that the at least one processor core performs the access attempt; and the emulation code is executed to emulate the at least one second circuit responsive to the at least one second circuit being included in the integrated circuit and being busy at that time that the at least one processor core performs the access attempt; and the emulation code is executed to emulate the at least one second circuit responsive to the at least one second circuit being not included in the integrated circuit.