COMMUNICATION INTERFACE FOR DIAGNOSTIC CIRCUITS OF AN INTEGRATED CIRCUIT

摘要

An integrated circuit is provided with diagnostic circuitry, such as serial scan chains or debug bus access circuits, with which communication is established using an interface circuit coupled with a bi-directional serial link to an external diagnostic device. The bi-directional serial link carries both data and control signals. The serial protocol can include provision for a pacing signal whereby the diagnostic circuitry can indicate to the external diagnostic device when it is ready to receive more data and/or when it has completed a particular diagnostic operation. This self-pacing ability is strongly advantageous. A training signal generated by the external diagnostic device may be detected by the interface circuit on initialisation and used to derive sampling point timings. Thus, the need to provide a separate clock signal can in such circumstances be avoided.