A memory controller has an asynchronous portion and a synchronous portion. The synchronous portion is used when the system processor is accessing the memory, while the asynchronous portion is used when control of the memories is held by a DMA controller or a bus master located on a standardized bus....http://www.google.fr/patents/US5218686?utm_source=gb-gplus-shareBrevet US5218686 - Combined synchronous and asynchronous memory controller
Combined synchronous and asynchronous memory controller
