National Semiconductor Corporation

Dan Craig O'Neill

Robert James Divivier

Michael John Shay

William V Miller

Daniel Ross Herrington

Kent Bruce Waterson

Alexander Perez

Jianhua Helen Pang

Ralph Warren Haines

James Andrew Colgan

David Scott Weinman

Stephen C Pries

John R Gunther

Brian J Marley

An integrated circuit (IC) includes multiple circuits and functions which share multiple internal signal buses, three physical and five logical, according to distributed bus access and control arbitration. The multiple internal signal buses are shared among three tiers of internal circuit functions: a central processing unit and a DMA controller; a DRAM controller and a bus interface unit; and peripheral interface circuits, such as PCMCIA and display controllers. Two of the physical buses correspond to two of the logical buses and are used for communications within the IC. The third physical bus corresponds to three of the logical buses and is used for communications between the IC and circuits external to the IC. Arbitration for accessing and controlling the various signal buses is distributed both within and among the three tiers of internal circuit functions. Maximum performance is thereby achieved from the circuit functions accessed most frequently, while still achieving high performance from those circuit functions accessed less frequently. The IC may provided with a processor core with features that support In-Circuit Emulation (ICE).

Integrated circuit with multiple functions sharing multiple internal

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San Carlos, CA, United States of America

Dan Craig O'Neill