Integrated Device Technology, Inc.

De H Nguyen

Raymond M Chu

A circuit and method for reading and writing to a microprocessor's internal cache memory during a test mode of operation. During write accesses, an external data bus transmits to an internal data bus an address, cache tags and data in accordance with an external clock. During read accesses, the external data bus transmits an address and receives from the internal data bus data and cache tags. In one embodiment, during a write access, the external data bus is time-multiplexed to transmit an address, cache tags and data in two clock periods of the external clock the external data bus is time-multiplexed to transmit to the internal data bus an address in the first clock period of the external clock signal and to receive tag and data in the next successive clock periods of the external clock signal. In this embodiment, reserved pins are used to specify a cache access mode, including a test mode of operation. During the test mode, read and write buffers for the internal cache are deselected from the interal bus and the central processing unit of the microprocessor is stalled. Control for the cache access is provided via pins which are used during functional (non-test mode) operation to receive external interrupt signals.

Test mode accessing of an internal cache memory

A method and structure for logically disconnecting an on-chip virtual-to-physical address translation unit from a microprocessor by holding the dynamic circuits of the translation unit in precharged state. In one embodiment, the method and structure provide a fixed remapping for the virtual address. A powering down of the translation unit effects power savings when the translation unit is not required.

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Milpitas, CA, United States of America

De H Nguyen