Static information storage and retrieval – Read/write circuit – Simultaneous operations
Patent
1991-02-07
1993-07-06
Fears, Terrell W.
Static information storage and retrieval
Read/write circuit
Simultaneous operations
365200, 365 49, G11C 1300
Patent
active
052260097
ABSTRACT:
A semiconductor memory device includes a dynamic random access memory (DRAM) cell array (300) as a main memory, a static random access memory (SRAM) cell array (310) as a cache memory, and a content addressable memory (CAM) cell array (320) as a tag memory. The SRAM cell array has word lines (SWL) corresponding in number to match detection lines (23-1 to 23-4) of the CAM cell array. The CAM cell array retrieves contents thereof using external row address as retrieval data. When a match is found in the CAM cell array, a match detection signal is supplied to a match detection line for directly driving a corresponding word line in the SRAM cell array. This semiconductor memory device includes circuitry (22, 22') for generating a cache hit/miss indicating signal in response to signal potentials of the word lines of the SRAM cell array. When the cache hit indicating signal is generated, a column address signal selects a column in the SRAM cell array, and access is made to a memory cell at a crossing between the driven row and selected column of the SRAM cell array. When the cache miss indicating signal is generated, access is made to a memory cell selected by the row address and column address in the DRAM cell array through a column in the SRAM cell array, and in addition data is transferred to a block in the SRAM cell array selected by a block selecting signal from a corresponding block in the DRAM cell array. Further, on a cache miss, data transfer is made prior to external access from a block in the SRAM cell array to a corresponding block in the DRAM cell array.
REFERENCES:
patent: 4740971 (1988-04-01), Tam et al.
patent: 4860262 (1989-08-01), Chiu
patent: 5043943 (1991-08-01), Crisp et al.
Fears Terrell W.
Mitsubishi Denki & Kabushiki Kaisha
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