A 28 nm Configurable Memory (TCAM/BCAM/SRAM) Using Push-Rule 6T Bit Cell Enabling Logic-in-Memory

Conventional content addressable memory (BCAM and TCAM) uses specialized 10T/16T bit cells that are significantly larger than 6T SRAM cells. A new BCAM/TCAM is proposed that can operate with standard push-rule 6T SRAM cells, reducing array area by 2-5x and allowing reconfiguration of the SRAM as a CAM. In this way, chip area and overall capacitance can be reduced, leading to higher energy efficiency for search operations. In addition, the configurable memory can perform bit-wise logical operations: AND and NOR on two or more words stored within the array. Thus, the configurable memory with CAM and logical function capability can be used to off-load specific computational operations to the memory, improving system performance and efficiency. Using a 6T 28 nm FDSOI SRAM bit cell, the 64x64 (4 kb) BCAM achieves 370 MHz at 1 V and consumes 0.6 fJ/search/bit. A logical operation between two 64 bit words achieves 787 MHz at 1 V.