A 500-MHz, 32-word/spl times/64-bit, eight-port self-resetting CMOS register file

A two-write-port, six-read-port, 32/spl times/64-bit register file has been designed for 2.5-V 0.5-/spl mu/m CMOS technology, using primary self-resetting CMOS (SRCMOS) circuit techniques. The register cell are completely level-sensitive scan design test compatible. The fabricated register file occupies an area of 1.84/spl times/1.55 mm/sup 2/, and the cell size is 21.6/spl times/30 /spl mu/m/sup 2/. The high-performance register file is implemented in a multiblock structure consisting of subarrays and associated multiplexing circuits. For a given read port, the outputs of all multiplexer circuits are dotted together to form a single global output. A quasi-global approach is used for reset pulse generation and timing control circuits to reduce area overhead. The output pulse width is controlled by a chopper circuit. The write-port operation is achieved by the combination of static data input and dynamic control circuits. The write-path circuits employ the advantages of the input isolation technique. Individual write-enable pulses applied to respective input ports of a multiport register-file cell are effective to establish a priority among those input ports. The present design provides an effective input isolation/decoupling circuit technique that allows the input pulse widths to vary over a wide range. This allows the write operation to be insensitive to control pulse widths, resulting in an effective input isolation scheme. Testing has shown all eight ports to be functional. The measured read access time was 1.1 ns, and read operation has been obtained at cycle times as short as 1.9 ns. The register file has been shown to be tolerant to a very wide range of input pulse widths yet delivers tightly controlled outputs.