15 ns dual-port SRAM — the bus-timing anchor
The Cypress CY7C0251-15AC is a 144 Kbit (8K x 18) dual-port asynchronous SRAM with a 15 ns access time, designed for systems where two independent buses need simultaneous read/write access to a shared memory array. The dual-port architecture eliminates the arbitration overhead of a single-port SRAM with external muxing — each port has its own address, data, and control lines, so a processor and a DSP (or two processors) can access the same memory location without dead cycles.
Package and footprint — 100-TQFP, 14x14 mm
The part comes in a 100-LQFP package (also specified as 100-TQFP, 14x14 mm body). The 0.5 mm pitch requires a controlled-impedance PCB stack-up for the address and data lines if the bus runs near the 15 ns access limit. Decouple each VDD pin with a 100 nF ceramic placed within 2 mm of the pin; a 10 µF bulk cap per side of the package handles the switching transient when both ports access the same row.