High-Density 4 Mbit SPI F-RAM with Industrial Qualification and Wide Operating Range The CY15B104Q-SXI is a 4-Mbit (512 K × 8) serial SPI F-RAM providing high-endurance nonvolatile memory with 100 trillion read/write cycles and 151-year data retention at 65°C. Operating from 2.0 V to 3.6 V and supporting up to 40 MHz SPI clock, it enables NoDelay™ writes at bus speed without polling.