256 Mbit SPI NOR Flash — FL-S series
It uses a Quad I/O SPI interface running at 66 MHz, which gives a practical read throughput high enough for execute-in-place (XIP) code shadowing and OTA staging in embedded systems.
66 MHz Quad I/O — what it buys you
At 66 MHz in Quad I/O mode, the S25FL256SDPMFIG01 can sustain roughly 33 MB/s read throughput (66 MHz × 4 bits per cycle). That is enough to feed a Cortex-M or RISC-V core running from external Flash without stalling on instruction fetches, provided the controller's SPI peripheral can keep up. The 256 Mbit density holds a full firmware image plus a config file or calibration table, with room for a backup slot if you double the footprint. For designs that shadow code into RAM at boot, the 66 MHz clock keeps the copy time under a couple hundred milliseconds.
The FL-S series has a broad density range (from 64 Mbit up to 1 Gbit), so a future migration to a larger or smaller part within the same family keeps the same package and interface — useful if the firmware grows or the BOM needs cost reduction.
16-SOIC footprint — layout notes
The 16-SOIC package (0.295 inch body width, 7.50 mm) is a common NOR Flash footprint shared across the FL-S family and many competitors.