256 Mbit NOR Flash on the Quad SPI bus
The S25FL256LDPNFV013: It speaks SPI with Quad I/O and QPI support, clocked at 66 MHz. That Quad SPI interface means you can read four bits per clock cycle, so the effective throughput for code shadowing or data logging is well above what a single-bit SPI part delivers at the same frequency. The supply range spans 2.7V to 3.6V, which lets it run straight off a 3.3V rail without an extra regulator.
Surface-mount only, so no socket option for prototyping — plan for a rework station if you need to swap it during debug.