128 Mbit NOR Flash on the Quad SPI bus
The S25FL128SDSMFN000: 80 MHz clock frequency with Quad I/O interface.
80 MHz SPI clock — read margin and timing budget
At 80 MHz the SPI clock period is 12.5 ns. The Quad I/O interface reads four bits per clock, so a single 256-byte page reads in about 6.4 µs after the initial command and address overhead. The 80 MHz rating is the maximum clock frequency; the actual throughput depends on the host controller's SPI peripheral speed and the PCB trace length. Keep the SPI clock trace under 50 mm and match the lengths of the four I/O lines to avoid skew eating into the hold margin. The 16-SOIC package (7.50 mm body width) has a 1.27 mm pin pitch, which gives reasonable room for a four-layer board with a solid ground plane under the Flash.
Industrial temperature grade and deployment context
The 125°C ceiling is the junction temperature limit — derate the read current (typically 25 mA active at 80 MHz) above 105°C ambient if the board has poor airflow. The wide temperature range also simplifies qualification across a product family that ships into both commercial and industrial markets: one BOM line covers both.