256 Kbit SPI EEPROM for configuration storage
The Microchip AT25256B-SSHL-T is a 256 Kbit serial EEPROM with an SPI interface, organized as 32K x 8 bits. This part is commonly used for parameter storage, firmware calibration tables, and configuration data in embedded systems where non-volatile memory with low pin count is required.
At 20 MHz SPI clock, a sequential read of the full 256 Kbit array takes roughly 1.6 ms at the bus level, not counting command overhead.
At 3.3V it is compatible with common MCU SPI peripherals; at 5V it can interface directly with legacy 5V controllers or industrial logic. The wide range also accommodates battery-powered designs that drop below 3V near end-of-discharge.
For dual-sourcing or higher-density requirements, the AT25512-TH-T (512 Kbit, same SPI interface and package) is a functional alternative — though verify the pin-compatible footprint as the TH-T suffix may indicate a different tape/reel orientation.