1 Kbit EEPROM with dual-interface flexibility
The Microchip AT21CS01-STUM16-T is a 1 Kbit serial EEPROM that speaks both I²C and a proprietary Single-Wire protocol, packing 128 x 8 organization into a SOT-23-3 package.
Dual-protocol bus — I²C and Single-Wire
The AT21CS01 supports both I²C and a single-pin Single-Wire interface, letting you share the same part across designs that use either bus. On an I²C bus it behaves as a standard slave; in Single-Wire mode it uses only one GPIO and a ground reference, freeing a pin on a cramped MCU. The 125 kbps clock rate is adequate for configuration reads or periodic sensor-log retrieval — not for streaming, but fine for the 128-byte array it manages.
The 1.7 V minimum supply lets it run directly from a Li-ion cell near end-of-discharge without a boost regulator. The 5 ms write cycle is the same for a single byte or a full page — budget that latency in any write-heavy routine.