AT21CS01 EEPROM Microchip Technology AT21CS01 EEPROM device is self-powered via 1.7V to 3.6V pull-up voltage in the single I/O line low voltage operation. These AT21CS01 provide 1,024bits of serial EEPROM internally organized as 128 words of 8 bits each (1Kbit). This device shares a common single-wire bus with an I2C protocol structure from which communication is achieved through a single I/O pin. The AT21CS01 features a 15.4Kbps max bit rate in standard speed mode and a 125Kbps max bit rate in high-speed mode.