The MN63121 is a 1K-bit EEPROM supporting serial I/O and operating on a single power supply with a volt- age between 1.8 and 5.5 V. It provides the following pins for easy interfacing to microprocessors or microcontrollers: chip select (CS), serial clock (SCK), data input (DI), data output (DO), reset (RESET), and busy (RDY/BUSY). It includes a built-in timer for use in automatically erasing and writing data during data up- date operations. The memory organization is 64 × 16 bits. The chip in- dicates the end of a write operation with either the RDY/ BUSY pin or the state of the DO pin after the status out- put mode has been set. Conversion of peripheral circuits to CMOS realizes great reductions in power consumption. Use of floating gate memory cells and a built-in error correction circuit ensures reliable operation for 105 write cycles.