The MPS E2PROM is an attractive alternative to the 'add-on' parallel or serial nonvolatile memories that have traditionally been used in microcontroller-based systems. It features serial E2PROM memory that is accessed via a standard parallel bus. The serial architecture of the X84161/641/129 provides a cost and space saving replacement for low density parallel devices. Its unique parallel bus compatible interface also offers an I/O-saving alternative to serial devices that typically require two or three control pins for communication purposes. Although the X84161/641/129 can be used to interface with practically any 8, 16, or 32-bit microcontroller, the code provided here is for the widely used 8051 family.