SRAM Timekeeper 16K, 48T02, DIP24 - 

The M48T02-150PC1 is a 16kb Non-volatile Static RAM and Real-time Clock which is pin and functional compatible with the DS1642. The M48T02 button cell has sufficient capacity and storage life to maintain data and clock functionality for an accumulated time period of at least 10 years in the absence of power over the operating temperature range. It is a non-volatile pin and function equivalent to any JEDEC standard 2kb x 8 SRAM. It also easily fits into many ROM, EPROM and EEPROM sockets providing the non-volatility of PROMs without any requirement for special write timing or limitations on the number of write that can be performed.