View ds1230w datasheet:

DS1230W 3.3V 256k Nonvolatile SRAM www.maxim-ic.com FEATURES PIN ASSIGNMENT 10 years minimum data retention in the VCC A14 1 28 absence of external power A12 27 WE 2 A7 3 26 A13 Data is automatically protected during power A6 4 25 A8 loss A9 A5 5 24 Replaces 32k x 8 volatile static RAM, A4 6 23 A11 A3 OE EEPROM or Flash memory 7 22 A2 8 21 A10 Unlimited write cycles A1 CE 9 20 Low-power CMOS A0 10 19 DQ7 DQ6 Read and write access times as fast as 100ns DQ0 11 18 12 17 DQ1 DQ5 Lithium energy source is electrically 13 16 DQ2 DQ4 disconnected to retain freshness until power is 14 15 GND DQ3 applied for the first time 28-Pin Encapsulated Package Optional industrial temperature range of 740-Mil Extended -40 C to +85 C, designated IND JEDEC sta