View ds1270ab datasheet:

DS1270Y/AB DS1270Y/AB 16M Nonvolatile SRAM FEATURES PIN ASSIGNMENT • 5 years minimum data retention in the absence of NC 1 36 VCC external power A20 2 35 A19 • Data is automatically protected during power loss A18 3 34 NC • Unlimited write cycles A16 4 33 A15 • Low–power CMOS operation A14 5 32 A17 A12 6 31 WE • Read and write access times as fast as 70 ns A7 7 30 A13 • Lithium energy source is electrically disconnected to A6 8 29 A8 retain freshness until power is applied for the first time A5 9 28 A9 • Full ±10% VCC operating range (DS1270Y) A4 10 27 A11 A3 11 26 OE • Optional ±5% VCC operating range (DS1270AB) A2 12 25 A10 • Optional industrial temperature range of –40°C to A1 13 24 CE +85°C, designated IND A0 14 23 DQ7 DQ0 15 22 DQ6 DQ1 16 21 DQ5 DQ2 17 2