View ds1312 datasheet:

DS1312 Nonvolatile Controller with Lithium Battery Monitor www.dalsemi.com FEATURES PIN ASSIGNMENT Converts CMOS SRAM into nonvolatile memory VCCO 1 8 VCCI VCCO 1 8 VCCI VBAT 2 7 BW VBAT 2 7 BW Unconditionally write-protects SRAM when TOL 3 6 CEO TOL 3 6 CEO VCC is out of tolerance 5 5 GND 4 CEI GND 4 CEI Automatically switches to battery backup supply when VCC power failure occurs DS1312 8-Pin DIP DS1312S-2 8-Pin SOIC (300-mil) (150-mil) Monitors voltage of a lithium cell and provides advanced warning of impending NC 1 20 NC NC 1 16 NC battery failure VCCO 2 19 VCCI VCCO 2 15 VCCI Signals low-battery condition on active low NC 3 18 RST NC 3 14 RST 17 VBAT 4 NC VBAT 4 13 NC Battery Warning output signal NC 5 16 NC NC 5 12 BW Optional -5% or -10% power-f