DS1557

19-5501; Rev 9/10 www.maxim-ic.com DS1557 4Meg, Nonvolatile, Y2K-Compliant Timekeeping RAM FEATURES  Integrated NV SRAM, Real-Time Clock (RTC), Crystal, Power-Fail Control Circuit, and Lithium Energy Source  Clock Registers are Accessed Identically to the Static RAM; These Registers Reside in the 16 Top RAM Locations  Century Byte Register (i.e., Y2K Compliant)  Totally Nonvolatile with Over 10 Years of Operation in the Absence of Power  Precision Power-On Reset  Programmable Watchdog Timer and RTC Alarm  BCD-Coded Year, Month, Date, Day, Hours, Minutes, and Seconds with Automatic Leap Year Compensation Valid Up to the Year 2100  Battery Voltage-Level Indicator Flag  Power-Fail Write Protection Allows for 10% VCC Power-Supply Tolerance  Lithium Energy Source is Electrically Disconnected to Retain Freshness Until Power is Applied for the First Time  Also Available in Industrial Temperature Range: -40°C to +85°C PIN CONFIGURATION TOP VIEW IRQ/FT 1 34 A18 A15 2 Maxim 33 A17 A16 3 RST 4 VCC WE 5 6 DS1557 32 A14 31 30 A13 A12 29 A11 OE CE DQ7 DQ6 DQ5 DQ4 DQ3 DQ2 DQ1 DQ0 GND 7 28 8 27 9 26 10 25 11 24 12 23 13 22 14 21 15 20 16 17 X1 GND VBAT X2 19 18 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0 PowerCap Module Board (Uses DS9034PCX PowerCap) PIN DESCRIPTION A0–A18 - Address Input DQ0–DQ7 IRQ/FT - Data Input/Outputs - Interrupt, Frequency Test Output (Open Drain) RST - Power-On Reset Output (Open Drain) CE - Chip Enable OE...