Dallas Semiconductor

DS1221 - Nonvolatile Controller X 4 Chip

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Features Control Circuitry to Make CMOS RAM Nonvolatile Controls up to 4 memories Monitors Vcc and write-protects when out of tolerance Consumes less than 100nA battery current Tests battery condition on power-up Supports redundant batteries

Pin Description Pin Number Description 1 Vcco - RAM Supply 2 Vbat1 - + Battery 1 3 RST - Reset 4 A - Address Input A 5 B - Address Input A 6 RD - Read Input 7 WE - Write Enable 8 GND - Ground 9 D/Q - Data Input/Output 10 CE3 - Chip Enable Output 3 11 CE2 - Chip Enable Output 2 12 CE1 - Chip Enable Output 1 13 CE0 - Chip Enable Output 0 14 CE - Chip Enable Input 15 Vbat2 - + Battery 2 16 Vcci - +5V Supply

Dimensional Drawing Dimensional Drawing

Technical Data Data Sheet Dallas Semiconductor - Data Sheet for DS1221 Application Notes