The DS1211 Nonvolatile Controller x8 Chip performs five circuit functions required to render standard CMOS RAM nonvolatile: * Monitor Vcc using a precise comparator that detects power-fail and inhibits chip-enable * Monitor battery status and warn the processor of low status * Switch power between a battery and Vcc, whichever is greater * Write-protect data * Provide for automatically switching between two batteries Power-fail detection occurs in the range of 4.75V to 4.5V with the tolerance Pin 3 grounded. If Pin 3 in connected to Vcco, then power-fail detection occurs in the range of 4.5 volts to 4.25 volts. By combining the DS1211 nonvolatile controller/decoder chip and lithium batteries, nonvolatile RAM operation can be achieved for up to eight CMOS memories. * Controller circuitry with monitoring and logic functions to make CMOS RAM nonvolatile * Controls up to 8 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 * Thermal operating ranges: * DS1211: 0°C to +70°C * DS1211-IND: -40° to +85°C * Voltage/tolerances: 5V ±5% or ±10%