The DS1212 Nonvolatile Controller x16 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 4.5V to 4.25V. By combining the DS1212 nonvolatile controller/decoder chip with lithium batteries, nonvolatile RAM operation can be achieved for up to 16 CMOS memories.