Real time clock using computer and separate counting means

Claim 1

A real time clock circuit for use with an electronic computing apparatus having a central processing unit (CPU) and a memory storage means including a real time clock register comprising: (a) means for generating first frequency clock signals; (b) means for feeding said first frequency clock signals into said CPU for counting in said real time clock register of said memory storage means; (c) first power supply means connected for providing power to said CPU for operating same; (d) means for generating second frequency clock signals; (e) means for counting said second frequency clock signals; (f) second power supply means, independent of said first power supply means, connected to said second frequency counting means for powering same, whereby said second frequency counting means counts said second frequency clock signals independently of said first power supply means; (g) means for disconnecting said first power supply means from said CPU; (h) means for reconnecting said first power supply means to said CPU after a time interval; (i) said second frequency counting means counting said second frequency clock signals during said time interval; (j) means for inhibiting counting of said second frequency counting means while said real time clock register is counting said first frequency clock signals; (k) means for incrementing said real time clock register in proportion to the counts accumulated in said second frequency counting means during said time interval, whereby said real time clock register is updated to account for first frequency clock signals not counted during said time interval.