Time of day clock

Claim 1

A firmware/hardware time-of-day clock system for deriving a fundamental interval of time from a clock signal of an inherent frequency emanating from an untrimmed crystal oscillator, said fundamental interval of time being used to provide regulated seconds, minutes, hours and months time intervals, said system comprising: (a) means for continuous counting of the clock cycles of the inherent frequency clock signal from the crystal oscillator; (b) means for repeatedly indicating when a chosen number of clock cycles of the inherent frequency clock signal has been counted by said clock cycle counting means, said indicating means including means permitting modifying said chosen number of clock cycles to be counted by said clock cycle counting means; (c) means for generating an interrupt signal each time said chosen number of clock cycles have been counted; (d) means for counting a predetermined number of interrupt signals generated by said interrupt signal generating means; (e) first incrementing means for incrementing a 60-second counter upon said counting of said predetermined number of interrupt signals by said interrupt signal counting means; said first incrementing means including (1) means for resetting said interrupt signal counting means upon incrementing said 60-second counter; and (2) means for adding a predetermined correcting number to said chosen number of clock cycles indicating means for modifying said chosen number of clock cycles of the remaining inherent frequency clock signal to be counted to a value equal to the chosen number plus the correcting number so as to establish a fundamental interval of time.