Real time clock content validation
View Patent ↗Disclosed is a method of validating the contents of a real-time clock in a digital circuit. A plurality of memory elements create a first random signature value when power is newly applied to a circuit. The plurality of memory elements maintain the first random signature value while power to the circuit is maintained. The first random signature value is stored as a reference value such that the reference value is not altered by a power interruption. When power to the circuit is lost and then regained, a second random signature value is created. The second random signature value likely will no longer match the reference value because both the reference value and the second signature are random. When the reference value does not match the signature value, the real-time clock value is considered invalid. User input may be employed to correct the real-time clock value.
1. A digital circuit for performing a method of validating the contents of a real-time clock, the method comprising:
applying power to a plurality of memory elements, wherein said plurality of memory elements have a random state when power is newly applied to said plurality of memory elements;
creating a random signature using said random state of said plurality of memory elements;
maintaining said random signature in said plurality of memory elements while power to said circuit is maintained;
storing said random signature as a reference value, wherein said reference value is not altered by a power interruption;
comparing said reference value to said random signature; and
identifying when said random signature does not match said reference value.
2. The method according to claim 1 , comprising the additional steps of:
employing user input to correct said real-time clock;
creating a second random signature value by providing power to said circuit
rewriting said reference value to be equal to said second random signature value.
3. The method according to claim 1 , wherein said random signature value is generated through flip-flops.