Electronic device and timer therefor with tamper event time stamp features and related methods

An electronic timer comprising:

• an oscillator and a crystal cooperating therewith to generate a clock reference signal;
• a real time clock (RTC) circuit for generating real time data based upon the clock reference signal, said RTC circuit comprising
• a plurality of registers for storing respective bits of the real time data, each register comprising a master latch for initially storing a real time data bit, a slave latch for subsequently storing the real time data bit, and a user latch for storing the real time data bit from said slave latch, and
• a controller for causing at least some of said registers to increment based upon the clock reference signal;
• a tamper circuit for receiving a tamper event signal and causing said user latches to hold current real time data bits based thereon until said tamper circuit is reset by a user;
• said user latches thus providing user accessible real time data when the tamper event signal does not indicate the tamper event has occurred, and providing a user accessible time stamp when the tamper event signal does indicate the tamper event has occurred;
• and
• a supply voltage detection circuit for prohibiting user access to said user latches when a supply voltage falls below a low supply threshold.

An electronic device comprising:

• a housing;
• a tamper sensor carried by said housing for detecting tampering with the electronic device and generating a tamper event signal based thereon;
• and
• an electronic timer connected to said tamper sensor and comprising
• a clock reference signal generator for generating a clock reference signal,
• a real time clock (RTC) circuit for generating real time data based upon the clock reference signal, said RTC circuit comprising a plurality of registers for storing respective bits of the real time data, each register comprising a master latch for initially storing a real time data bit, a slave latch for subsequently storing the real time data bit, and a user latch for storing the real time data bit from said slave latch, and a controller for causing at least some of said registers to increment based upon the clock reference signal, and
• a tamper circuit for receiving the tamper event signal from said tamper circuit and causing said user latches to hold current real time data bits based thereon until said tamper circuit is reset by a user;
• said user latches thus providing user accessible real time data when the tamper event signal does not indicate tampering has occurred, and providing a user accessible time stamp when the tamper event signal does indicate tampering has occurred.

A security method for determining the time of tampering with an electronic device, the method comprising:

• generating a clock reference signal;
• generating real time data based upon the clock reference signal by
• storing respective bits of the real time data in a plurality of registers, each register comprising a master latch for initially storing a real time data bit, a slave latch for subsequently storing the real time data bit, and a user latch for storing the real time data bit from the slave latch, and
• incrementing the registers based upon the clock reference signal;
• holding current real time data bits in the user latches based upon a tamper event signal indicating tampering with the electronic device;
• and
• resuming storing real time data in the user latches based upon the tamper event signal being reset.