RTC circuit with time value adjustment

• US 7,973,607 B1
• Filed: 04/22/2008
• Issued: 07/05/2011
• Est. Priority Date: 04/23/2007
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Ciaffi, Marco, Wilder, Daniel
• Primary Examiner(s): KINKEAD, ARNOLD M
• Application Number:
  US12/107,326
• Time in Patent Office: 1,169 Days
• Field of Search: 331/16, 331/34, 713/178, 713/601, 713/400, 340/10.2, 340/10.5
• US Class Current: 331/16
• CPC Class Codes: G06F 21/725 operating on a secure reference time value

Abstract

A technique involves the use of an electronic device having a real-time clock (RTC) circuit. In particular, the technique involves obtaining an RTC value from the RTC circuit. The RTC value is based on a previous time value and being arranged to represent current time. The technique further involves generating an adjustment factor arranged to adjust for imperfection in an oscillator of the RTC circuit, and providing a new time value based on the RTC value and the adjustment factor. The new time value represents current time at least as accurately as the RTC value.

Claims

1. In an electronic device having a real-time clock (RTC) circuit, a method comprising:

obtaining an RTC value from the RTC circuit, the RTC value being based on a previous time value and being arranged to represent current time;

generating an adjustment factor arranged to adjust for imperfection in an oscillator of the RTC circuit;

providing a new time value based on the RTC value and the adjustment factor, the new time value representing current time at least as accurately as the RTC value; and

supplying a user passcode based on the new time value, the user passcode being arranged to authenticate a user of the electronic device.

2. A method as in claim 1 wherein supplying the user passcode includes:

deriving a passcode seed based on the new time value;

creating, as the user passcode, a one-time passcode based on the passcode seed; and

outputting the one-time passcode on a display of the electronic device.

3. A method as in claim 1, further comprising:

prior to obtaining, generating, and providing, receiving an event signal indicating an occurrence of an event;

wherein the RTC value is obtained from the RTC circuit in response to receipt of the event signal;

wherein the adjustment factor is generated in response to the event signal; and

wherein the new time value is provided in response to the event signal.

4. A method as in claim 3 wherein receiving the event signal includes:

acquiring the event signal in response to actuation of a button circuit by a user.

12. A method as in claim 1 wherein the RTC circuit is external to a microprocessor of the electronic device, the microprocessor being arranged to obtain the RTC value from the RTC circuit, generate the adjustment factor, and provide the new time value.

13. A method as in claim 1 wherein the RTC circuit is internal to a microprocessor of the electronic device.

18. A method as in claim 1 wherein the electronic device is constructed and arranged to operate in an active mode during a first time period and a sleep mode during a second time period which is different than the first time period;

and

wherein obtaining an RTC value from the RTC circuit includes receiving a value which is based an oscillator frequency of the oscillator of the RTC circuit, the oscillator frequency being substantially the same regardless of whether the electronic device is operating in the active mode during the first time period or whether the electronic device is operating in the sleep mode during the second time period.

5. In an electronic device having a real-time clock (RTC) circuit, a method comprising:

obtaining an RTC value from the RTC circuit, the RTC value being based on a previous time value and being arranged to represent current time;

generating an adjustment factor arranged to adjust for imperfection in an oscillator of the RTC circuit;

providing a new time value based on the RTC value and the adjustment factor, the new time value representing current time at least as accurately as the RTC value; and

prior to obtaining, generating, and providing, receiving an event signal indicating an occurrence of an event;

wherein the RTC value is obtained from the RTC circuit in response to receipt of the event signal;

wherein the adjustment factor is generated in response to the event signal;

wherein the new time value is provided in response to the event signal; and

wherein receiving the event signal includes acquiring the event signal in response to a wake-up operation performed by the RTC circuit.

6. In an electronic device having a real-time clock (RTC) circuit, a method comprising:

obtaining an RTC value from the RTC circuit, the RTC value being based on a previous time value and being arranged to represent current time;

generating an adjustment factor arranged to adjust for imperfection in an oscillator of the RTC circuit;

providing a new time value based on the RTC value and the adjustment factor, the new time value representing current time at least as accurately as the RTC value;

wherein a memory of the electronic device stores a predetermined correction interval; and

wherein generating the adjustment factor includes;

indicating, as the adjustment factor, a number of times the predetermined correction interval stored in the memory spans a range between the previous time value and the RTC value.

7. A method as in claim 6 wherein the predetermined correction interval represents a number of minutes before any RTC value from the RTC circuit is behind current time by substantially a predetermined amount of time due to imperfection in the oscillator of the RTC circuit;

and wherein providing the new time value based on the RTC value and the adjustment factor includes;

providing, as the new time value, a result of the RTC value increased by one second for each time the predetermined correction interval spanned the range between the previous time value and the RTC value.

8. A method as in claim 6 wherein the predetermined correction interval represents a number of minutes before any RTC value from the RTC circuit is ahead of current time by substantially a predetermined amount of time due to imperfection in the oscillator of the RTC circuit;

and wherein providing the new time value based on the RTC value and the adjustment factor includes;

providing, as the new time value, a result of the RTC value decreased by one second for each time the predetermined correction interval spanned the range between the previous time value and the RTC value.

9. A method as in claim 6, further comprising:

outputting a frequency of the oscillator of the RTC circuit to a calibration circuit; and

loading the predetermined correction interval from the calibration circuit into the memory for use in generating the adjustment factor.

10. A method as in claim 9 wherein the calibration circuit is external to the electronic device.

11. A method as in claim 9 wherein the calibration circuit is internal to the electronic device.

14. An electronic circuit, comprising:

a real-time clock (RTC) interface constructed and arranged to couple to an RTC circuit; and

processing circuitry coupled to the RTC interface, the processing circuitry being constructed and arranged to;

obtain an RTC value from the RTC circuit through the RTC interface, the RTC value being based on a previous time value and being arranged to represent current time,

generate an adjustment factor arranged to adjust for imperfection in an oscillator of the RTC circuit,

provide a new time value based on the RTC value and the adjustment factor, the new time value representing current time at least as accurately as the RTC value, and

supply a user passcode based on the new time value, the user passcode being arranged to authenticate a user.

15. An electronic circuit as in claim 14, further comprising:

a display coupled to the processing circuitry;

wherein the processing circuitry, when supplying the user passcode, is constructed and arranged to (i) derive a passcode seed based on the new time value, (ii) create, as the user passcode, a one-time passcode based on the passcode seed, and (iii) output the one-time passcode on the display to the user.

19. An electronic circuit as in claim 14 wherein the electronic circuit is constructed and arranged to operate in an active mode during a first time period and a sleep mode during a second time period which is different than the first time period;

and

wherein a frequency of the oscillator of the RTC circuit is substantially the same regardless of whether the electronic circuit is operating in the active mode during the first time period or whether the electronic circuit is operating in the sleep mode during the second time period.

16. An electronic circuit, comprising:

a real-time clock (RTC) interface constructed and arranged to couple to an RTC circuit;

processing circuitry coupled to the RTC interface, the processing circuitry being constructed and arranged to;

obtain an RTC value from the RTC circuit through the RTC interface, the RTC value being based on a previous time value and being arranged to represent current time,

generate an adjustment factor arranged to adjust for imperfection in an oscillator of the RTC circuit, and

provide a new time value based on the RTC value and the adjustment factor, the new time value representing current time at least as accurately as the RTC value; and

a memory which stores a predetermined correction interval;

wherein the processing circuitry, when generating the adjustment factor is constructed and arranged to indicate, as the adjustment factor, a number of times the predetermined correction interval stored in the memory spans a range between the previous time value and the RTC value.

17. An electronic circuit as in claim 16 wherein a calibration circuit is constructed and arranged to acquire a frequency of the oscillator of the RTC circuit;

and wherein the processing circuitry is further constructed and arranged to;

load the predetermined correction interval from the calibration circuit into the memory for use in generating the adjustment factor.

20. An electronic circuit as in claim 16 wherein the electronic circuit is constructed and arranged to operate in an active mode during a first time period and a sleep mode during a second time period which is different than the first time period;

and

wherein a frequency of the oscillator of the RTC circuit is substantially the same regardless of whether the electronic circuit is operating in the active mode during the first time period or whether the electronic circuit is operating in the sleep mode during the second time period.