Real time clock and method for providing same
First Claim
1. A real time clock comprising:
- an oscillator developing an oscillator signal;
a digital counter having an oscillator input coupled to said oscillator signal, a counter adjustment input, and a real time counter register which provides a count value that can represent a current time;
a temperature measurement circuit operative to measure an ambient temperature and provide a digital temperature value; and
a digital processor operative to use said temperature value to provide a counter adjustment signal, said digital processor being further operative to read said real time counter register and providing said current time.
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Accused Products
Abstract
A real time clock includes an oscillator, a digital counter, a temperature sensor, and a digital processor. The digital processor can read the temperature measured by the temperature sensor and utilize this information to generate an adjustment value for the digital counter. The digital counter is coupled to the digital processor and has an adjustment stage which the digital processor writes into in order to compensate for any oscillator error due to temperature variation. The digital processor may also be coupled to memory storing a temperature adjustment look-up table for use in generating the adjustment value. A method of the present invention includes the initial steps of generating an adjustment look-up table and storing it in non-volatile memory. A method of the present invention further includes the ongoing steps of measuring an ambient temperature, generating an adjustment value, adjusting the digital counter to improve the accuracy of the real time clock, and storing a new alarm time for a future adjustment.
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Citations
30 Claims
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1. A real time clock comprising:
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an oscillator developing an oscillator signal; a digital counter having an oscillator input coupled to said oscillator signal, a counter adjustment input, and a real time counter register which provides a count value that can represent a current time; a temperature measurement circuit operative to measure an ambient temperature and provide a digital temperature value; and a digital processor operative to use said temperature value to provide a counter adjustment signal, said digital processor being further operative to read said real time counter register and providing said current time. - View Dependent Claims (2, 7, 8)
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3. A real time clock comprising:
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an oscillator developing an oscillator signal, said oscillator signal provided at a frequency less than 4 megahertz (MHz); a digital counter having only a single oscillator input coupled to said oscillator signal, a counter adjustment input, and a real time counter register which provides a count value that can represent a current time; a temperature measurement circuit operative to measure an ambient temperature and provide a digital temperature value; and a digital processor operative to use said temperature value to provide a counter adjustment signal, said digital processor being further operative to read said real time counter register and providing said current time. - View Dependent Claims (4, 5, 6)
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9. A real time clock comprising:
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an oscillator developing an oscillator signal; a digital counter having an oscillator input coupled to said oscillator signal, a counter adjustment input, a real time counter register which provides a count value that can represent a current time, an adjustment stage, a counter register stage and an alarm stage; a temperature measurement circuit operative to measure an ambient temperature and provide a digital temperature value; and a digital processor operative to use said temperature value to provide a counter adjustment signal, said digital processor being further operative to read said real time counter register and providing said current time. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A computer system with a real time clock comprising:
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a central processing unit (CPU); digital memory coupled to said CPU; an oscillator providing an oscillator signal; a digital counter having an oscillator input coupled to said oscillator signal, a counter adjustment input, and a real time counter register accessible by said CPU which provides a count value that can represent a current time; a temperature measurement circuit operative to measure an ambient temperature and provide a digital temperature value accessible by said CPU; and counter adjustment means implemented on said CPU for providing said counter adjustment signal to said digital counter in response to said digital temperature value. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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22. A computer system with a real time clock comprising:
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a central processing unit (CPU); digital memory coupled to said CPU, said digital memory including non-volatile memory and volatile memory; a temperature adjustment look-up table stored in said non-volatile memory; an oscillator providing an oscillator signal a single frequency; a digital counter having only a single oscillator input coupled to said oscillator signal, a counter adjustment input, and a real time counter register accessible by said CPU which provides a count value that can represent a current time, wherein said CPU, said digital memory, and said digital counter are coupled to a common bus; a temperature measurement circuit including a temperature transducer having a temperature variable analog signal and an analog-to-digital (A/D) converter coupled to said analog signal for providing said digital temperature value, wherein said temperature measurement circuit is operative to measure an ambient temperature and provide a digital temperature value accessible by said CPU; and counter adjustment means implemented on said CPU for providing said counter adjustment signal to said digital counter in response to said digital temperature value, wherein said counter adjustment means utilizes said look-up table to provide said counter adjustment signal. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30)
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Specification