Microprocessor programmable clock calibration system and method
AssigneeAnalog Devices, Inc.
InventorsShaun Bradley, Kieran Heffernan, Tomas Tansley, Yang Ling
Life of this patent
Estimating the term…
Abstract
A microprocessor programmable clock calibration device compares, in response to a calibration command from a programmable processor, turns on a normally off reference oscillator clock, compares the frequency of the reference oscillator clock with the frequency of a calibratable oscillator clock, turns off the reference oscillator clock and adjusts, in response to a difference in those frequencies, the frequency of the calibratable oscillator clock towards that of the reference oscillator clock.
Claims25
A microprocessor programmable clock calibration system comprising:
- a normally off reference oscillator clock;
- a normally on calibratable oscillator clock;
- a programmable processor for providing a calibration command which turns on said reference oscillator clock;
- a calibration control system responsive to said calibration command for comparing frequencies of said clocks, said processor turning off said reference oscillator clock after the frequencies are compared, wherein the calibration control system includes a first counter to count the reference oscillator clock and a second counter to count the calibratable oscillator clock and the frequencies of the clocks are compared by comparing the counts of the two counters;
- and
- a trim circuit responsive to a difference in said clock frequencies for adjusting said calibratable clock towards said reference clock, wherein the trim circuit is driven by the calibration control system and the calibration control system includes a state machine with states of idle, reset calibration logic, enable calibration, wait for counters to stop, compare oscillator clock frequencies and adjust calibratable oscillator clock frequency.
A microprocessor programmable clock calibration method comprising:
- in response to a calibration command, turning on a normally off reference oscillator clock, comparing frequency of the reference oscillator clock to frequency of a calibratable oscillator clock, turning off the reference oscillator clock, wherein a first counter is to count the reference oscillator clock and a second counter is to count the calibratable oscillator clock and the frequencies of the clocks are compared by comparing the counts of the two counters;
- and
- adjusting, in response to a difference in these frequencies, the frequency of the calibratable oscillator clock toward that of the reference oscillator clock by a trim circuit, wherein the trim circuit is driven by a calibration control system including a state machine with states of idle, reset calibration logic, enable calibration, wait for counters to stop, compare oscillator clock frequencies and adjust calibratable oscillator clock frequency.
A microprocessor programmable clock calibration system comprising:
- a normally off reference oscillator clock;
- a normally on calibratable oscillator clock;
- a programmable processor for providing a calibration command which turns on said reference oscillator clock;
- a calibration control system responsive to said calibration command for comparing frequencies of said clocks, said processor turning off said reference oscillator clock after the frequencies are compared, wherein the calibration control system includes a first counter to count the reference oscillator clock and a second counter to count the calibratable oscillator clock and the frequencies of the clocks are compared by comparing the counts of the two counters;
- and
- a trim circuit responsive to a difference in said clock frequencies for adjusting said calibratable clock towards said reference clock, wherein the trim circuit is driven by the calibration control system that includes a state machine with states of idle, wait for counters to stop and adjust calibratable oscillator clock frequency.
Dependencies are inferred from the claim text.