Oscillator frequency adjustment
AssigneeRenesas Electronics Corporation
InventorsVolker Langer, Thomas Kattwinkel
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Abstract
Oscillator circuitry is disclosed. The oscillator circuitry comprises a free-running oscillator for generating pulses at a frequency, and a frequency adjustment circuit for adaptively adjusting the frequency of the free-running oscillator. The frequency adjustment circuit comprises a counter configured to count a number of pulses generated by the free-running oscillator and logic configured to compare the number of pulses with an expected number of pulses (corresponding to a target frequency) to determine a difference value and to adjust the frequency of the free-running oscillator in dependence on the difference value. The frequency adjustment circuit is configured, in response to receiving a synchronisation pulse, to trigger an update of the number of pulses to be compared.
Claims30
Oscillator circuitry comprising:
- a free-running oscillator for generating pulses at a frequency;
- and
- a frequency adjustment circuit for adaptively adjusting the frequency of the free-running oscillator, the frequency adjustment circuit comprising:
- a counter configured to count a number of pulses generated by the free-running oscillator;
- and
- logic configured to:
- compare the number of pulses with an expected number of pulses to determine a difference value;
- determine whether a magnitude of the difference value exceeds a pre-defined threshold value, wherein the pre-defined threshold value is non-zero;
- upon determination that the magnitude of the difference value does not exceed the pre-defined threshold value, adjust the frequency of the free-running oscillator in dependence on the difference value;
- and
- upon determination that the magnitude of the difference value exceeds the pre-defined threshold value, to adjust the frequency of the free-running oscillator in dependence on another pre-defined value,
- wherein the frequency adjustment circuit is configured, in response to receiving a synchronisation pulse, to trigger an update of the number of pulses to be compared.
A method of adjusting a free-running oscillator generating pulses at a frequency, the method comprising:
- counting a number of pulses generated by the free-running oscillator;
- comparing the number of pulses with an expected number of pulses to determine a difference value;
- determining whether a magnitude of the difference value exceeds a pre-defined threshold value, wherein the pre-defined threshold value is non-zero;
- adjusting the frequency of the free-running oscillator in dependence upon:
- the difference value when the magnitude of the difference value does not exceed the pre-defined threshold value;
- or
- another predefined value when the magnitude of the difference value exceeds the pre-defined threshold value;
- in response to receiving a synchronisation pulse, triggering an update of the number of pulses to be compared.
Dependencies are inferred from the claim text.