Low-power baud rate generator including two oscillators
AssigneeOki Electric Industry Co., Ltd.
InventorsSeiichi Yamazaki, Sumihiro Takashima
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Abstract
A baud rate generator has a first oscillator that generates a first clock signal, and a second oscillator that generates a second clock signal with higher frequency but lower frequency accuracy. The first oscillator employs an external resonator but the second does not. The baud rate generator uses the first clock signal to measure the frequency of the second clock signal, then determines a division ratio by which to divide the frequency of the second clock signal, then divides the second clock signal by this division ratio to generate a crock signal for use in serial communication.
Claims29
A method of generating a clock signal for serial communication from a first oscillator and a second oscillator, said first oscillator oscillating at a lower frequency than said second oscillator but with higher frequency accuracy, comprising the steps of:
- generating a first clock signal from said first oscillator;
- generating a second clock signal from said second oscillator;
- counting said first clock signal to determine an interval of time;
- counting said second clock signal during said interval of time to obtain a count value;
- dividing said count value by a certain integer to obtain a division ratio;
- and
- dividing said second clock signal in frequency by said division ratio, thereby generating said clock signal for serial communication.
A baud rate generator for generating a clock signal for serial communication, comprising:
- a first oscillator for generating a first clock signal;
- a second oscillator for generating a second clock signal;
- a first counter coupled to count said first clock signal, to thereby determine an interval of time, and output a gate signal that is active only during said interval;
- a second counter coupled to count said second clock signal while said gate signal is active, thereby generating a count value;
- a programmable frequency divider coupled to divide said second clock signal by a division ratio, thereby generating said clock signal for serial communication;
- and
- a processor unit coupled to read said count value from said second counter, divide said count value by a certain integer, thereby calculating said division ratio, and load said division ratio into said programmable frequency divider.
A baud rate generator for generating a clock signal for serial communication, comprising:
- a first oscillator for generating a first clock signal;
- a second oscillator for generating a second clock signal;
- a programmable counter coupled to count said second clock signal during a certain interval of time, thereby generating a count value, and to divide said second clock signal by a division ratio, thereby generating said clock signal for serial communication;
- and
- a processor unit coupled to count said first clock signal, thereby determining said interval of time, to read said count value from said programmable counter, to divide said count value by a certain integer, thereby calculating said division ratio, and to load said division ratio into said programmable counter.
Dependencies are inferred from the claim text.