Self-tuning baud rate generator for UART applications
AssigneeTexas Instruments Incorporated
InventorRoshan J. Samuel
Life of this patent
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Abstract
The invention describes a baud rate generator for use in a sampled data system. This generator makes possible the sampling of asynchronous digital input data when its baud rate is not known, and does so without the use of phase-locked loop circuitry. The invention uses a digital counter to count the clock intervals between successive transitions in the digital input data. This process is repeated over a period of time sufficient to assure that recognizable recurring data patterns will occur in the data stream. The smallest interval recorded by the counter is captured and is directly related to the required sampling rate.
Claims10
A data processing apparatus for automatic baud rate detection of asynchronous data input comprising:
- an edge detector receiving asynchronous data input;
- an externally supplied sampling clock of many times higher frequency than expected baud rate;
- a master counter coupled to said sampling clock, said master counter counting between successive asynchronous data edges;
- a holding register coupled to sampling clock;
- a first comparator coupled to said sampling clock said first comparator acting to replace count in holding register with count in master counter if master count is less than holding count held in holding register, said replacement count fixed upon second detected edge;
- a sample counter coupled to sampling clock and further coupled to said edge detector, said sample counter driving a second comparator detecting a desired input sampling condition and driving a multiplexer with output coupled to data input of a data sampling register, said data sampling register also coupled to sampling clock and storing asynchronous data when sample counter value becomes equal to a predetermined fraction of holding count.
A data processing method of automatic baud rate detection comprising the steps of:
- detecting edges in asynchronous data;
- counting clock pulses of clock higher in frequency than the expected baud rate between consecutive detected edges;
- determining a minimum count between successive edges;
- and
- sampling asynchronous data on predetermined fraction of said minimum count.
Dependencies are inferred from the claim text.