Method and device for filtering glitch in asynchronous data communication interface
A data signal, asynchronous data technology, used in synchronous signal speed/phase control, redundancy in operation, data error detection, electrical digital data processing, etc.
Inactive Publication Date: 2008-04-09
TEXAS INSTR INC
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[0018] The numerous novel aspects of the invention will be elucidated with particular reference to the presently preferred exemplary embodiments. However, it should be understood that such embodiments provide only a few examples of the many advantages and innovations herein. For example, although the embodiments of the present invention described here relate to the ISO7816 standard data interface, it is also applicable to any asynchronous data interface. In general, statements made in the specification to this application do not necessarily define the boundaries of the invention, as set forth from different aspects in different appended claims on the invention. Furthermore, some statements may apply to some aspects of the invention but not to others.
[0019] figure 2 It is a timing chart for signals conforming to the ISO7816 standard, and the timing is displayed on the horizontal axis. The complete character is shown in the figure, starting at time 0 and ending at time tn....
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An apparatus and a method for filtering glitches in a data communications controller receiving asynchronous input data signals varying between two signal levels representing two bit values and having a predetermined input bit period, and sending output data signals corresponding to the input data signals. The glitches comprise reversals of signal level, having a glitch duration less than the predetermined bit period, on the input data signals. In a glitch detector (68), glitches are detected in the input data signals by detecting reversals of signal level having a predetermined duration less than the predetermined input bit period. A glitch time value corresponding to the glitch duration is determined, and then a sampling clock rate is determined from the glitch time value. In a glitch filter (44),The input data signals are sampled at the sampling clock rate to generate a sequence of input data samples. A predetermined voting number of input data samples are monitored by a voting unit (54) and an output signal is provided, representing the value of a majority of the sequential input data samples. Finally, a voting number of subsequent input data samples are monitored and output signals are provided, representing the value of a majority of those subsequent input data samples.
Description
technical field [0001] This invention relates to asynchronous data communication interface controllers, and more particularly to methods and apparatus for detecting and filtering glitches in asynchronous digital signals received by these controllers. Background technique [0002] In asynchronous transmission, data is encoded as a series of pulses, including start bits, and including stop bits or guard bands. The sending unit sends a start bit to inform the receiving unit that a character is about to be sent. The character is then sent, followed by a stop bit or guard band, indicating that the transmission of the character is complete. Schemas for asynchronous communication are typically defined in standards established by standard-setting bodies such as the American National Standards Institute (ANSI), the International Telecommunication Union (ITU), and the International Organization for Standardization (ISO). [0003] Asynchronous communications are commonly used to tran...
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IPC IPC(8): G06F11/10H04L25/38G06F11/00G06F11/14H04L7/04
CPCG06F11/002G06F11/14
Inventor 酒井毅R·拉维库马M·J·拉赫曼
Owner TEXAS INSTR INC