| 摘要 |
Apparatus and methods for automatically determining the bit rate of an incoming signal are provided. The apparatus includes a counter (30), a logic circuit (20), and a histogram generating circuit (45 ). The counter (30) counts the number of fast reference clock cycles which fit within each pulse of the incoming signal far a statistically significant number of pulses and provides indications thereof to the logic circuit (20). The logic circuit (20) associates each of the indications with one of a plurality of allowable bit rates. The histogram generating circuit (45) tracks the number s of times the counts are associated with each allowable bit rate. In one embodiment, the allowable bit rate most often chosen is determined to be the bit race of the incoming signal. In another embodiment, if a DDS1 line rate is determined to be the bit rate mos t often chosen, the DDS2 rate associated with the DDS1 line rate is provisionally selected. Also, if a DDS2 line rate is determined to the bit rate most often chosen, the DDS2 line rate is provisionally selected.
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