Hybrid scrambled transmission coding
First Claim
1. A method of transmitting digital data sequences from a transmitting device to a receiving device across a serial channel, wherein the receiving device recovers the timing of the digital data sequences from the digital data sequence itself, the method comprising:
- scrambling multiple digital data sequences;
sequentially transmitting the scrambled digital data sequences across the serial channel;
transmitting unscrambled channel control character sequences, each sequence comprising at least twenty bits, across the channel between the scrambled digital data sequences; and
measuring DC imbalance in one of the scrambled digital data sequences and selecting and inserting into the scrambled digital data sequence an additional unscrambled control character that counters the measured DC imbalance.
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Accused Products
Abstract
In one embodiment, a hybrid backplane coding scheme transmits data using lengthy sequences of scrambled data, separated by 8b/10b control character sequences that prepare the receiver for the next scrambled sequence and permit realignment if necessary. Advantageously, the sender of the scrambled data can be changed during the control character sequence. The hybrid backplane coding scheme can be designed such that the power spectral density of scrambled data and control character sequences are similar, which permits good performance with high-speed electrical differential receivers. Other embodiments are described and claimed.
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Citations
28 Claims
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1. A method of transmitting digital data sequences from a transmitting device to a receiving device across a serial channel, wherein the receiving device recovers the timing of the digital data sequences from the digital data sequence itself, the method comprising:
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scrambling multiple digital data sequences; sequentially transmitting the scrambled digital data sequences across the serial channel; transmitting unscrambled channel control character sequences, each sequence comprising at least twenty bits, across the channel between the scrambled digital data sequences; and measuring DC imbalance in one of the scrambled digital data sequences and selecting and inserting into the scrambled digital data sequence an additional unscrambled control character that counters the measured DC imbalance. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A distributed packet switch comprising:
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an electrical backplane comprising a plurality of differential signal trace pairs and a plurality of line cards and at least one switch fabric card coupled to the electrical backplane, each line card coupled to the at least one switch fabric card by at least two of the differential signal trace pairs, each of the differential signal trace pairs used for unidirectional communication either from a line card to a switch fabric card or from a switch fabric card to a line card, the line cards and switch fabric cards communicate digital data sequences across the differential signal trace pairs in a series of epochs, each epoch on a differential signal trace pair that is communicating a corresponding digital data sequence during that epoch comprising an unscrambled channel control character sequence of at least twenty bits and a scrambled version of the corresponding digital data sequence; wherein the line cards comprise transmitters that measure DC imbalance in one of the scrambled digital data sequences and select and insert into the scrambled digital data sequence an additional unscrambled control character that counters the measured DC imbalance. - View Dependent Claims (23, 24, 25, 26, 27, 28)
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Specification