A device takes as input an input bit stream and produces as output an output bit stream. A linear feedback shift register (LFSR) operates on the input bit stream and modifies the internal state of the LFSR if and only if a current bit value of the input bit stream differs from an immediately previous bit value of the input bit stream. A condenser having a compression factor N, operates on the input bit stream independently and asynchronously from the LFSR. The condenser produces a condensed value of the input bit stream. The condenser has a checksum register; a checksum accumulator register; and an adder for adding bits from the input bits stream to the checksum register. The low-order bit of the checksum register is shifted into the checksum accumulator register every N bits, and the condensed value produced by the condenser is the value in the checksum accumulator register. An exclusive-or mechanism combines the value of the LFSR and the condensed value produced by the condenser to produce the output bit stream.

A linear feedback shift register (LFSR) of interest is modelled in software by replicating the LFSR in at least two identically configured model LFSRs. One model LFSR contains only the higher order initial bits of the LFSR of interest, with zeroes in the lower order bit positions, and the other model LFSR has only the lower order bits, with zeroes in the higher order bit positions. The model LFSRs are represented by respective tables of model LFSR output values that would be produced after a predetermined number of register shifts. The tables are accessed based on the initial value of the LFSR of interest, and the results of one table are combined with the results of the other table using an exclusive OR operator to thereby determine the output of the LFSR of interest. The table lookup method results in increased speed vis-a-vis the performance of single-bit-per-cycle LFSRs, while the use of two logical model LFSRs with corresponding tables permits duplicative entries to be ignored when indexing the tables, thus greatly reducing the space required to store the tables.

A bitstream generator including a plurality of linear feed shift registers (LFSRs) operative to generate a bit stream and including: at least a first LFSR operative, when assigned as a generator during a first time period including at least one clock cycle, to provide an output bit in each clock cycle within the first time period, and at least a second LFSR operative, when assigned as an assignor during the first time period, to provide in each clock cycle an output bit for determining assignments of at least some of the plurality of LFSRs for a second time period following the first time period, the assignments including assignment as a generator, and assignment as an assignor, and a first combiner operative to combine output bits from all of the at least a first LFSR being assigned as generators thereby to produce during each clock cycle a single output bit which is provided to the bit stream. Related apparatus and methods are also provided.

An embodiment of the invention described in the specification and drawings is an apparatus and method of generating a phase-shifted maximum length pseudo-random noise (PN) sequence without resorting to complicated counters and clocking schemes. The apparatus includes a linear feedback shift register (LFSR) that has N stages and the ability to generate a first PN sequence at an output of its last stage. The LFSR is coupled to a first mask circuit and a second mask circuit for generating a second PN sequence and a third PN sequence. The apparatus further includes logic for selectively outputting bits from the second and third PN sequences to form a fourth PN sequence, which has a phase shift relative to the first PN sequence.

A system for receiving and processing digital video information such as a digital television broadcast, includes a modular platform which receives a plurality of hot pluggable cards. The platform is coupled by a high data rate graphics bus to a digital television display. The bus may provide encrypted information to prevent piracy of the video. Because the platform is modular in design, upgrades to the digital video system may be easily implemented using hot pluggable technology without changing the display. Thus, advances in electronics may be incorporated into the platform without necessitating that the owner replace the display.