Apparatus and method for short cycling sequences of a p-code generator

DETAILED DESCRIPTION A P-code generator of a Global Positioning System is provided comprising a plurality of pseudo-random number generators interconnected to generate a ranging P-code.
Each of such generators comprises an improved sequencer wherein short cycling of such sequencer is accomplished with less circuitry for generating an initial vector word upon reinitialization of the sequencer.
In accordance with the present invention a pseudo-random number generator is provided comprising shift register means including a plurality of stages and having a serial input, a serial output and shifting in accordance with an input signal, decoder means coupled to an output of each stage of the shift register means for generating a decode signal when the contents of the shift register equals a predetermined vector word, and means coupled to the decode signal and the outputs of a plurality of predetermined stages of the shift register means for generating a feedback signal coupled to the serial input of the shift register means to short cycle the pseudo-random number generator.
The shift register means is preloaded with an initial vector word.
The feedback signal generating means comprises an exclusive-OR gate.
In accordance with a further feature of the invention a P-code generator of a Global Positioning System is provided comprising a plurality of pseudo-random number generators for generating a ranging P-code, each of the generators having a sequencer means for determining the ranging P-code, shift register means included in each of the sequencer means comprising a plurality of stages, the shift register means having a serial input, a serial output, and shifting in accordance with an input signal, decoder means coupled to an output of each stage of the shift register means for generating a decode signal when the contents of the shift register means equals a predetermined vector word, and means coupled to the decode signal and the outputs of a plurality of predetermined stages of the shift register means for generating a feedback signal coupled to the serial input of the shift register means to short cycle the sequencer means