Fully programmable linear feedback shift register
AssigneeGrumman Aerospace Corporation
InventorsDavid A. Giangano, Cecelia Jankowski
Life of this patent
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Abstract
Basic block shift registers are cascaded to form a fully programmable linear feedback shift register. Each of the basic block shift registers comprises a plurality of flip-flops, each of which includes control logic circuits. A polynomial equation is first fed into the linear feedback shift register for setting the respective flip-flops into predetermined logic states, which are used to encode messages to be shifted by the programmable linear feedback shift register. The number of flip-flops in the programmable linear feedback shift register can be varied, in accordance to the polynomial equation. Likewise, the polynomial equation also determines the number of times the programmable linear feedback shift register is to circulate the encoded messages.
Claims13
A fully programmable linear feedback shift register, comprising:
- a plurality of cascaded flip-flops;
- first means working cooperatively with the flip-flops for selecting a number of the flip-flops;
- second means connected to the outputs of the flip-flops and the first means for receiving data from the last of the selected flip-flops;
- first input means electrically connected to the flip-flops and a load control means for, upon a first command from the load control means, feeding a first set of data in parallel to the selected flip-flops, thereby establishing in the selected flip-flops a set of predetermined data, wherein the load control means, when not commanding the input means to feed the first set of data in parallel to the flip-flops, initiates a second command for inputting from a second input means a second set of data serially to the selected flip-flops;
- third means connected to the second means and working cooperatively with the load control means and the first input means for routing the data from the last of the selected flip-flops to the first of the selected flip-flops, thereby causing the data in the respective selected flip-flops to advance to succeeding selected flip-flops;
- whereby the second set of data is encoded by the set of predetermined data and wherein the encoded data are circulated through the selected flip-flops.
Apparatus for generating and decoding digital data, the apparatus having a plurality of shift registers in cascade, the shift registers being variable in length, each of the shift registers comprising:
- a plurality of cascaded flip-flops;
- a plurality of data lines, corresponding to the number of flip-flops, each electrically connected to a particular flip-flop;
- a plurality of enable lines each connected to a corresponding one of the flip-flops, a high logic state in an enable line signifying the selection of the corresponding flip-flop as a stage of the shift register;
- a load control means working cooperatively with the data lines and the selected flip-flops for initiating the feeding in parallel of a set of predetermined data from the data lines to the selected flip-flops, thereby establishing in the selected flip-flops predetermined data;
- the load control means, when not working cooperatively with the data lines for feeding in parallel a set of predetermined data to the flip-flops, initiates the inputting of a set of data serially to the selected flip-flops from a serial data input, the set of serial data being encoded by the set of previously stored predetermined data;
- a plurality of identical logic circuits each electrically connected to an output of a corresponding flip-flop, one of the logic circuits receiving data from the last of the selected flip-flops, the logic circuits having one common output;
- a feedback circuit having an input connected to the output of the logic circuits and an output electrically connected to the inputs of the respective flip-flops, the feedback circuit working cooperatively with the data lines for routing the data from the last of the selected flip-flops to the first of the selected flip-flops, thereby causing the data in the respective selected flip-flops to advance to succeeding flip-flops;
- whereby the set of encoded data is circulated through the selected flip-flops.
Dependencies are inferred from the claim text.