![]() Refer to Pseudo Random Number Generation link for more robust LFSRs. Increasing the number of flipflops, and conditions in case statements shall result in wide range of output values. Kindly go through it.įrom the comment below, since there are three bits for flip flops, a maximum of eight states are possible, hence output can contain maximum of eight states (as e4 f2 da b6 60 66 3e). I have provided a testbench at EDAPlayground here, with the above mentioned changes. Like folows: parameter seed = 3'b000 // Arbitrary seed value I would prefer to use a parameter seed = 3'b000 which can easily be overridden while instantiation. Adding else condition can remove in unwanted latch creation.Īlso, initially, D<=3'b0 will have zero initial seed, and xoring operation shall also result in zero output ( D^D = 0^0 = 0), so the output shall never change. For example, consider two 3-bit XOR based LFSRs with different tap selections (Fig 2). The sequence of values generated by an LFSR is determined by its feedback function (XOR versus XNOR) and tap selection. In the always block, the condition if(rst) and else if(count.) can result into unintentional hardware. The data input to the LFSR is generated by XOR-ing or XNOR-ing the tap bits the remaining bits function as a standard shift register. After count reaches 20'd100000, it must be reset or re-initialized. Along with initializing D, count must be initialized. Verilog Code for a 16bit LFSR and explanations to get this on a FPGA development board: Part1. ![]() You have not initialized count variable here. Verilog FPGA Linear Feedback Shift Register - Tutorial.
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