David's Online LFSR Unroller

This web page computes the equations for an N-clock lookahead for the next state of and LFSR and generates the verilog code for the equations. You provide the length, the taps and the amount of lookahead. It defaults to a 32 bit LFSR with a maximal length tap setting and 8 clocks of lookahead. For lengths between 4 and 32, it will tell you whether or not your taps lead to a maximal length LFSR.

// Equations for 32 bit 8 clock LFSR lookahead.

// Feedback Taps 0x80200003. which yields a maximal length LFSR

// Search iterations = 26

x[0]  <= x[0] ^ x[14] ^ x[16] ^ x[18] ^ x[20] ^ x[24] ^ x[26] ^ x[28] ^ x[30];

x[1]  <= x[1] ^ x[15] ^ x[17] ^ x[19] ^ x[21] ^ x[25] ^ x[27] ^ x[29] ^ x[31];

x[2]  <= x[0] ^ x[16] ^ x[18] ^ x[20] ^ x[26] ^ x[28] ^ x[30];

x[3]  <= x[1] ^ x[17] ^ x[19] ^ x[21] ^ x[27] ^ x[29] ^ x[31];

x[4]  <= x[0] ^ x[18] ^ x[20] ^ x[28] ^ x[30];

x[5]  <= x[1] ^ x[19] ^ x[21] ^ x[29] ^ x[31];

x[6]  <= x[0] ^ x[20] ^ x[30];

x[7]  <= x[1] ^ x[21] ^ x[31];

x[8]  <= x[0];

x[9]  <= x[1];

x[10] <= x[2];

x[11] <= x[3];

x[12] <= x[4];

x[13] <= x[5];

x[14] <= x[6];

x[15] <= x[7];

x[16] <= x[8];

x[17] <= x[9];

x[18] <= x[10];

x[19] <= x[11];

x[20] <= x[12];

x[21] <= x[13];

x[22] <= x[14];

x[23] <= x[15];

x[24] <= x[16];

x[25] <= x[17];

x[26] <= x[18];

x[27] <= x[19];

x[28] <= x[20];

x[29] <= x[21];

x[30] <= x[22];

x[31] <= x[23];

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