Subversion Repositories random_pulse_generator

///////////////////////////////////////////////////////////////////////////////////////////////////

//

// File: random_pulse_generator.v

// File history:

//      Version 1: 2015-03-24: Created

//

// Description: 

//

// Poisson process generator. 

// Generate Poisson process with desired inversed rate (number of clocks per hit).

// The rate is defined by parameter LN2_PERIOD. For example, the LN2_PERIOD=4 will generate 

// in average one pulse per 16 clocks.

// 

// Author: Andrey Sukhanov

//

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`timescale 1ns/1ps

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module pseudo_random(input  clk, ce, rst, output reg [31:0] q);

// 32-bit uniform pseudo-random number generator, based on fibonacci LFSR

// Other 32-bit uniform random generators can be used as well.

wire feedback = q[31]^q[29]^q[28]^ q[27]^ q[23]^q[20]^ q[19]^q[17]^ q[15]^q[14]^q[12]^ q[11]^q[9]^ q[4]^ q[3]^q[2];

//feedback term B89ADA1C, other terms can be found from this table

// http://www.ece.cmu.edu/~koopman/lfsr/index.html

always @(posedge clk or posedge rst)

  if (rst)

    q <= 32'haaaaaaaa;   // the start is more random with this initialization

  else if (ce)

    q <= {q[30:0], feedback} ;

endmodule

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//''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

module random_pulse_generator( input clk, ce, rst, output reg q);

parameter LN2_PERIOD = 4; // 1 < LN2_PERIOD < 31

// log2 of the inversed process rate , 

parameter MASK = {LN2_PERIOD{1'b0}}; // any number with LN2_PERIOD bits can be used as a MASK

wire [31:0] uniform_random;

wire [LN2_PERIOD-1:0] sample;

pseudo_random pseudo_random_gen(clk, ce, rst, uniform_random);

assign sample = uniform_random[LN2_PERIOD-1:0]; // any subset of LN2_PERIOD bits can be used as a sample

always @ (posedge clk)

    if(ce) begin

        if (sample == MASK) q <= 1'b1;

        if (q) q <= 1'b0;

    end

endmodule

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