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[/] [cic_core_2/] [trunk/] [rtl/] [verilog/] [cic_functions.vh] - Blame information for rev 5

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1 4 Juzujka 
/**
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 * Library: cic_functions
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 *
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 * library with functions for calculating parameters for CIC filter and Hogenauer pruning
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 */
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`ifndef _CIC_FUNCTIONS_VH_
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`define _CIC_FUNCTIONS_VH_
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`define M_PI 3.14159265359      // not all simulator defines PI
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/*********************************************************************************************/
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function reg unsigned [127 : 0] nchoosek;        ///< Binomial coefficient
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        input   integer n;
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        input   integer k;
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        reg unsigned [127:0] tmp;
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        integer i;
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        begin
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                tmp = 1.0;
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                for (i = 1; i <= (n - k); i = i + 1)
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                        tmp = tmp * (k + i) / i;
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                nchoosek = tmp;
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        end
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endfunction
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/*********************************************************************************************/
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function integer clog2_l;
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        input reg unsigned [127:0] depth;
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        reg unsigned [127:0] i;
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        begin
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                clog2_l = 0;
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                if (depth > 0) begin
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                        i = depth - 1;  // with "- 1" clog2(2^N) will be N, not N + 1
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                        for(clog2_l = 0; i > 0; clog2_l = clog2_l + 1)
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                                i = i >> 1;
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                end else
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                        clog2_l = -1;
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        end
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endfunction
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/*********************************************************************************************/
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function integer B_max_calc;
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        input integer N;
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        input integer R;
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        input integer M;
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        input integer INP_DW;
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        reg unsigned [127:0] RMpN;
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        begin
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                RMpN = (R * M) ** N;
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                B_max_calc = clog2_l(RMpN) + INP_DW - 1;
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        end
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endfunction
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/*********************************************************************************************/
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function integer B_out_calc;
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        input integer N;
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        input integer R;
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        input integer M;
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        input integer INP_DW;
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        input integer OUT_DW;
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        begin
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                B_out_calc = B_max_calc(N, R, M, OUT_DW) - B(2 * N, R, M, N, INP_DW, OUT_DW) + 1;
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        end
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endfunction
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/*********************************************************************************************/
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function integer flog2_l;
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        input reg unsigned [127:0] depth;
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        reg unsigned [127:0] i;
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        begin
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                i = depth;
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                for(flog2_l = 0; i > 1; flog2_l = flog2_l + 1)
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                        i = i >> 1;
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        end
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endfunction
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/*********************************************************************************************/
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function reg signed [127:0] h;
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        input   integer j;
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        input   integer k;
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        input   integer R;
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        input   integer M;
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        input   integer N;
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        integer c_stop;
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        integer i;
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        reg signed [127:0] tmp;
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        reg signed [127:0] prod_1;
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        reg signed [127:0] prod_2;
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        reg signed [127:0] summ;
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        begin
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                c_stop = k / (R * M);
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                if ((j >= 1)&&( j<=N )) begin
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                        tmp = 0;
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                        for (i = 0; i <= c_stop; i = i + 1) begin
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                                prod_1 = nchoosek(N, i);
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                                prod_2 = nchoosek(N - j + k - R * M * i, k - R * M * i);
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                                summ = prod_1 * prod_2;
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                                if (i % 2) summ = -summ;
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                                tmp = tmp + summ;
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                        end
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                end
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                else begin
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                        tmp = nchoosek(2 * N + 1 - j, k);
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                        if (k % 2) tmp = -tmp;
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                end
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                h = tmp;
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        end
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endfunction
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/*********************************************************************************************/
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function reg signed [127:0] F_sq;        ///< F()**2
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        input   integer j;
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        input   integer R;
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        input   integer M;
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        input   integer N;
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        integer c_stop;
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        reg signed [127:0] tmp;
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        integer i;
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        reg signed [127:0] h_jk;
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        begin
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                tmp = 0;
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                if (j <= N)
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                        c_stop = (((R * M -1 ) * N) + j - 1);
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                else
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                        c_stop = 2 * N + 1 - j;
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                for (i = 0;i <= c_stop; i = i + 1) begin
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                        h_jk = h(j, i, R, M, N);
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                        tmp = tmp + h_jk ** 2;
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                end
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                F_sq = tmp;
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        end
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endfunction
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/*********************************************************************************************/
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function integer B;
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        input   integer j;
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        input   integer R;
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        input   integer M;
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        input   integer N;
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        input   integer dw_in;
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        input   integer dw_out;
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        integer B_max;
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        reg signed [127:0] sigma_T_2Np1_sq;
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        reg signed [127:0] B_2Np1;
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        reg signed [127:0] B_exp_real;
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        integer B_out;
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        reg signed [127:0] F_sq_j;
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        reg signed [127:0] F_sq_2Np1;
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        begin
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                B_max = B_max_calc(N, R, M, dw_in);
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                if (j == 2 * N + 1) begin
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                        B = B_max - dw_out + 1;
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                end else begin
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                        B_2Np1 = B_max - dw_out + 1;
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                        F_sq_j = F_sq(j, R, M, N);
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                        F_sq_2Np1 = F_sq(2 * N + 1, R, M, N);
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                        sigma_T_2Np1_sq = (128'b1 << (2 * B_2Np1)) * F_sq_2Np1 / 12;
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                        B_exp_real = (sigma_T_2Np1_sq / F_sq_j * 6 / N);
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                        B_out = flog2_l(B_exp_real) / 2;
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                        B = B_out;
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                end
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        end
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endfunction
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/*********************************************************************************************/
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`endif
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