module fir2 (clk, reset, sample, result);
input clk, reset;
input [7:0] sample;
output [9:0] result;
reg [9:0] result;
reg [7:0] samp_latch;
reg [16:0] pro;
reg [18:0] acc;
reg [19:0] clk_cnt;
reg [7:0] shift_0,shift_1,shift_2,shift_3,shift_4,shift_5,shift_6,shift_7,shift_8,shift_9,shift_10,shift_11,shift_12,shift_13,shift_14,shift_15,shift_16;
parameter coefs_0=9'b111111001,coefs_1=9'b111111011,coefs_2=9'b000001101,
coefs_3=9'b000010000,coefs_4=9'b111101101,coefs_5=9'b111010110,
coefs_6=9'b000010111,coefs_7=9'b010011010,coefs_8=9'b011011110,
coefs_9=9'b010011010,coefs_10=9'b000010111,coefs_11=9'b111010110,
coefs_12=9'b111101101,coefs_13=9'b000010000,coefs_14=9'b000001101,
coefs_15=9'b111111011,coefs_16=9'b111111001;
/*****************FUNCTION TO DO TWO'S COMPLEMENT MULTIPLICATION***************/
function [16:0] mul_tc;
/* this is needed for twos complement multiplication
*/
input [7:0] A;
input [8:0] B;
reg sgn;
begin
sgn = A[7] ^ B[8];
if (A[7] == 1'b1) A = ~A + 1'b1;
if (B[8] == 1'b1) B = ~B + 1'b1;
mul_tc = A * B;
if (sgn == 1'b1) mul_tc = ~mul_tc + 1'b1;
end
endfunction
/**************************************************************************/
/****************counter to count 18 clock cycles**********************/
always @ (posedge clk)
begin
if(reset)
clk_cnt<={18'b00_0000_0000_0000_0000,1'b1};
else
clk_cnt<={clk_cnt[18:0],clk_cnt[19]};
end
/***********************************************************************/
/****************start of the fir filter operation*********************/
always @(posedge clk)
begin
if (reset) begin
shift_0<=8'h00;
shift_1<=8'h00;shift_2<=8'h00;shift_3<=8'h00;shift_4<=8'h00;shift_5<=8'h00;
shift_6<=8'h00;shift_7<=8'h00;shift_8<=8'h00;shift_9<=8'h00;shift_10<=8'h00;
shift_11<=8'h00;shift_12<=8'h00;shift_13<=8'h00;shift_14<=8'h00;shift_15<=8'h00;
shift_16<=8'h00;
samp_latch<=8'h00;
acc<=18'o000000;
pro<=17'h00000;
end
else begin
if(clk_cnt[0]) begin
samp_latch<= sample;
acc<=18'h0_0000;
end
else if(clk_cnt[1])
pro <= samp_latch*coefs_0;
else if (clk_cnt[2])
begin
//pro<= mul_tc(shift_15,coefs_16);
pro<=shift_15*coefs_16;
acc<={ pro[16], pro[16], pro };
shift_16<=shift_15;
end
else if (clk_cnt[3])
begin
//pro<= mul_tc(shift_14,coefs_15);
pro<=shift_14*coefs_15;
acc<=acc+{ pro[16], pro[16], pro };
shift_15<=shift_14;
end
else if (clk_cnt[4])
begin
//pro<= mul_tc(shift_13,coefs_14);
pro<=shift_13*coefs_14;
acc<=acc+{ pro[16], pro[16], pro };
shift_14<=shift_13;
end
else if (clk_cnt[5])
begin
//pro<= mul_tc(shift_12,coefs_13);
pro<=shift_12*coefs_13;
acc<=acc+{ pro[16], pro[16], pro };
shift_13<=shift_12;
end
else if (clk_cnt[6])
begin
//pro<= mul_tc(shift_11,coefs_12);
pro<=shift_11*coefs_12;
acc<=acc+{ pro[16], pro[16], pro };
shift_12<=shift_11;
end
else if (clk_cnt[7])
begin
//pro<= mul_tc(shift_10,coefs_11);
pro<=shift_10*coefs_11;
acc<=acc+{ pro[16], pro[16], pro };
shift_11<=shift_10;
end
else if (clk_cnt[8])
begin
//pro<= mul_tc(shift_9,coefs_10);
pro<=shift_9*coefs_10;
acc<=acc+{ pro[16], pro[16], pro };
shift_10<=shift_9;
end
else if (clk_cnt[9])
begin
//pro<= mul_tc(shift_8,coefs_9);
pro<=shift_8*coefs_9;
acc<=acc+{ pro[16], pro[16], pro };
shift_9<=shift_8;
end
else if (clk_cnt[10])
begin
//pro<= mul_tc(shift_7,coefs_8);
pro<=shift_7*coefs_8;
acc<=acc+{ pro[16], pro[16], pro };
shift_8<=shift_7;
end
else if (clk_cnt[11])
begin
//pro<= mul_tc(shift_6,coefs_7);
pro<=shift_6*coefs_7;
acc<=acc+{ pro[16], pro[16], pro };
shift_7<=shift_6;
end
else if (clk_cnt[12])
begin
//pro<= mul_tc(shift_5,coefs_6);
pro<=shift_5*coefs_6;
acc<=acc+{ pro[16], pro[16], pro };
shift_6<=shift_5;
end
else if (clk_cnt[13])
begin
//pro<= mul_tc(shift_4,coefs_5);
pro<=shift_4*coefs_5;
acc<=acc+{ pro[16], pro[16], pro };
shift_5<=shift_4;
end
else if (clk_cnt[14])
begin
//pro<= mul_tc(shift_3,coefs_4);
pro<=shift_3*coefs_4;
acc<=acc+{ pro[16], pro[16], pro };
shift_4<=shift_3;
end
else if (clk_cnt[15])
begin
//pro<= mul_tc(shift_2,coefs_3);
pro<=shift_2*coefs_3;
acc<=acc+{ pro[16], pro[16], pro };
shift_3<=shift_2;
end
else if (clk_cnt[16])
begin
//pro<= mul_tc(shift_1,coefs_2);
pro<=shift_1*coefs_2;
acc<=acc+{ pro[16], pro[16], pro };
shift_2<=shift_1;
end
else if (clk_cnt[17])
begin
//pro<= mul_tc(shift_0,coefs_1);
pro<=shift_0*coefs_1;
acc<=acc+{ pro[16], pro[16], pro };
shift_1<=shift_0;
shift_0<=samp_latch;
end
else if (clk_cnt[18])
begin
acc<=acc+{pro[16],pro[16],pro};
end
else
begin
shift_0<=shift_0;
shift_1<=shift_1;
shift_2<=shift_2;
shift_3<=shift_3;
shift_4<=shift_4;
shift_5<=shift_5;
shift_6<=shift_6;
shift_7<=shift_7;
shift_8<=shift_8;
shift_9<=shift_9;
shift_10<=shift_10;
shift_11<=shift_11;
shift_12<=shift_12;
shift_13<=shift_13;
shift_14<=shift_14;
shift_15<=shift_15;
shift_16<=shift_16;
samp_latch<=samp_latch;
acc<=acc;
pro<=pro;
end
end
end
always @ (posedge clk)
begin
if (reset)
result<=10'h000;
else begin
if(clk_cnt[19])
result<=acc[18:9];
else
result<=result;
end
end
endmodule