My code compiles now, but my outputs RG (z1) and RN (z0) are incorrect and show up as X's in the simulation. I have no idea how to implement double JKFFs using "always @" code. I think I need to somehow fix my jkff module so that I do not get X's in my code. The outputs for e and f for 0~30ns should be 00 00 11, but they show only X's.

![Simulation Result][1]


The JKFFs I should be implementing is:
![JKFFs][2]


    module main_file(
    input r,
    input x1,
    input x0,
	input clk,
    output RN,
    output RG
    );
    wire ss0, ss1, a1; 
    jkff i_jkff
    ( 
    .s0(ss0),  
    .s1(ss1)
    );	
    assign a1=(!ss0||x1);
    assign RN=(x0&&ss1&&a1);
	assign RG=(x1&&ss1&&!ss0);
    endmodule

Below is the jkff implementation:

    module jkff(
    input clk, r, x1, x0,
    output reg s0,
    output reg s1
    );
     wire a1, a2, a3, a4, J1, K1, J0, K0;
     assign a1=(x1||s0);
     assign J1=(a1&&x0);
     assign a2=(x1||!s0);
     assign K1=(x0&&a2);
     assign a3=(x1||x0);
     assign J0=(a3&&!s1);
     assign a4=(x1||s1);
     assign K0=(a4&&x0);
     
     always @(posedge clk or posedge r)
     begin
        if (r) begin
            s1<=0;
            end
        else begin
        case ({J1,K1})
        2'b00: s1<=s1;
        2'b01: s1<=1'b0;
        2'b10: s1<=1'b1;
        2'b11: s1<=~s1;
        endcase
    end
    end
    endmodule

Below is the test bench

    module main_file_tb(
    );

	reg a;
	reg b;
	reg c;
	reg d;
	wire e;
	wire f;

	main_file main_file
	(
	.r(a),
	.x1(b),
	.x0(c),
	.clk(d),
	.RN(e),
	.RG(f)
	);

	initial begin
	a=0;b=1;c=1;d=1;
	#10;
	a=0;b=0;c=1;d=1;
	#10;
	a=0;b=1;c=1;d=1;
	#10;
	a=1;b=0;c=0;d=0;
	#10;
	a=0;b=0;c=1;d=1;
	#10;
	a=0;b=0;c=1;d=1;
	#10;
	a=0;b=0;c=1;d=1;
	#10;
	a=0;b=0;c=1;d=1;
	#10;
	a=1;b=0;c=0;d=0;
	#10;
	a=0;b=1;c=1;d=1;
	#10;
	a=1;b=0;c=0;d=0;
	#10;
	end
	endmodule

  [1]: https://i.sstatic.net/L0k1h.png
  [2]: https://i.sstatic.net/HT6En.jpg