creating 16to4 bit priority encoder with 4to2 bit encoder

Question

I want to make a 16to4 bit priority encoder just using 4 to 2 priority encoder? I am using verilog code, I used six 4 to 2 encoder. at the first I'v used 4 encoders and after that I put their output the input of the other tow encoders; but it doesn't work correctly at all!

Answer 1

module pri16to4
   (input  wire[15:0] in,
    output wire       valid,
    output wire [3:0] out);

   wire[1:0] pe3, pe2, pe1, pe0;

   U3(in[15:12], pe3);
   U2(in[11:8],  pe2);
   U1(in[7:4],   pe1);
   U0(in[3:0],   pe0);

   assign valid = (in != 0);
   assign out = (in[15:12] != 0)? {2'b11, pe3} :
                (in[11:8]  != 0)? {2'b10, pe2} :
                (in[7:4]   != 0)? {2'b01, pe1} :
                (in[3:0]   != 0)? {2'b00, pe0} : 0;

endmodule

For future reference - if you've got a Verilog problem, show that you've done some work, and post the code that doesn't work. If you've got a homework problem, ask your prof.