cube.v

module cube_gen(CLK, reset, lock, init, busy, done,
                  Ax, Ay, Az, Bx, By, Bz);
   input CLK, reset, lock, init;
   wire  CLK, reset, lock, init;
   output       busy, done;
   reg          busy, done;
   output [15:0] Ax, Ay, Az, Bx, By, Bz;
   reg [15:0]    Ax, Ay, Az, Bx, By, Bz;

   reg [3:0]     state;
   reg [15:0]    d_step;
   reg [15:0]    cur_step;

   parameter     done_looping = 4'd0,
                   looping = 4'd1,
                   wait_for_init_low = 4'd2;

   reg [4:0]     counter;
   
   always @(posedge CLK) begin
      if (reset) begin
         cur_step <= 16'd0;

         Ax <= 16'd0;
         Ay <= 16'd0;
         Az <= 16'd0;
         Bx <= 16'd0;
         By <= 16'd0;
         Bz <= 16'd0;

         busy <= 1'b0;
         done <= 1'b0;

         state <= done_looping;
         $display("cube_gen being reset");
      end
      else if (lock) begin
         case (state)
           done_looping: begin
              if (init == 1'b1) begin
                 // not busy yet (no valid results out)
                 busy <= 1'b0;
                 // not done yet
                 done <= 1'b0;

                 counter <= 3'b0;
                 
                 state <= looping;
                 $display("cube_gen: done_looping with init high");
              end // if (init == 1'b1)
              else begin
                 $display("cube_gen: done_looping with init low");
                 busy <= 1'b0;
                 done <= 1'b0;
              end
           end
           looping: begin
              // not done yet.
              busy <= 1'b1;
              done <= 1'b0;
              if (counter == 0) begin
                 Ax <= 16'h4000;
                 Ay <= 16'h4000;
                 Az <= 16'h4000;
                 Bx <= 16'hc000;
                 By <= 16'h4000;
                 Bz <= 16'h4000;
              end
              else if (counter == 1) begin
                 Ax <= 16'h4000;
                 Ay <= 16'h4000;
                 Az <= 16'h4000;
                 Bx <= 16'h4000;
                 By <= 16'hc000;
                 Bz <= 16'h4000;
              end
              else if (counter == 2) begin
                 Ax <= 16'h4000;
                 Ay <= 16'h4000;
                 Az <= 16'h4000;
                 Bx <= 16'h4000;
                 By <= 16'h4000;
                 Bz <= 16'hc000;
              end
              else if (counter == 3) begin
                 Ax <= 16'hc000;
                 Ay <= 16'h4000;
                 Az <= 16'hc000;
                 Bx <= 16'h4000;
                 By <= 16'h4000;
                 Bz <= 16'hc000;
              end
              else if (counter == 4) begin
                 Ax <= 16'h4000;
                 Ay <= 16'hc000;
                 Az <= 16'hc000;
                 Bx <= 16'h4000;
                 By <= 16'h4000;
                 Bz <= 16'hc000;
              end
              else if (counter == 5) begin
                 Ax <= 16'hc000;
                 Ay <= 16'h4000;
                 Az <= 16'h4000;
                 Bx <= 16'hc000;
                 By <= 16'h4000;
                 Bz <= 16'hc000;
              end
              else if (counter == 6) begin
                 Ax <= 16'h4000;
                 Ay <= 16'hc000;
                 Az <= 16'h4000;
                 Bx <= 16'h4000;
                 By <= 16'hc000;
                 Bz <= 16'hc000;
              end
              else if (counter == 7) begin
                 Ax <= 16'h4000;
                 Ay <= 16'hc000;
                 Az <= 16'h4000;
                 Bx <= 16'hc000;
                 By <= 16'hc000;
                 Bz <= 16'h4000;
              end
              else if (counter == 8) begin
                 Ax <= 16'hc000;
                 Ay <= 16'hc000;
                 Az <= 16'h4000;
                 Bx <= 16'hc000;
                 By <= 16'hc000;
                 Bz <= 16'h4000;
              end
              else if (counter == 9) begin
                 Ax <= 16'hc000;
                 Ay <= 16'hc000;
                 Az <= 16'hc000;
                 Bx <= 16'hc000;
                 By <= 16'hc000;
                 Bz <= 16'h4000;
              end
              else if (counter == 10) begin
                 Ax <= 16'hc000;
                 Ay <= 16'hc000;
                 Az <= 16'hc000;
                 Bx <= 16'hc000;
                 By <= 16'h4000;
                 Bz <= 16'hc000;
              end
              else if (counter == 11) begin
                 Ax <= 16'hc000;
                 Ay <= 16'hc000;
                 Az <= 16'hc000;
                 Bx <= 16'h4000;
                 By <= 16'hc000;
                 Bz <= 16'hc000;
                 state <= wait_for_init_low;
              end

              counter <= counter + 1;
           end // case: looping
           wait_for_init_low: begin
              // now we're done
              busy <= 1'b0;
              done <= 1'b1;

              if (~init) begin
                 state <= done_looping;
              end
           end
         endcase // case (state)
      end
   end // always @ (posedge CLK)

endmodule // cube_gen