Quartus II - Verilog Flip Flop ModelSim Error

Question

I am writing a simple flipflop module in verilog and I am trying to write a top level module in instantiate my flipflop module and simulate it in ModelSim.

Here is my code below,

module flipflop(clck,D,Q);
  input  clck,D;
  output Q;

  wire R,S,S_g,R_g,Qa,Qb;

  assign R = ~D;
  assign S = D;

  nand(S_g,S,clck);
  nand(R_g,R,clck);
  nand(Qa,S_g,Qb);
  nand(Qb,R_g,Qa);

  assign Q = Qa;
endmodule

module TopLevel();
  reg  clck;
  reg  Q;
  wire D;

  flipflop p1(clck,D,Q);

  always begin
    #5 clck <=1;
    #5 clck <=0;
  end
endmodule

When I compile this code it runs fine, but when I try to simulate it, I get the following error:

# ** Error: (vsim-3053) C:/altera/13.1/FlipFlopsProjects/flipflop.v(30): Illegal output or inout port connection for "port 'Q'".

Any ideas or thoughts?

Answer 1

In top module, Q needed to be regs and D needed to be wires.

Answer 2

Error was in the declaration of inputs for the top level module...they needed to be wires, not regs