Modules

creation

module <name> #(PARAM) (port_list)
   ... code ...
endmodule

ports

module can have ports, they must be of one of the following type:

• input

• output

• inout

Note

ports are considered by default of type wire

ports type can be defined in the port list or inside the module, not both.

module test (
   input [3:0] a,
               b,
   output [7:0] data
);

wire [3:0] a, b;
reg  [7:0] data;

// ... code ...

endmodule

// OR

module test (
   input [3:0] a,
               b,
   output reg [7:0] data
);

// ... code ...

endmodule

ports connection

can be connected by order or by name.

What is more robust is by name and is the method we used. This avoids easy mistakes with port order. non connected ports have a high value impedance Z by default.

example

Example of a parametric module with ports. Moreover, it is instantiating a variable number of sub-module with a for loop

module debounce #(
      parameter DEBOUNCE_TIME = 5000,
      parameter N = 1
   )(
      output [N-1:0] o_switch,
      input  i_clk,
      input  i_reset,
      input  [N-1:0] i_switch 
   );

   genvar i;

   generate
      for (i = 0; i < N; i = i + 1) begin : DB
         debounce_core  #( .DEBOUNCE_TIME(DEBOUNCE_TIME) ) db_core(
            .o_switch (o_switch[i]),
            .i_clk(i_clk),
            .i_reset (i_reset),
            .i_switch(i_switch[i])
         );
      end
   endgenerate

endmodule