What is the purpose of this module?

Question

module InoutConnect(
                .X1(internal), 
                .X2(internal)
                );


   parameter width = 1;

   inout [ width - 1 : 0 ] internal;
endmodule // InoutConnect

In the above code what is the format used, I know that while instantiating the module .x1 is use to match the variable name but what about module definition. What does it mean here?

Answer 1

it is called explicit port declaration, meaning that the external world will know this port by its explicit names, X1 and X2 in your case, though internally the same port will be known as internal in your case.

So, in your example you connect both ports to the same internal variable (looks bad to me :)) Though, this is one of the possible uses, in particular if you need to identical output ports. The other example is remapping internal structs or arrays to multiple potrts:

module m(
   output .arr1(array[2:0]),
   output .arr2(array[7:3]),
   input logic [7:0] input_array
)
   logic [7:0] array;
   ...
   always_ff @(posedge clk)
       array <= input_array;
   ...
endmodule

So, above you can use your array as the whole internally, but it will have a different representation in the external world.

See 23.2.2.2 ANSI style list of port declarations for more info.

Answer 2

The InoutConnect module is used to create an alias between two different signal names. For example

wire [7:0] color;
wire [7:0] colour; 
InoutConnect #7 a1(color,colour);

Now, color and colour are two names for the same signal.

SystemVerilog added the alias construct to do the same thing without needed to create a separate module.