How Can I Connect Multiple Modules in Verilog?

[david90]

Say I have 3 modules and I want them to connect them together (make them work together. Ie, output of one module would go into another etc.), how would I do this in verilog?

 

[chroot]

Create a top-level module that instantiates each of the three modules, and connects them with wires.

- Warren

 

[david90]

instantiates ?[?] [b(] U mean create a 4th module that connects the 3 modules together with wire? Can u elaborate on the "wire" part?

 

[chroot]

Yes, make a top level module which creates instances of the three lower modules.

The "wire" keyword, surprisingly, makes wires.

Here's a simple example with two modules, sub_a and sub_b, and a toplevel module which connects their inputs and outputs.

module sub_a ( in, out );

input in;
output out;

...

endmodule

module sub_b ( in, out );

input in;
output out;

...

endmodule

module toplevel;

wire one;
wire two;

sub_a sub_a_instance ( .in(one), .out(two) );

sub_b sub_b_instance ( .in(two), .out(one) );

endmodule

 

[david90]

My interpretation of ur code sub_a input is wired to sub_b output. Am I right?

 

[chroot]

Yup, it just wires the inputs of each to outputs of the other. Of course the names are not exactly well-chosen. I just wanted to demonstrate the concept.

- Warren

 

[david90]

Thanks you've cleared it up a lot. I have another problem. I'm trying to write a code for a chip that has 3 modules and the output of those three modules are connected to an AND gate. How do I go about doing that??

 

[chroot]

...

wire sub_1_output;
wire sub_2_output;
wire sub_3_output;

wire and_output;

and and_gate (and_output, sub_1_output, sub_2_output, sub_3_output);

...

- Warren

 

[david90]

now that i have a one bit ALU, how would I link 4 of them together for a 4bit ALU? same method?

 

[Guybrush Threepwood]

yep, just be careful not to mix up the carry signals...