writing the Top module file

[Smith]

Hi,all.

I'm now designing a system which consists of several modules
and now i'm going to combine all the modules into the Top module design
file.

my question is does the top module file need to declare all the inputs
for each of the modules in the system, even though some of the inputs
of the modules are not coming from the previous module in the system?

Thanks for any help.

 

[Ralf Hildebrandt]

Smith wrote:

my question is does the top module file need to declare all the inputs
for each of the modules in the system, even though some of the inputs
of the modules are not coming from the previous module in the system?

Pardon?

The I/O signals of the top module are the pins to the outer world. You
decide, what pins are necessary.
I/Os from submodules are just internal signals that are needed to
connect submodules. What you do with internal signals, is your decision.
You may use them simply as internal connections or you may feed them
right to a topmost I/O pin.

A simple example:

--------------------
| ----------- |
-|---|inner_mod_1|----|-
| .-| | |
| | ----------- |
| *---------------. |
| ----------- | |
-|---|inner_mod_2|-* |
| | |----|-
| ----------- |
| top_mod |
--------------------

The top_mod does not care, if there are deeper hierarchies in
inner_mod_1 or inner_mod_2.
-> Every module has to connect every signal, that it can see.

Ralf