Visualising program structure

Hi,

I'm trying to draw some sketch illustrating how different parts of my
program are related and what are data passed from one part of the
program to another, e.g.,
the subroutine fA defined in the module A calls the subroutine fB
defined in the module B and passes an argument of the derived type tC
defined in the module C, etc. My purpose is to optimize the
organization of data, so that the data is arranged in different modules
in a way minimizing the dependences between them. Are there any
standards how such diagrams should be plotted and what notations are
used? The flowcharts that are used for algorithms do not seem relevant
in this case, because I'm using a standard and pretty straightforward
algorithm and I need to vizualize only the data dependencies. UML
maybe? Is it appropriate in this case?