You wrote, "with c/c++ it's simple, just setting the pointer to desired address", but that is not really correct. In C, setting a pointer to an integral value has "implementation defined" behavior for (void *), and is (formally) an error for any other pointer type.
You should expect to have to write some system-dependent mex code to perform this task. You should not assume that it will be possible to do as an unprivileged user; for example, Windows after XP makes it very difficult to access the parallel ports.
Is this task for the interactive MATLAB or is it for code being generated to run on a different processor such as one of the TMS or dPIC series?