accessing internal nodes

you'll have to route internal signals to actual pins for the fitter.

You can do this via the assignments editor. Add a new entry, right click in the "to" box and click on node finder. You should be able to find singals in a similar way you'd find them in signal tap - then you can assign them to a pin. It might not let you do that though - and the only way I can think of would be to route the signal to the top level in the source code .