I never owned one, I only know because I've just spent the last 3 or 4 days putting together a site to browse my mirror of pigwa.net (the Atari software archive site), and I happened to be using the 'Projects' directory for my testing.

If you:

1) go to http://atari-archive.net/

2) Double-click the 'Cloud drive' icon to open the window

3) Double-click on 'Projects', then 'Turbo Freezer 2005 & 2011' [1]

You can see the project, including a PDF of English documentation in the turbo-freezer-2011 subfolder.

[1] The icon isn't wide enough for the entire filename but it's obvious what's what. There's an 'As list' mode if it bothers you :)

I think the Atari version uses the /IRQ on the parallel bus, I know you can do some funky stuff with that - like take over the bus from the CPU (by keeping it in halt) and as long as you respect Antic's bus cycles (the true master of the "cpu" bus) you can read/write to RAM and do whatever you want.