🚀 go-pugleaf

I am present in the process of undertaking a project, in which I need 
to interface a standard 6821 PIA to an Atari ST.

However, as with every project, I have a problem.

My problem lies in the fact that the cartridge port has no R/W line,
and that the GLUE chip does not allow you to write to ROM space anyway.
(Hence I cannot use the Rom3/Rom4 lines as dummy R/W lines) 

At the same time I see products on the market (such as Robot Arm Controllers)
which use the cartridge port, and obviously find some way of getting around
the above WRITE problem.

If Anybody (but anybody) has had past, present or planned future experience 
with interfacing to the Atari, Please could you drop me some helpful hints.

Yours (a little bit more that truly) Sam.

p.s. Is the DMA port a viable alternative ???