[Coco] reading the ROM on a CoCo 3

[Robert Gault]

Mike Pepe wrote:
> Hi guys,
> 
> Does anyone know how to read the cartridge ROM directly on a CoCo 3?
> 
> Whenever I try, I read the RAM copy. There is no activity on the cart's 
> ROM select.
> 
> I tried setting $FF90 to $8C, thinking that would switch off the MMU and 
> go directly to the hardware, but doing reads results in nothing.
> 
> The only time I get read activity on that cart select pin is after reset.
> 
> What's the trick?
> 
> -Mike
> 

There should not be any problems but your question needs more details. 
Is there an MPI in use? If so, what slots are occupied and with what packs?

Keep in mind that the default setting for a Coco3 is all RAM. That means 
you probably want to switch to ROM mode when reading a pack. That means 
Basic should not be used to do the reading. Write a short ml program 
that goes to ROM mode, reads the pack, goes back to RAM mode, and then 
returns to Basic.