[Coco] reading the ROM on a CoCo 3

[Mike Pepe]

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