[Coco] ROM Cart registers

[RETRO Innovations]

On 1/31/2016 2:15 PM, Darren A wrote:
> On Sun, Jan 31, 2016 at 12:47 PM, RETRO Innovations <go4retro at go4retro.com>
> wrote:
>
> I am struggling to  think of a valid reason to strobe SLENB* when SCS has
>> not been strobed and the address is located in the $ff40-$ff8f range.
>>
>> Jim
>>
>
> It means you're claiming the address space for exclusive use and you don't
> need to make the effort to write an "MPI aware" driver. You completely
> decode addresses yourself so the device is always active, even when the MPI
> slot containing it is not. By asserting SLENB* you prevent other devices
> (those that require SCS) from responding and creating a conflict,
> effectively locking them out.
>
> SCS only covers the $FF40-FF5F range.  $FF60-FF7F were assigned by Radio
> Shack to various products. $FF80-$FFDF are allocated to the GIME on the
> CoCo 3.
>
> - Darren
>
I did not realize SCS stops at ff5f.  I'll update my code.  I was 
wondering why the registers failed the other night to respond to an 
access at $ff6x

I also understand the reasoning now, but it will make it difficult to 
co-exist with such products.

Jim




-- 
RETRO Innovations, Contemporary Gear for Classic Systems
www.go4retro.com
store.go4retro.com