[Coco] Cartridges that use SCS decoding

[Darren A]

On Thu, Mar 9, 2017 at 1:41 PM, Zippster wrote:

> Good point Jim.  I do something similar with the PSG.
>
> There is a bit in the control register (SCS space), that software must
> explicitly
> set to enable writes to CTS space and enable SLENB.
>
>

Depending on what you're using the CTS space for, another possibility to
consider is keeping a shadow copy of the Map Type setting (FFDE/FFDF) to
arbitrate between internal RAM and the external device memory.

You could also keep shadow copies of the MC0 MC1 bits from FF90 to know
which addresses are currently considered to be in CTS space on a CoCo 3.
To track MC0,MC1 you need to assert SLENB on all writes to FF90 for MPI
compatibility.


- Darren