[Coco] MC6847 External Character ROM

[RETRO Innovations]

On 1/22/2015 11:32 PM, Zippster wrote:
> Well, I think I’ve found an abundance of unused locations if I’ve read the SAM
> datasheets, CoCo2 memory map and schematic correctly.  96 unused addresses
> listed as ‘reserved for future use or special io’ (FF60-FFBF).
> They don’t seem to be used by either the 74LS783 or 74LS785 SAM versions,
> so if they do actually light up y7 as they should on the 74LS138 (IC11) I can
> use them for all kinds of stuff.

Would it be possible to set one byte as an MMU to remap the char rom 
(ram) into another slot in the Coco?