[Coco] SCS - $FF40 behavior

[RETRO Innovations]

On 10/15/2015 8:45 PM, Chad H wrote:
> Well I confirmed the ground triggering of the SCS line by accessing $FF40 is detectable by my o-scope.  Going to mod one of my 512K EEPROM boards and its external Atmega328 driven controller so that the Microcontroller can detect the SCS trigger.  Then going to combine that with a modification to the 25 byte assembly .BIN loader we came up with last year and 'hopefully' allow .BIN loads from EEPROM in excess of 16K by loading it in 8K segments at a time :)  This method, if it works, would keep the EEPROM map area within the &HC000 - &DCFFF 8K space and function for the CoCo 3 as well.   I still don't have a CoCo 3 to verify that $FF40 triggers the SCS line by default on those machines. Any details would be helpful.  If we can load a 512K EEPROM full of .ROMS of any size, and of .BIN's of any size, I think we can remove  most of the downsides people have pointed out.  With the external controller it could be left plugged in and remote bank-switched by the controller to reduce wear on the cartridge port.  With larger .BIN file support it could be more useful for these.   Of course, I will have to get re-acquainted with the assembly .BIN loader :/
>
> - Chad H
> http://sites.google.com/site/cbhlab101/
I can confirm that SCS is low on Coco3 when accessing $ff40, but only 
after banking in the ROMs.

Jim