[Coco] How SLENB works ?

[Matthew Stock]

On Sun, Jul 20, 2014 at 10:42 AM, Luis Antoniosi (CoCoDemus) <
retrocanada76 at gmail.com> wrote:

> There is this drive emulator for the Atari:
> http://www.whizzosoftware.com/sio2arduino/index.html
>
>
It looks like the Atari uses a serial protocol, which is both slower and
more amenable to this kind of interfacing.


> Maybe I should double buffer the data lines if I wan't them to be
> bi-directional, being the arduino buffer controlled by the the arduino
> itself
>

I did something similar in my initial design.  If you really just want to
fake ROM, you can use the Arduino to load an external memory chip while
holding HALT for the Coco.  When programming is complete, release the
address/data lines and turn it over to the Coco.  If you need it to be more
interactive, either dual-port RAM or something similar could work.  I did
this using a CPLD, but it could be done with discrete logic.  Some early
attempts at both the Arduino and the CPLD code are at
https://github.com/mattstock/cococpld.  I've been working on something else
recently, but you may find some useful code there for your projects.

Feel free to contact me directly if you want to discuss any specifics:
stock at csgeeks.org.
  -Matt