[Coco] Coco Digest, Vol 53, Issue 4

[Mark McDougall]

Ty S wrote:

> If this unit is given a small amount of memory and a uC, it could keep
> track of the contents of the 6809's registers by decoding & processing
> the instructions in the same way as the 6809 (as they relate to changing
> the values in the registers).  AFAIK, this would be the most transparent
> way to "peek" at the registers without interrupting the execution cycle.
> I'll put it on the proposed feature list for now, but I don't want to
> make any promises.  My time is limited at the moment.

How do you plan on mirroring the interrupt behaviour? You have no way of 
knowing exactly *when* an interrupt is latched by the 6809, and you could 
lose all synchronisation between the emulation and the processor...

Why not replace the 6809 in the coco with an FPGA running a modified soft 
core that had debugging capability built-in... of course there's the voltage 
level issues, and it wouldn't be cheap...

Regards,

-- 
|              Mark McDougall                | "Electrical Engineers do it
|  <http://members.iinet.net.au/~msmcdoug>   |   with less resistance!"