Re: Apple ][ using PC floppy

[vladitx <vladitx@nucleusys.com>]

On Dec 31, 7:46 pm, aiiad...@gmail.com wrote:

> It would be interesting to hear ideas for co-processing.  there is no
> I/O on the board besides the SD/MMC card and the serial port...  I
> haven't looked at the schematic yet, what is the AVR connected to?
> can it put data on the apple II bus?

AVR exchanges data with 6502 through the CPLD.

I wonder if accelerating D. Schmenk's 3D game would be viable, but
he's the only one who could tell. :-)

Basically, data exchange goes like this:
  - 6502 sends command and whatever data by writing to I/O address
  - AVR processes it
  - 6502 polls a bit at I/O address to see if processing is done
  - 6502 could optionally read back processed data

The 6502 CPU is free to do other stuff before polling the "ready"
flag. With carefully designed data transfers, processing time and
loops this could be of benefit. Hence the "co-processing".