From: Wolfgang Moser (womo_at_news.trikaliotis.net)
Date: 2006-11-27 19:48:33
Hi André,
André wrote:
>Womo wrote:
>> what's the difference to Mika Leinonen's 1581
>> "replica" board, the DCN-2692 floppy controller ?
>
> I did not know about this one. Anyway, my goal was to
> implement it using my CS/A65 bus system, so you can plug
> together boards as you want to.
Regarding your CS/A65.. sometime in the future,
when I get back some spare time, I'll start a
discussion about your coprocessor board.
I'm interested in possibilities to connect a
foreign microprocessor to a 6502 system
_without_ soldering out an existing 6502 from
the system. External circuitry shoult watch
the 6502's SYNC line, whenever the 6502 fetches
an opcode and some other conditions are met,
the RDY should be pulled to halt the 6502.
Then the external coprocessor could utilise
the bus. That's my current plan, don't know,
if it would be worth to be developed. Maybe
illegal opcodes of the 6502 (KIL instruction)
could be used as special copro "opcodes".
> Also I wanted to use a standard PC drive and cable.
That's why I mentioned Mika's project. He also
made his controller board supporting standard
PC disk drives.
With my modification to use a slimline FDD I
was able to circumvent the diskchange (or was
it Ready?) emulation circuitry since slimline
FDD carry both signals on different pins.
> However, using a small program to M-R the drive controller
> return codes and the CIA register, and reading the ROM
> listings I found the problem: The pull-down resistor for
> the drive ready was to large, so the CPU thought the
> drive was never ready (well, as the drive error message
> already said ;-).
Fine, nice to hear.
Womo
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