Re: Commodore drives can be controlled on Apple II serial!

[Rubywand <rubywand@swbell.net>]

Cameron Kaiser writes ...
> 
> Rubywand <rubywand@swbell.net> writes:
> 
> >     If, as you say later, the C64 drives can be run from a PC COM port,
> >there should be no problem running the drive from a GS serial port.
> >Given information about which signals and codes the C64 drive needs, an
> >interface routine could be probably be written.
> 
> It's not the COM port, but the LPT port.

     That the COM port could be used did seem remarkable based upon a
look at the C64 port specs. It uses serial I/O plus there is a Serial
Service Request and the computer is supposed to furnish Attention and
Serial Clock outputs. 


> What you would need to do is
> program the GS with some support for the IEC serial bus protocol. I don't
> know how accurate the timers are in GS/OS (whether it steals clocks like
> a certain Intel-based GUI which shall remain nameless), so it might have to
> be done on the command line (Nathan could probably answer this question).
> The IEC protocol is ridiculously timing-sensitive.
>

     The interface could use the Annunciator outputs and two "Switch"
inputs from the 16-pin Game soucket on the motherboard. For the length
of a C64 disk drive cable, they may work okay.

     You would want to shut off all interrupts. At least for a standard
C64 connection, the interface does not need to operate at a very high
speed; so, it should not be too difficult to maintain correct timing.   
     

> ....
> 1571s were capable of fast serial communications using a special mode called
> 'burst' mode, however, and could communicate with the 128 at a much quicker
> rate than in 64 mode. So it might not be as slow as you might think.
> ....

     Could be. Whoever might do the interface porgram would want to know
about any special Burst Mode commands.


> 
> The source, btw, for the Star Commander, the PC program that allows
> connection to 15x1 drives through the LPT port, is becoming available, so
> that may clue potential GS programmers in.
>

     It sounds like a good place to start.
 


Rubywand