Re: Apple II Parallel Cards

["mdj" <mdj.mdj@gmail.com>]

Greg Andrzejewski wrote:

> Exactly. I/O from the parallel port doesn't require ECP/EPP. On IBM's SPP, 4
> status lines are used to read a nibble from a device (creatively termed
> 'nibble mode'). A decent description can be found here
> http://www.fapo.com/nibble.htm. Using nibble mode allows the SPP to
> interface with more than just printers (tape drives, scanners, zip drives,
> etc).

This is the old HP Bitronics mode. In theory the cards Michael
mentioned have the means to control such devices, assuming all the
control lines are wired.

> The problem is the lines used by nibble mode aren't present on most Apple II
> parallel cards. If there was a card that effectively duplicated the function
> on an IBM SPP, all that would be needed to take advantage of so many
> parallel I/O devices being dumped daily is appropriate software.
>
> Thus answering the question that prompted this inquiry, "Why can't I use a
> parallel zip drive with my Apple IIe?"

The software would take some writing, but it's possible. Essentially
you'd need a loadable driver than parked itself in one of the upper
banks of a RamWorks card and patched itself into ProDOS as a SmartPort
driver. Doable, but tricky. It's far, far easier to use SCSI for this,
and the SCSI cards are probably more common than the parallel cards
that provide sufficient signalling.

I'd like to see it done though, if just for the 'cool' factor.

Matt