Re: Documentation wanted

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

On Nov 5, 10:48 pm, Steven Hirsch <snhir...@gmail.com> wrote:
> mdj wrote:
> > Understanding of the hardware protocol used to communicate with
> > SmartPort devices (Like the Unidisk 3.5" or the Chinook). You can grab
> > this from the aforementioned reference.
> > Understanding of the Smartport software protocol. I found the
> > disassembly of the IIc ROM in any of the reference manuals post the
> > original an excellent guide for this.
>
> > What's not documented at all as far as I can tell is the IWM, and
> > that's where it gets tricky. To get further, you're going to need
> > either a logic analyser, or very patiently reverse engineer the
> > encoded packets.
>
> I was always under the (perhaps mistaken) impression that the IIc used direct
> hardware twiddling for hard-drive support on the Smartport.  In other words,
> that it bypassed the firmware and IWM chip with bit-banging.
>
> Will have to take a look at that documentation.

It's the Apple II world equivalent of the "Improbability Drive" :-)

Bit banging is used for negotiation, for instance to reset all devices
on a SmartPort bus and to perform a form of handshaking very similar
to rs232. Actual data is transmitted via the IWM in packets that more
or less match the smartport commands, in chunks that are checksummed.

They went out of their way to ensure data integrity and reliability on
relatively long physical smartport busses.

> If it's of historical interest, I still have the official "Protocol Converter"
> specification that Applied Engineering sent me when I was writing Unidisk 3.5
> support for the AE Z80 card.  Probably worth scanning and archiving.

If it covers more than just the firmware interface, it'd be well worth
having, but I suspect it doesn't as I have a similar sounding document
here; it was an addendum to the IIc reference manual after the unidisk
rom update, before the SmartPort naming convention was used.

Matt