IBX PCMCIA 'port'

[Adrian Godwin]

>
> Whilst it is true that the PCMCIA port is not a full PCMCIA
> implementation, it possible that this might still be a useful port. In
> particular, it would not be too difficult to get linear flash ROM cards
> to work on this port IMHO. I have a few linear flash cards that I use on
> my Newton that I intend to try...
>
> I am sure that the unfitted 68-pin connector is intended for a PCMCIA
> socket. Most of the signals to this PCMCIA socket are unbuffered and
> shared for other functions in the bush box. 

A hunt around Google suggests that it might be the socket used on
the NC for expansion ROMs, and that they might replace rather than
supplement the internal ROMs. But I can't find any details of how
those ROMs are wired.

> However, ss long as you power up tghe IBX with a PCMCIA card already
> installed, and only remove the PCMCIA when switched off, you should be
> OK. Plugging in a PCMCIA whilst powered on might cause the IBX to crash
> (and burn?) - as the data and address lines are not buffered (unless
> PCMCIA cards take care of this???).
>
> PCMCIA (or PC Card) socket appears to have GND and 5v power wired
> correctly. 16-bit data is taken from the main ARM 32-bit data bus D0-D15
> (also shared by the operating system ROMs). Latched address bus LA2-LA23
> is connected to PCMCIA A0-A21 as expected. PCMCIA A21 and above are
> connected to some of the top data lines (i.e. ARM  D16-D31). Some other
> control pins are also connected to these top 16 data lines. Using the
> top 16 bits of the 32-bit data bus as a sort of control 'register' for
> the PCMCIA port should not be a problem.

How would you set the top 16 bits on a read cycle ? Write is easy enough ..

>
> Does anybody know for sure what the original plan for this PCMCIA socket
> was ? Does anybody have a copy of the RiscOS PCMCIA module ?

From the earlier comment it sounds as though they started with PCMCIA
and then changed some things (perhaps a cost reduction), so it might
need some serious bodging.


Some other possibilities :

ZIP PPA is SCSI via a parallel port adapter. ATA is SCSI command set via 
an IDE interface. So maybe it's feasible to make something that adapts
the parallel port zip connection onto something more modern, like an
IDE disk or a compact flash.

The FDC37C699 has a mode where it accesses a floppy via the parallel
port pins. This bizarre idea is intended for use on a laptop, where
an optional floppy connects to the parallel port. I think the A4
used such a chip, though I don't remember whether RISCOS supported it. 

There's a RAM filing system on the box, called cachefs. You have to
configure it to have some size (see 'help cachefs'), then you can 
write to it (cache:$). This gives somewhere to load a module from 
without mass storage, if you can get the module on there. This might 
be possible using the web browser (does it cache pages in cache: ?) 
or the webftp module (if anyone knows how to work it).

You can reset the box without power cycling it by shorting pins
5 (reset) and 6(ground) of LK5. I'm not sure yet if this provides
a soft 'break'-like function, but it's likely to be less destructive
to ram contents than power cycling.


-adrian