IBX PCMCIA 'port'

[Ralph Barrett]

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. 

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.

Programming pins are not connected at all:-( If you wanted to programme
a 5volt linear flash ROM you would have to add some extra hardware to
drive these programming lines.

Oddest thing (IMHO) is the Chip Enable lines on the socket. CE1 p7 is
the same signal used by the operating system ROMS, as is OE p9 (Output
Enable). CE2 p42 does not appear to be connected to anything in the Bush
Box - this is what is odd. According to the spec I'm reading for 4mByte
linear flash, you need to be able to control both CE1 and CE2 to
read/write data to the PCMCIA flash card.

At present it appears that the PCMCIA socket is wired in 'parallel' with
the operating system ROMs (i.e. might be designed to be used to replace
the ROMs i.e. ROMs removed). This might be useful for Vincent's Linux
development. PCMCIA linear flash ROM card would provide the 16-bit bus
data-bus. Risc-OS normally used a 32-bit data bus. In the IBX (and
RiscPC/A7000) there are two 1M*16 operating system ROMS providing D0-15
and D16-31).

I intend to solder a PCMCIA socket onto one of my IBX boards. Expect to
find a way of being able to read a linear flash ROMs, although I'm
probably going to have to cut the track to CE1 and wire this somewhere
else.

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

Ralph

ps. My IBX music box runs fine with the 64Mhz mod (thanks Vincent).

pps. Apart from '*co. mouse. 3' in my AUTO boot file on my zip disk,
I've still not found a way of setting the mouse type to 3. Writing '3'
to the flash ROM at address &02104DC4 offset &1D ('mousetype' in the
tags file) does not work. Set back to 5 at next boot up.

ppps. Nice to see this board flourishing again...