On Sun, Apr 25, 2004 at 03:21:14PM +0100, Davison, Lee wrote:
> > I've tried building a circuit to manually dump the PROM (it's
> > only 32x8), but no success there - all the bits read '0',
>
> You do know the 74S188 is open collector outputs? You'll need
> pullups or the data will always read '0'
I did figure that out last night - I've started manually dumping the ROM.
It's a pain fiddling around five jumper wires on a breadboard - I took a break
after about 8 readings, but I did deduce the locations of the clock chip and
the PPI. There also seems to be an unused second RAM chip select (not routed
anywhere, nor pulled up)...
The memory map seems to be:
$0000-$0FFF not mapped (INS8073 internal ROM space)
$1000-$17FF 2K SRAM (6116)
$1800-$1FFF 2K alt SRAM (not in this circuit)
$2000-$7FFF empty
$8000-$8FFF 2K or 4K (ext. jumper) EPROM 2716 or 2732
$9000-$A7FF empty
$A800-$AFFF MM58174A clock/calendar
$B000-$B7FF empty
$B800-$BFFF 8255 PPI
$C000-$F7FF empty
$F800-$FFFF* Baud Rate Jumpers
* - internal RAM also mapped into this space, but those address don't seem
to get presented to the external circuitry
I wish there were a device programmer on station. I didn't think it was
worth shipping an extra 20lbs both ways, so I didn't send mine down. I
don't have any blank 78S188s anyway, but I don't see why I couldn't remove
the pullups and use a suitably programmed GAL 16V8. Shouldn't take long
to write up some simple equations for that, then I could put a 32K SRAM in
a socket adapter and run the extra address lines to it...
I do appreciate the tip, though.
-ethan
--
Ethan Dicks, A-130-S Current South Pole Weather at 25-Apr-2004 23:00 Z
South Pole Station
PSC 468 Box 400 Temp -59.1 F (-50.6 C) Windchill -120.7 F (-84.90 C)
APO AP 96598 Wind 16.2 kts Grid 346 Barometer 687.7 mb (10337. ft)
Ethan.Dicks_at_amanda.spole.gov http://penguincentral.com/penguincentral.html
Received on Sun Apr 25 2004 - 18:17:13 BST