More digging later has revealed three Usenet articles from the same week
in 1997 of a product called the "BASICON MC-1N REV A" - there's no vendor
name on my INS8073 board, but the part number matches.
The Basicon, Inc. website says they are the victim of the current economic
times. I've written the repair service listed on their page, but we'll see
if they answer.
In the meantime, has anyone heard of Basicon? Might their "MC-1N" be the
same as what I have (INS8073, 2K SRAM, 8255...)? I've figured out most of
the circuit - what has me stumped is that the chip selects are all run
through a 74S188 burned as an adress PROM (its address lines are attached
to A15-A11 of the CPU, and its data lines go to various chip selects on
the board). I've tried building a circuit to manually dump the PROM (it's
only 32x8), but no success there - all the bits read '0', which means
"always selected" for all devices... clearly not correct. Once I figure
out where in memory the MM58174A and 8255 are, I can do more than enter
simple BASIC programs. I'd like to see if there's room in the memory map
to add more SRAM - there's stuff I'd like to port from my collection of
PET programs that would need more than 2K (especially since the 8073
doesn't appear to tokenize its BASIC code when it stores it in RAM or ROM).
I've tried writing a program to read every Nth location between the top
of RAM and the top of memory space (the RAM, I've already proven, is at
the standard address of $1000)... because of the way the INS8073 determines
its baud rate (110 bps in this case :-P), "empty" locations read back
"182" - no matter where I look, though, I can't get any locations outside
of RAM space to answer back with anything else.
I'd love to get a manual for this, but there just doesn't seem to be that
much information on the 'net about it (if I _have_ that particular product).
I'm hoping that it is one of these... it's a pretty neat board... 24 I/O
lines out the front, 2K of SRAM and either 2K or 4K (2716 or 2732) of ROM
and a clock/calendar. There's even optional battery-backup for the clock
chip and the SRAM (just add 3V-5V to a particular pin on the serial/power
connector).
Thanks for any leads.
-ethan
--
Ethan Dicks, A-130-S Current South Pole Weather at 25-Apr-2004 10:10 Z
South Pole Station
PSC 468 Box 400 Temp -60.3 F (-51.3 C) Windchill -114 F (-81.09 C)
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Ethan.Dicks_at_amanda.spole.gov http://penguincentral.com/penguincentral.html
Received on Sun Apr 25 2004 - 05:30:46 BST