Re: Unknown card. Anyone know it?

["Mark Cummings" <NOTfigjams@primus.com.au>]

Bart,

It is most definately a 32bit I/O card for experimental/custom work. those
6821's are PIA's which give you 16bits of I/O each. I have a home made one
with just one 6821 (==6820) PIA.
The LS138 is simply a 1 of 8 decoder chip, probably to access both PIA's
separately at different address ranges. BTW each PIA has 2 address lines,
normally A0 and A1 on the Apple bus, that are used to select each of the 6
registers in the PIA:
DDRA, DRA, CRA, DDRB, DRB, CRB.
DDRA is the Data Direction Register A
DRA is the Data Register A
CRA is the Control Register A
ditto for B.
It's a bit hard to explain how 2 address lines access 6 registers, but if
you do a search for the 6821 or 6820 on the net, you should find out the
Technical stuff on the chip.
The TL071 and TL074 are OP-AMPs IIRC (don't quote me on that, I could check
though).
I assume you would have 4 sets of I/O pins on the card with at least 8 pins
each. If so, this is where you would connect external digital I/O.
And the 74LS04 is an inverter (again IIRC) probably for address decoding.

HTH,

Mark


Bart <pilgrimer@syndicomm.com> wrote in message
37a199dfd285d836383c1d0f2e0f4938.14346@mygate.mailgate.org">news:37a199dfd285d836383c1d0f2e0f4938.14346@mygate.mailgate.org...
> I have a unknown card.  I do not have a digital camera handy so a
description
> will need to do:
>
> Marking in upper left corner: "Sunset Lab"  2 MC6821p CPUs at right angles
on
> the right side, a socket (16 pin) on the left top.
> 74 LS138n, 74LS04N, TL074CN (2) and one little TL071 chip on it scattered
> around the board.  4 switch DIP on the left top.  on the left bottom is a
15 by
> 9 array of holes (like a project card; they are aranged in a grid you
could
> plug standard sized parts into, and there are no connection betwween these
and
> the other traces on the card).  The rest of the board has a standard set
of
> traces to the scattered parts.  Any ideas folks?
>
> -Bart
>
>
> --
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