Re: IC tester card

[Erick Wagner <wagnere@netcom.com>]

MJMahon wrote:
> 
> Thanks for the responses I received on two other cards--here's the
> third, and most mysterious, one...
> 
> I recently rescued an Apple peripheral slot card labelled IC TEST CARD,
> copyright 1984 by Yih Lung.  It's a full-size card (8" long).  The card
> has a potted portion about 3" square which, in addition to the name and
> copyright, also has the (company?) name "Fairy" and two Kanji characters.
> 
> It has five 4016 DRAM chips and a 6821P microprocessor 

The Motorola 6821 is NOT a microprocessor.  It is a support chip that
goes by the name, Peripheral Interface Adapter (PIA).  That's a fancy
name for two 8-bit I/O ports (plus additional handshake lines).  Each
bit of each port (A and B) can be controlled via software to be
either an input or output line.

As the name/number suggests, this support chip was designed by Motorola
to work with their 8-bit 68xx series of microprocessors, although the
6821 (and older 6820) work just fine with the 65xx microprocessors.

In case you come across one, the 6522 Versatile Interface Adapter (VIA)
chip is a similar device but much more powerful (built-in
timers/counters).

Good luck!

Erick