any idea what this schematic is?
ray at arachelian.com
Sun Dec 21 13:27:11 CST 2008
Ethan Dicks wrote:
> On Sun, Dec 21, 2008 at 1:42 AM, dwight elvey <dkelvey at hotmail.com> wrote:
>> Looks like RS422 interface.
> I don't know what the bus in the Lisa looks like, but the interface
> end, the bit that Dwight identifies as an "RS422 interface" will hook
> right up to a Mac (but I'd have to check to see if their DE-9 pinout
> matches the DE-9 serial pinout of the 128K/512K Mac board). The
> "Lisa-Mac Interface Card" legend at the top certainly suggests that
> it's a schematic for the card from the story. The circuit appears to
> be what one would need to add a Mac-compatible serial port to _some_
Right, the 6551 is a ACIA, which is an Async. Comm Interface Adapter.
So, the date on this is 1981, the 1982 version of the Lisa Hardware
Guide indicates that it did not at that time use the Z8530, but rather
used individual chips to implement serial ports (I recall a separate
chip for the baud generator). So based on that, if this is indeed that
interface, it sort of matches that they couldn't just hook it up to the
Lisa's serial port (perhaps they could at lower bps rates.)
The other interesting thing is the label - at first it looked like
ME1002-00, but it could also say MC1002-00, that middle line that would
make an E is a bit light, perhaps it was meant as a "C" - now this
matches the Mac motherboard labeling scheme here:
The DE-9 label matches the label on the original Mac 128 schematic:
Now what doesn't match is the card connector, it doesn't match the pins
on the Lisa motherboard - but perhaps this too was different in the 1981
>From what I recall, originally, the Lisa was supposed to be a 16 bit
text based computer, and only later, after the Xerox visit, did they
change things around.
So it might be that interface, it might be something completely
different - perhaps a prototype, or it might be mislabeled, or even a hoax.
I guess if someone knows how to contact Daniel Kottke, we could get
confirmation one way or another...
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