CoCo Xpndr1 Revisited...

From: Roger Merchberger <>
Date: Thu Sep 6 09:54:20 2001

Otay... I haz pix...

Here's what a CoCo Xpndr1 looks like: (warning, pictures might be kinda big
~~ 100k-ish)

The scans aren't the greatest as I had no black paper at the time to reduce
the translucency of the board... but it'll give y'all a much better idea as
to what it is...

Now, the first thing I'm going to do is put on a 74LS245 bus transceiver on
the data lines, and a pair of 74LS244's to buffer the address lines...
right? Could I also use a LS244 to buffer E & Q? I wouldn't think that
shottky parts would impart much noise on a 1Mhz signal...

I also plan on adding:

A jumper/switch to enable the CART signal easily,

A row of jumpers to easily enable multiple address decoding (along with the
associated NOR's, NAND's & a well-placed 74LS138...)

and methinks that'll fill out "round 1" of the Merchalizer expansion board.
(No, I'm not really going to call it that. ;-)

Later on, I'd like to make an expanded version with 1 or 2 integrated
16550's and a couple A/D's already addressed in...

The board is *already* a lot different than what you see in the pictures,
with the addition of both a "hard-drive" PC power connector & a floppy-type
PC power connector, with a power LED for the external power supply & it's
jumper selectable whether or not you wish to use the CoCo's available power
from the cartridge port, or the external power supply. By the time the
AutoCad file hits my website, there will be no resemblance whatsoever, and
all the card will be is what it was to begin with: inspiration to make an
experimenter card "far beyond" (and IMHO much more useful) anything else
I'd seen floating around...

And -- the practice playing with chips that I get far too little time to do!

Anyway, dat's da stuff!
Roger "Merch" Merchberger
Roger "Merch" Merchberger   ---   sysadmin, Iceberg Computers
Recycling is good, right???  Ok, so I'll recycle an old .sig.
If at first you don't succeed, nuclear warhead
disarmament should *not* be your first career choice.
Received on Thu Sep 06 2001 - 09:54:20 BST

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