4 Sep
2001
4 Sep
'01
10:38 a.m.
A) Anybody know anything about the company that
marketed these, as I don't
want to intentionally break any copyright laws; but with no info on the
internet & the extreme possibility of the company no longer existing, does
anyone think I'll be in trouble with the law WRT copyright laws? I'm mainly
just using the original as a pattern for (1) the signal names & pinouts,
and (2) the dimensions of the connectors & pins (I didn't have anything
else that had the ground pegs on either side of the connector).
If you are redesigning for YOUR use only, then at least in the US, there
is no copyright problem any which way (it falls under Fair Use).
The designs (when they get closer to completion) I will
have on my website
for free, but if I make several cards and someone else is dumb^H^H^H^H bold
enough to purchase one I would sell them for a small profit...
This is where you can get in trouble. If you make your mods available to
the public (even if for free), you can be seen as infringing upon the
owners rights. However, if the company has gone out of business, you
probably wont get in any trouble. But do NOT confuse out of business with
public domain, they are not one in the same, just because the company is
out of business or isn't selling the item any more, does NOT mean that
the item is public domain. They still have the rights to it, and can
choose how and where it can be made available. I personally still don't
think you will have a problem, but you will most likely technically be
breaking the law.
-chris
<http://www.mythtech.net>
6 Sep
6 Sep
2:54 a.m.
New subject: CoCo Xpndr1 Revisited...
Otay... I haz pix...
Here's what a CoCo Xpndr1 looks like: (warning, pictures might be kinda big
~~ 100k-ish)
http://www.30below.com/~zmerch/xpndr1/xpndr1-top.jpg
http://www.30below.com/~zmerch/xpndr1/xpndr1-bottom.jpg
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.
11:43 a.m.
New subject: CoCo Xpndr1 Revisited...
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8 Sep
8 Sep
4:26 a.m.
New subject: CoCo Xpndr1 Revisited...
More comments follow, but I've cracked some of my older Rainbow mags over
the last few days,and I found the company that sold the original XPNDR1
(and they had an XPNDR2 card as well, so you could still plug in your disk
controller...)
Robotic Microsystems
Box 30807
Seattle, WA 98103
The cards sold for $19.95 each, or $36 for 2 cards; at least that's what
they advertised for on page 139 of the January '86 Rainbow.
=-=-=-=-=-=-=-=-=-=-=-=-=
Rumor has it that Tony Duell may have mentioned these words:
Righto -- but I do want a ROM socket on my board, so I will have address
decoding (prolly for 8K, tho) to be able to access that.
I am *planning* on this being a large project... ;-)
As of right now, I have (2) 74LS244's buffering the address lines, but
there's more work on the way...
For a blick of what I currently have designed in Autocad (warning, it's a
130K jpg, and it's a *rough* design currently), go here:
http://www.30below.com/~zmerch/xpndr1/coco1.jpg
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...
Do you have a suitable signal to enable that 245 so that it only outputs
data onto the CoCo's data bus when chips on the Xpander are being read?
You don't want that 245 to contend with the ROM and RAM in the CoCo 
Shouldn't be a problem. I've buffered E and Q
many times without
difficulty. As a purist, I'd use 2 sections of the same chip to buffer
them (2 buffers in the same chip are likely to have similar propagation
delays) but actually it shouldn't matter much.
That'll be the 3rd '244, which I have to map in after some of the address
decoding...
Also look into the use of multiplexers ('151,
'150, maybe with one extra
NOT gate) as programmable 'gates'. I've used these to generate chip
selects, buffer enable signals, etc in the past.
Thanks for the advice. I found that Fairchild has a lot of datasheets on
the web (in pdf format) so at least I can get pinouts & whatnot fairly
easily...
I have used multiplexers in one project in the past, so I should be able to
figure out how to use them in this new context... but it might take a
little brainpower on my part. ;-)
Altho I do enjoy playing with 74'series chips, if anyone out there has a
cheap CPLD/PAL/GAL programmer they wanna part with, keep me in mind! I'd
love to tinker with those... :-)
Laterz,
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.
8:31 a.m.
New subject: CoCo Xpndr1 Revisited...
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ard＠p850ug1.demon.co.uk -
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zmerch＠30below.com