There was another thread about the same problem recently:
http://lists.bitchin100.com/private.cgi/m100-bitchin100.com/2024-September/090053.html
With a cable that looked like this:
http://lists.bitchin100.com/private.cgi/m100-bitchin100.com/attachments/20240925/4ad2aa75/attachment.jpg
See my 2 follow up responses in that thread.
You do need one twist in the wires on 102/200, but visually it's no
twist. top-to-top as you say.
But when you put two of the same gender connector back to back, that
actually produces a twist, because pin 1 of one connector can only match
up with either pin 2 or pin 39 of the other connector.
The cable in the pic then adds another twist with those short wires.
Double twist == no twist. Pin 1 is now going to pin 1, which is wrong.
To make it all extra excellent chefs kiss confusing... the T102 and T200
manuals label the pin numbers WRONG.
Pin 37 vs 38 is an easy way to tell what's *really* going on because
that one has RAMRST on pin 38 and NC on 37. and RAMRST is basic almost
like power. It's at 5v the entire time the machine is turned off but has
batteries, or at least 3v if relying on the internal memory battery. So
it's easy to check with a simple dmm.
The manuals say RAMRST is on 37 but it's really on 38. All pins are
actually swapped even for odd. It's just a numbering/labelling thing in
both the 102 and 200 manuals, and in all forms of the manuals, user
guide, service manual, tech ref. It's not related to how the pins need
to be twisted from the DVI to the 102/200. If the pins were labelled
correctly in the manuals, then pin1 from the dv needs to go to pin 2 on
the computer. Maybe that's why they labelled them wrong is so the
numbers would match the dvi, without actually changing the physical
pinout to actually match the dvi??
The good news is, the power pins are all doubled and symmetrical. Both
pins 1 and 2 have VCC, and both pins 3 and 4 have GND, so flipping 1/2
3/4 wrong won't hurt anything. Similarly,, both pins 39 and 40 are NC,
so if you flipped the connector over that way and put VCC into 39 & 40,
no problem. But it also means you can't use the power pins to tell if
you have it wired up correctly.
RAMRST could possibly be hurt, or hurt something, if you had a worse
error than you actually have. RAMRST is actually a power pin when the
machine is off, keeping external ram powered and disabled (active-low
chip-enable). So it's possible to hurt that if shorted to gnd, but just
doubling (aka cancelling) the twist won't hurt because the other pin is
NC, so you'd just be connecting RAMRST to NC. No problem. But if you
flipped it on the other axis so 1 & 2 went to 39 & 40, that would put
RAMRST pin 38 on either 2 or 4, GND. But I don't think you could do that
since the connectors have polarity notches. The only error is in those
incorrect extra twist wires, which are only crossing the odds & evens,
not end for end.
Whoever numbered the pins in the 102 & 200 manuals... I hope they were
just an intern and got reamed and never did that again...
--
bkw
On 11/18/24 23:54, Michael Brutman wrote:
I know this is going to sound crazy but ...
On the M102 system bus connector Pin 1 is marked on the top side of
the connector next to the reset button. That means pin 37 should also
be on the top row - second pin on the top row of the other side near
the printer port.
If I probe a machine with a logic analyzer and press reset, pin 37
(RAM RESET) does nothing. It's neither negative or positive. It is
just dead. But if I probe what appears to be pin 37, I get the
expected behavior on the reset button - logic low that then goes high
while the button is being held.
The same thing is happening on pin 32 (RESET). If Pin 1 is marked
correctly then pin 32 should be on the bottom row, That pin is active
and constantly changing state, so it's clearly not reset. But pin 33
(INT REQ) would have that behavior. Moving to what should be pin 31
(top row) shows logic low normally and logic high when I hold the
reset button.
Is the IO Bus on my machine wired with the pins already reversed?
On Mon, Nov 18, 2024 at 7:22 PM Jerry Davis <[email protected]> wrote:
Seems to be a cable/connector issue.
I repeated the sequence you described on the M100 and DVI that I
have here and BASIC loads and starts as expected.
I have a ribbon cable with a broken signal pin at the M100 end and
my M100 does what yours does when I use that cable. Which makes
me think you may have a cable problem.
Jerry
On Mon, Nov 18, 2024, 7:20 PM Michael Brutman
<[email protected]> wrote:
I powered on the M102 first, then the DVI. After the copyright
message came up I tried the reset button, power off and then
power on, and a cold start. The machine restarted but the
amount of free memory remained the same and the DVI disk light
did not turn on. I'm fairly certain the DVI is not seeing the
reset signal from the M102.
Going to BASIC and using SCREEN 1,1 fails because I'm still on
the built-in BASIC at this point, as DISK BASIC never got
moved into the memory on the M102.
-Mike
On Mon, Nov 18, 2024 at 3:20 PM Jerry Davis
<[email protected]> wrote:
After executing the power-on sequence and getting the
"Microsoft" message, did you execute the BASIC command
"SCREEN 1,1" from the Model 102?
The above command switches output to the CRT on the DVI
and displays the key labels at the bottom of the CRT.
Jerry
On Mon, Nov 18, 2024 at 11:39 AM Michael Brutman
<[email protected]> wrote:
I've tried all three methods - power off/power on,
Reset, and cold start. There is no difference. Also,
the two machines have no options or expansions that
would alter their behavior.
The technical service manual has a reasonable
troubleshooting guide which gives specific pins and
behaviors to look at. I'd still like to find a known
good cable before breaking out an oscilloscope, but at
least the schematics and behaviors are documented.
The length of the cable is kind of freaking me out a
little bit - for a bus that's a long stretch. Do you
know the length of the original factory cable?
-Mike
On Mon, Nov 18, 2024 at 9:19 AM Royce Taft
<[email protected]> wrote:
One other thing you could try is a cold start
(CTRL+PAUSE+RESET). It will wipe all your 102’s
memory, but maybe it will help?
Royce
Sent from my iPhone
On Nov 18, 2024, at 08:34, Michael Brutman
<[email protected]> wrote:
I had checked the connectors and pins before I
wrote, and I was even going to check for
continuity on each pin but that's going to take a
while and be error prone with 40 pins. The
connector on the underside of the DVI has the
snap-in latches which are engaging. I can't push
any further and I haven't bent any pins. The
cable is new from Gregory (Arcade Shopper), so I
don't have a lot of reason to suspect it.
Besides trying two different 102s I've also tried
batteries and wall power for the 102s, and I even
upgraded one to max out the RAM just in case I
was missing a memory requirement.
The DVI unit itself was pristine on the inside
when I first looked at it. I'll have another
peek inside to check the connector; perhaps it
experienced some trauma and there are broken
traces on it. But I really don't want to look
for problems where they are unlikely or fix
things that are not broken .. I've learned that
every time I disturb something there is risk
involved.
Is there anybody in the Seattle area (northern
suburbs) with a known good cable? If I can
eliminate the cable as a possibility then there
is only the DVI connector, as the rest of it
seems to function normally.
-Mike
On Mon, Nov 18, 2024 at 7:10 AM Royce Taft
<[email protected]> wrote:
When I had this issue, it turns out I hadn’t
snapped the connector in fully on the
underside of my M100. I would disconnect it
and ensure no pins became bent and flattened
out. If the pins look good, carefully replace
the connector and snap it firmly into place.
When making my cable, to figure out the
location of pin 1 on the M100 and the DVI, I
think I used a multimeter and the pin outs in
the various manuals to look for ground pins
which gave some insight into the orientation
of the connectors.
Seeing “please wait” followed by a Microsoft
copyright is a very good sign that your boot
disk was successfully read.
Royce
Sent from my iPhone
> On Nov 17, 2024, at 21:20, Michael Brutman
<[email protected]> wrote:
>
>
> Ok, here is the part I hate ... getting
things put together and then not having it work.
>
> I'm using Greg's cable kit with a Tandy
102. I have the twist adapter on the 102
side, red stripe oriented as in the pictures
on the Wiki. (The red stripe closer to the
'S' of "System bus".) That goes into the IDE
ribbon cable, which is connected to the DVI
also using the orientation in the pictures
from the Wiki.
>
> I used Teledisk to create the disk image.
I powered on the 102 first, as per the DVI
user manual. When I power on the DVI I get
the "Please wait!" message, and then I get
the Microsoft copyright message. All of this
is good so far.
>
> Where things fail is when I try to load
disk BASIC onto the 102. The instructions
say to use the Reset button or to power the
machine on and off. Neither has any effect,
and I've tried it with two different 102s.
>
> What am I missing here?
>
