Reset button for CBM 3032
tcrass
we used to have a (one!) CBM 3032 at school back in the late 70s/early
80s, and when I recently got the chance to purchase such a baby from
ebay, I just couldn't resist... Thanks to numerous instructions found on
the web, an amplifier and speaker was quickly installed for sound
output. However, in spite of intensive search, I couldn't find any
instructions on how to install a reset button to this kind of machine.
In contrast to, say, the C64, there seems to be not reset pin available
on any of the CBM's external interfaces. So does anyone have a clue
where the reset line might be accessible instead? (Or even better: Does
anyone know the exact circuitry for the "enhanced" reset button
mentioned in the FAQs -- the one with the capacitor, which also set the
DIAG line depending on how long the reset button gets pushed...?)
Thanks in advance for any help, and best regards --
tcrass
donni
If you have a look at the schematic on zimmers.net, you can see that
the reset timing is done with a LM555 timer ic.
If you install the reset switch over condensator C68 right beside the
LM555, that should do the trick.
Schema: http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/2001N/320349-1.gif
tcrass
sorry for the delay in replying -- I've been terribly busy over the last
weeks... Saying thanks for your reply is overdue - so: thank you!
However...
> If you have a look at the schematic on zimmers.net, you can see that
> the reset timing is done with a LM555 timer ic. If you install the
> reset switch over condensator C68 right beside the LM555, that should
> do the trick. Schema:
> http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/2001N/320349-1.gif
>
...the DIAG line doesn't come into play here, does it?
What I was actually interested in was the device described in:
--------8<--------
> Quote from Olaf Seibert from the PETdoc document:
>
> If you hold down the diagnostic sense line (user port pin 5), you'll
> end up in the monitor instead of doing the full reset thingie. A PET
> at our school's computer club had a smart thing with a switch wired
> to reset, and diag through a condensator. If you flicked it quicky it
> would reset; if you kept the switch in the alternate position a few
> seconds it would decharge the condensator, pull down diag, and when
> switched back you came back in the monitor.
--------8<--------
This quotation can be found hundreds of times on the Web, but I wasn't
able to find any further details about that magic circuit.
Regards --
tcrass
la...@portcommodore.com
In Programming the PET/CBM it refers to two reset circuits that can be
found in the September 1980 Kilobaud Microcomputing Article by Jim
Strasma... hmmm... aha! the PET Personal Cmputer Guide 3rd edition
(Part authored by Jim and Ellen Strasma) discusses a reset switch
circuit...
I'll try to OCR it.
donni
>
> - Show quoted text -
I have thought about that diag thing and came up with a solution.
I made a quick drawing of how I did it and made a scan of it.
http://img523.imageshack.us/img523/6805/resetdiagswitchge3.jpg
If you tap the switch you get a reset, if you hold it down you'll end
up in the monitor.
I have tried it on my 3032 and it works perfectly :-)
-donni
tcrass
> If you tap the switch you get a reset, if you hold it down you'll end
> up in the monitor.
> I have tried it on my 3032 and it works perfectly :-)
very nice -- and very brave, indeed! ;-) I came up with something
similar, but I didn't dare trying it out, since I'm not really an
electronics wizard.
What I keep wondering about: don't we need any resistors to limit
current? And how does the capacitor get discharged after the button has
been released?
> I'll try to OCR it.
Larry, that would be great! (Although a simple scan to jpeg would do,
wouldn't it?) (Just visited your website -- very nice! :)
Regards --
tcrass
ramswell
Hummm.
What kind of reset button are you looking for? I mean do you want to
reset the power, or do you just want to reset the I/O channel on it?
If you let me know which you are interested in doing, I can check
around and see what I can come up with for you.
Charles>8-Bit Designs
http://8bitprodserv.spaces.live.com
TELNET BBS: masterskingdom.dnsalias.org
la...@portcommodore.com
>
> I'll try to OCR it.
And here it is:
http://www.portcommodore.com/misc/reset.pdf
I had to PDF it as I wasn't at my web site editor and it had a very
necessary diagram (included)
Hope it helps.
Larry
tessaract OCR for Linux is great, it may be shell only but it is very
accurate.
donni
To be on the save side you can put a resistor in series with the reset
switch, but normally this is not necessary.
And the capacitor gets discharged with resistor R16 and port PA7 of
the PIA.
Regards,
Donni
tcrass
> To be on the save side you can put a resistor in series with the reset
> switch, but normally this is not necessary.
> And the capacitor gets discharged with resistor R16 and port PA7 of
> the PIA.
I see... thanks for the explanation!
All the best --
tcrass
tcrass
> I had to PDF it as I wasn't at my web site editor and it had a very
> necessary diagram (included)
>
> Hope it helps.
it definitely will, thanks!
All the best --
tcrass
P.S.
> tessaract OCR for Linux is great, it may be shell only but it is very
> accurate.
<sigh>If only my scanner was usable under Linux... </sigh>