Alt-BEAM Archive

Message #05292



To: "'beam@sgiblab.sgi.com'" beam@sgiblab.sgi.com
From: Wilf Rigter Wilf.Rigter@powertech.bc.ca
Date: Wed, 14 Jul 1999 18:05:13 -0700
Subject: [alt-beam] Re: automatic pnc



content-type: text/plain;

Hello David,

I feel a little guilty knowing that Bruce has invested significant effort in
his cold start circuit design but it all part of the learning game so here
is a some friendly competition:

Although not tested, I think what we have here is an instant auto Pulse
Neutralizing Circuit (PNC) which will force a single process at power up and
any other time at the cost of two 1N4148 diodes. It makes the assumption
that in a 4 Nv ucore you can have zero, one or two processes active at one
time. Since the PNC guards against the 2 process condition and since these
only occur as process pairs in 1 and 3 or 2 and 4, then adding the diodes
will neutralize the twin processes in 2 or 4 whenever a process is active in
1 or 3.

If you wish to guard against the more unusual zero process condition, you
can combine a Pulse Injection Circuit (PIC ( yikes! no flame wars please!))
and the function of 4 red LEDs for indication. This is done with the
addition of a capacitor and 1K resistor to inject a process into the ucore
should all processes for some reason die out (unusual). The PIC is actually
a 4 input AND gate made from the 4 LEDs together with the 1K pull up
resistor. When all processes die off all four Nv output will go high and the
output of the LED AND gate will also go high pulling the 1M resistors of the
Nv input high. depending on the value of each Nv time constant one Nv input
will cross the positive trigger level and the corresponding output will go
low effectively inject a process into the core. Simultaneously the AND gate
output drops since there are no longer four high input and the process
starts to circulate around the core with each LED lighting to indicate the
Nv which is currently active.

The additional 0.1 capacitor is there to deglitch the circuit Nv but is
probably not be necessary. Using a single 1K resistor instead of the normal
4 resistors for LED indication effectively cancels out the 2 additional
diodes and the capacitor and so it's fair to say that the PNC and PIC
functions comes for free. In addition, the time constants of the Nvs are
increased by a factor of 2 or more, since the 1M Nv resistors are referenced
to the forward voltage drops of the LEDs (should be about +1.2V) making it
practical to use smaller resistors or capacitors. The obvious applications
of voltage controlled Nv time constants was covered earlier in my ETC and
Servocore articles. The only restrictions for PNC/PIC is a minimum 5V
powersupply, a 74HC14 (not 74HCT14) chip and relatively low forward voltage
drop red LEDs. Be sure to terminate the unused inputs of the spare
inverters to 0V if not used for some other functions (like a 6Nv core).

This circuit comes quite close to my BEAM design target of "a linear
INCREASE in functionality with a linear REDUCTION in complexity" ie the
more I throw out, the more it does, which of course I hope is scalable to
"zero complexity=infinite functionality" (reductio ad absurdum =) .

enjoy

Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
tel: (604)590-7493
fax: (604)590-3411

<>


> -----Original Message-----
> From: David Perry [SMTP:davidperry@geocities.com]
> Sent: Tuesday, July 13, 1999 10:54 AM
> To: beam mailing list
> Subject: Re: automatic pnc
>
> great!
> Thanks heaps, but i have a few questions.
> Where do the diode outputs connect to, the input of the microcore
> inverters?
> What's that 3rd inverter along, is it the same as the others? Do i just
> use
> another 74hc14 for all of them?
> Great, this will really help, thanks again!!!
>
> David Perry
>
>
> Oh and Ben Morgan, when you sent that message EVERYONE GETS IT thats
> hundreds of people that get an even more cluttered up mailbox.
>
> -----Original Message-----
> From: Bruce Robinson
> To: David Perry
> Date: Wednesday, 14 July 1999 11:40
> Subject: Re: automatic pnc
>
>
> >> David Perry wrote:
> >>
> >> But i still can't work out how to make a circuit to automatically
> >> introduce pulses for one of the following ways:-
> >> *detect with logic circuits when the microcore has died out and
> >> restart it OR
> >> *just introduce a pulse when the circuit starts which i don't really
> >> want beacuse i don't know why the circuits died
> >
> >Hi, David. Here's my cold-start circuit which I posted a while back. It
> >starts your microcore up with one pulse, period. No waiting while extra
> >pulses die out, or any of that stuff.
> >
> >This one is 100% guaranteed. I have been experimenting with another
> >circuit which does the same thing, but only uses two inverters. It's
> >worked perfectly for me so far, just have to get it into GIF format.
> >
> >Finally, I think I can adapt this circuit to figure out if your
> >microcore has gone dead. Essentially, there would be one neuron with a
> >very long delay, that would be triggered by one of the neurons in your
> >microcore. As long as a pulse kept coming around to trigger it, the
> >delay neuron would keep getting reset. However, if all your pulses died
> >out, the delay neuron would eventually time out and send out a signal,
> >that could be used to start up your microcore again. This one's going to
> >take some thought, because I don't know how it will behave on startup.
> >
> >More to follow.
> >
> >Regards,
> >Bruce


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