Searching \ for 'Reset Curcuitry (Paul)' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/index.htm?key=reset+curcuitry
Search entire site for: 'Reset Curcuitry (Paul)'.

Truncated match.
PICList Thread
'Reset Curcuitry (Paul)'
1994\11\10@030208 by crocontroller discussion list

flavicon
face
>
> I've got a SIMILAR type of question.....  The databook says that when
> powering up a PIC, Vdd must start from 0V.  I've found this, unfortunately
> to be correct.  Is there any way that you guys can think of to implement
> an inexpensive circuit to bring the power to 0V QUICKLY after power is
> disconnected so that you can QUICKLY power back up instead of waiting for
> the PIC to drain your power supply caps?
>
Use a DS1231 to get a reliable Power-On-Reset. It's esecially useful
when you use the 16C71 whose POR doesn't work...
Anyway; this way is probably cheaper than convincing the power supply
to go down to 0V before power-up.

/Tomas

spam_OUTtomasTakeThisOuTspamopq.se

1994\11\10@092834 by crocontroller discussion list

flavicon
face
> Use a DS1231 to get a reliable Power-On-Reset. It's esecially useful
> when you use the 16C71 whose POR doesn't work...
> Anyway; this way is probably cheaper than convincing the power supply
> to go down to 0V before power-up.

I can't find these in any of the catalogs I have with me - how much do they
cost in low quantities and how may pins do they have?

--

           -- Paul Greenwood --  (.....pabloKILLspamspam@spam@austin.ibm.com)

Any small object that is accidentally dropped will hide under a
larger object.

1994\11\10@204047 by crocontroller discussion list

flavicon
face
The suggestion of a DS1231 is a good one, but......

I've had dreadful luck with Dallas Semiconductor parts.
They've gotten a reputation for "cool stuff that blows
up in production volumes". I might suggest the Maxim
MAX705 reset chip, since it's available, cheap and
as far as I know, reliable.

Not to bash DS excessively, but I've just not had really
great luck with their stuff. Multiple part types, over
a period of years, at several different companies.

Be forewarned....

Mark G. Forbes
forbesmspamKILLspamcsos.orst.edu
R & D Engineer

1994\11\11@011813 by crocontroller discussion list

flavicon
face
>
> > Use a DS1231 to get a reliable Power-On-Reset. It's esecially useful
> > when you use the 16C71 whose POR doesn't work...
> > Anyway; this way is probably cheaper than convincing the power supply
> > to go down to 0V before power-up.
>
> I can't find these in any of the catalogs I have with me - how much do they
> cost in low quantities and how may pins do they have?

8 pins but I don't know the pricing. It's not very expensiv though.

/Tomas

.....tomasKILLspamspam.....opq.se

1994\11\11@100619 by crocontroller discussion list
flavicon
face
> The suggestion of a DS1231 is a good one, but......

OK - there has been a misunderstanding - the problem I'm having is with
Vdd not starting at 0V.  I have an RC circuit to delay the reset line and
I think that my problem is with Vdd.

>From the 1993 "Microchip Data Book", on page 2-25.  In the bottom right-hand
corner, the paragraph reads:

"To summarize, the on chip power-on reset is guaranteed to work if the rate
of rise of Vdd is no slower than 0.05V/ms.  It is also necessary that the
Vdd start from 0V."

This DOES seem to hold true for what I am doing.  If I reduce my Vdd to 3
volts, the uC stops functing.  I can then increase to 5V and ramp up reset
through an RC network and it does not reset correctly.

--

           -- Paul Greenwood --  (EraseMEpablospam_OUTspamTakeThisOuTaustin.ibm.com)

The Crown is full of it!
               -- Nate Harris, 1775

1994\11\11@120734 by crocontroller discussion list

flavicon
face
>This DOES seem to hold true for what I am doing.  If I reduce my Vdd to 3
>volts, the uC stops functing.  I can then increase to 5V and ramp up reset
>through an RC network and it does not reset correctly.
>            -- Paul Greenwood --  (pablospamspam_OUTaustin.ibm.com)


Why, pray tell, do you reduce Vdd to 3 volts and then increase back to 5V?
And by what means?

- JohnR

--
John R. Haggis            @spam@haggisKILLspamspamnetcom.com
Millennium Research
(408) 269-1814 vox
(408) 269-9323 fax

1994\11\11@123715 by crocontroller discussion list

flavicon
face
Dallas makes a 3 pin TO-92 device that will hold reset until
power is stable. It will hold reset low when power drops below
usable levels. I have used it without any problems. My data
books are at home and I don,t remember the part number or the
threshold levels. Call your local Dallas rep. or dist. and
SOLVE this problem.

Brian

1994\11\11@233349 by crocontroller discussion list

flavicon
face
>
> I've had dreadful luck with Dallas Semiconductor parts.
> They've gotten a reputation for "cool stuff that blows
> up in production volumes". I might suggest the Maxim
concur.  I love all of Dallas' stuff but I have had to repair too many
boards that have had one of their chips on it.  Except for thier clocks.

later
       John
-----------------------------------------------------------------------------
John Johnson  Team OS/2 member | KILLspamjohnsonjKILLspamspambga.com | RemoveMEjohnsonjTakeThisOuTspamutdallas.edu
                  C&H Technologies VXI Plug N' Play member
-----------------------------------------------------------------------------
And the Seventh version of OS/2 raised into the air its bow of blue steel and
cried," It. Is. Done."  Around him lay Bill Gates and Microsoft apps.  Their
evil in this world at an end.
                                       Revelations of InfoWorld, Oct 11 1994

1994\11\14@094609 by crocontroller discussion list

flavicon
face
> Why, pray tell, do you reduce Vdd to 3 volts and then increase back to 5V?
> And by what means?
>
> - JohnR

I can't remember if I answered this already so here goes (again).  I have a
regulator on my board and a big capacitor (10uF) to keep out noise, spikes,
etc.  Well, I plug in my device, the cap. charges to 5V quickly.
When I unplug the device, the cap. takes forever to discharge because the
PICs use so little power.  The problem is that the device seems to not work
if - say, it's plugged from one computer to another or the cable is lengthened
or for whatever reason I unplug and replug the device.  I've been shorting out
Vdd and Gnd every time so Vdd will start from 0V but I'd like a better
solution.

--

           -- Paul Greenwood --  (spamBeGonepablospamBeGonespamaustin.ibm.com)

All true wisdom is found on T-shirts.

1994\11\14@094808 by crocontroller discussion list

flavicon
face
> Dallas makes a 3 pin TO-92 device that will hold reset until
> power is stable. It will hold reset low when power drops below
> usable levels. I have used it without any problems. My data
> books are at home and I don,t remember the part number or the
> threshold levels. Call your local Dallas rep. or dist. and
> SOLVE this problem.
>
> Brian

I checked this out but I really need something like a 5V regulator that will
pull its output to 0V when the input falls below a threshold.

--

           -- Paul Greenwood --  (TakeThisOuTpabloEraseMEspamspam_OUTaustin.ibm.com)

All true wisdom is found on T-shirts.

1994\11\14@095656 by crocontroller discussion list

flavicon
face
{Quote hidden}

You know, you're right - when I have a "brown-out", my reset line does
not actually reset since my Vdd line doesn't go to 0V.  I, however,
found the line in the databook that said Vdd must start from 0V for a
proper bring-up and stopped looking at the problem.  I guess that, I
MAY be able to ignore the line in the databook and use the reset pin
and the DS1231.  I'll give it a try - testing - testing - testing.....
Thanks...!!!

--

           -- Paul Greenwood --  (RemoveMEpablospamTakeThisOuTaustin.ibm.com)

All true wisdom is found on T-shirts.

More... (looser matching)
- Last day of these posts
- In 1994 , 1995 only
- Today
- New search...