PIC 16F877 hangs up

Started by R Ramesh June 19, 2003
Hi all ,
I m designing a control box with PICs ,  My system work with 16F877 and 16F872  . After I switch on the system , after few minutes the 16F877 hangs up . It's display shows it, all values in the display hangs up already , But still 16F872 is working . Then I switch off the system it happens again and again . For your Information My control box contains 4 more different power supplies and on High frequncy driver and one more current control cicuit.And I found when I cover the box fully it heats up quickly , even i have placed 4  fans ,
Is it any reason to hangs up PICs?
If 16F877 hangs up due to heat then how come still 16F872 is working?
Can any body give some idea to debug
Thx ,
Ramesh




Is the oscillator still oscillating? Could it be a problem with the
crystal/capacitors?

How are the unused pins, if any, treated? Are they left to float as
inputs?

Is the device hot to the touch? Can the problem be resolved with a
spray can of cold gas?

Can the problem be induced with a heat gun, applied carefully?

Is there a crack in a circuit trace that opens up when the board
expands?

Does this system work perfectly when it is maintained at room
temperature? Or in a refrigerator, if it fits?

Have you tried a different '877? What type of programmer are you
using? Some are marginal in the way they program the chips. "Can
you veryify the programming over varying Vcc as mentioned in the
programming specification.

Stack overflow under some strange operating condition? Usually this
is a result of interrupt handling. --- In , R Ramesh <ramesh_21_in@y...> wrote:
> Hi all ,
> I m designing a control box with PICs , My system work with 16F877
and 16F872 . After I switch on the system , after few minutes the
16F877 hangs up . It's display shows it, all values in the display
hangs up already , But still 16F872 is working . Then I switch off
the system it happens again and again . For your Information My
control box contains 4 more different power supplies and on High
frequncy driver and one more current control cicuit.And I found when
I cover the box fully it heats up quickly , even i have placed 4
fans ,
> Is it any reason to hangs up PICs?
> If 16F877 hangs up due to heat then how come still 16F872 is
working?
> Can any body give some idea to debug
> Thx ,
> Ramesh > ---------------------------------
>



"How are the unused pins, if any, treated? Are they left to float as
inputs?"

I'm a newbie at this. The above statement caught my attention. I'm not clear
as to what float is. In my project (using 16c711 chip) I utilize all pins
except the RB3 pin. I left this pin unused. Will this cause me problems?
----- Original Message -----
From: "rtstofer" <>
To: <>
Sent: Thursday, June 19, 2003 8:06 AM
Subject: [piclist] Re: PIC 16F877 hangs up >
> Is the oscillator still oscillating? Could it be a problem with the
> crystal/capacitors?
>
> How are the unused pins, if any, treated? Are they left to float as
> inputs?
>
> Is the device hot to the touch? Can the problem be resolved with a
> spray can of cold gas?
>
> Can the problem be induced with a heat gun, applied carefully?
>
> Is there a crack in a circuit trace that opens up when the board
> expands?
>
> Does this system work perfectly when it is maintained at room
> temperature? Or in a refrigerator, if it fits?
>
> Have you tried a different '877? What type of programmer are you
> using? Some are marginal in the way they program the chips. "Can
> you veryify the programming over varying Vcc as mentioned in the
> programming specification.
>
> Stack overflow under some strange operating condition? Usually this
> is a result of interrupt handling. > --- In , R Ramesh <ramesh_21_in@y...> wrote:
> > Hi all ,
> > I m designing a control box with PICs , My system work with 16F877
> and 16F872 . After I switch on the system , after few minutes the
> 16F877 hangs up . It's display shows it, all values in the display
> hangs up already , But still 16F872 is working . Then I switch off
> the system it happens again and again . For your Information My
> control box contains 4 more different power supplies and on High
> frequncy driver and one more current control cicuit.And I found when
> I cover the box fully it heats up quickly , even i have placed 4
> fans ,
> > Is it any reason to hangs up PICs?
> > If 16F877 hangs up due to heat then how come still 16F872 is
> working?
> > Can any body give some idea to debug
> > Thx ,
> > Ramesh
> >
> >
> > ---------------------------------
> >
>
> to unsubscribe, go to http://www.yahoogroups.com and follow the
instructions
>
> ">http://docs.yahoo.com/info/terms/ >
>




It is recommended by Microchip that pins not be left floating as
inputs as it allows noise to enter the chip. So, you can define it
as an output and set it to whatever state you want. Some people have
a problem with that because, they believe, during debugging it may be
shorted to the opposite polarity and destroy the chip. Seems
unlikely to me but...

The other alternative is to define it as an input and pull it to
ground or Vcc with a resistor - say 20k or so. In this
configuration, even if it is shorted to Vcc or Ground nothing will
happen to the PIC.

So the theory goes.

--- In , "Bill Davis" <wdavis@t...> wrote:
> "How are the unused pins, if any, treated? Are they left to float
as
> inputs?"
>
> I'm a newbie at this. The above statement caught my attention. I'm
not clear
> as to what float is. In my project (using 16c711 chip) I utilize
all pins
> except the RB3 pin. I left this pin unused. Will this cause me
problems?
> ----- Original Message -----
> From: "rtstofer" <rstofer@p...>
> To: <>
> Sent: Thursday, June 19, 2003 8:06 AM
> Subject: [piclist] Re: PIC 16F877 hangs up > >
> > Is the oscillator still oscillating? Could it be a problem with
the
> > crystal/capacitors?
> >
> > How are the unused pins, if any, treated? Are they left to float
as
> > inputs?
> >
> > Is the device hot to the touch? Can the problem be resolved with
a
> > spray can of cold gas?
> >
> > Can the problem be induced with a heat gun, applied carefully?
> >
> > Is there a crack in a circuit trace that opens up when the board
> > expands?
> >
> > Does this system work perfectly when it is maintained at room
> > temperature? Or in a refrigerator, if it fits?
> >
> > Have you tried a different '877? What type of programmer are you
> > using? Some are marginal in the way they program the chips. "Can
> > you veryify the programming over varying Vcc as mentioned in the
> > programming specification.
> >
> > Stack overflow under some strange operating condition? Usually
this
> > is a result of interrupt handling.
> >
> >
> > --- In , R Ramesh <ramesh_21_in@y...>
wrote:
> > > Hi all ,
> > > I m designing a control box with PICs , My system work with
16F877
> > and 16F872 . After I switch on the system , after few minutes the
> > 16F877 hangs up . It's display shows it, all values in the display
> > hangs up already , But still 16F872 is working . Then I switch off
> > the system it happens again and again . For your Information My
> > control box contains 4 more different power supplies and on High
> > frequncy driver and one more current control cicuit.And I found
when
> > I cover the box fully it heats up quickly , even i have placed 4
> > fans ,
> > > Is it any reason to hangs up PICs?
> > > If 16F877 hangs up due to heat then how come still 16F872 is
> > working?
> > > Can any body give some idea to debug
> > > Thx ,
> > > Ramesh
> > >
> > >
> > > ---------------------------------
> > >
> >
> > to unsubscribe, go to http://www.yahoogroups.com and follow the
> instructions
> >
> > ">http://docs.yahoo.com/info/terms/
> >
> >
> >
> >