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2005-01-27 by tah2k
When enabled and timed out, the LPC2138 watchdog with generate an interrupt and may cause a reset depending on the state of WDMOD:WDRESET bit. I can see the interrupt being useful during debugging when the reset is disabled, but does it serve any purpose when the reset is enabled? Would the ISR even get serviced if the watchdog times out and a reset is forced?
2005-01-27 by Rick Collins
--- In lpc2000@yahoogroups.com, "tah2k" <tah2k@y...> wrote: > > When enabled and timed out, the LPC2138 watchdog with generate an > interrupt and may cause a reset depending on the state of > WDMOD:WDRESET bit. > > I can see the interrupt being useful during debugging when the reset > is disabled, but does it serve any purpose when the reset is > enabled? Would the ISR even get serviced if the watchdog times out > and a reset is forced? I think the idea is that you can either reset the chip, or you can use the interrupt. I don't know why you would use the interrupt instead of the reset, but I have seen PC based embedded systems that use a normal timer interrupt as a watchdog when no watchdog hardware was available. It was more of a way to detect that one of the tasks was not responding.
2005-01-27 by lpc2100_fan
--- In lpc2000@yahoogroups.com, "Rick Collins" <gnuarm@a...> wrote: > > --- In lpc2000@yahoogroups.com, "tah2k" <tah2k@y...> wrote: > > > > When enabled and timed out, the LPC2138 watchdog with generate an > > interrupt and may cause a reset depending on the state of > > WDMOD:WDRESET bit. > > > > I can see the interrupt being useful during debugging when the reset > > is disabled, but does it serve any purpose when the reset is > > enabled? Would the ISR even get serviced if the watchdog times out > > and a reset is forced? > > I think the idea is that you can either reset the chip, or you can > use the interrupt. I don't know why you would use the interrupt > instead of the reset, but I have seen PC based embedded systems that > use a normal timer interrupt as a watchdog when no watchdog hardware > was available. It was more of a way to detect that one of the tasks > was not responding. Hi, using the watchdog with interrupt has two options, you use it as a periodic timer interrupt or for debugging, if it ever hits you know that your application is not feeding the watchdog frequently enough. For the reset, this should be default in a running and debugged application. The idea behind the watchdog is that e.g. your main loop services the watchdog and if your program execution becomes undefined the program will not longer return to the lowest priority main loop. The only way to get out is probably a reset. This is what the WDT will do. hth Bob
2006-03-16 by rekerj@duerkopp-adler.com
Hi, how can I use the watchdog as a periodic timer? >using the watchdog with interrupt has two options, you use it as a >periodic timer interrupt or for debugging,... The information i've found in the manual is: "The Watchdog Interrupt Flag is set when the watchdog times out. This flag is cleared when any reset occurs." Due to this it isn't possible to clear the Watchdog Interrupt Flag by software. But when I can't clear this flag, I can handle this interrupt only one time and that wouldn't be sense of a periodic timer. Juergen
2006-03-16 by Jayasooriah
Hi Juergen, You cannot use the watchdog as a periodic timer interrupt because on watchdog interrupt the CPU is reset almost equivalent to an external reset. Jaya --- In lpc2000@yahoogroups.com, rekerj@... wrote: > > Hi, > > how can I use the watchdog as a periodic timer? > > >using the watchdog with interrupt has two options, you use it as a > >periodic timer interrupt or for debugging,... > > The information i've found in the manual is: > "The Watchdog Interrupt Flag is set when the watchdog times out. This flag is cleared when any reset occurs." > > Due to this it isn't possible to clear the Watchdog Interrupt Flag by software. But when I can't clear this flag, I can handle this interrupt only one time and that wouldn't be sense of a periodic timer. > > Juergen Send instant messages to your online friends http://au.messenger.yahoo.com
2006-03-16 by Guillermo Prandi
Jaya: the LPC allows you to choose between reset and interrupt when Watchdog is triggered by means of the WDMOD register. If you set WDMOD to 0x01, you'll get a normal IRQ through the VIC when the watchdog is triggered; if you set it to 0x03, you will get a reset (which is similar to a hardware reset). Guille --- In lpc2000@yahoogroups.com, Jayasooriah <jayasooriah@...> wrote: > > Hi Juergen, > > You cannot use the watchdog as a periodic timer interrupt because on > watchdog interrupt the CPU is reset almost equivalent to an external reset. > > Jaya > > --- In lpc2000@yahoogroups.com, rekerj@ wrote: > > > > Hi, > > > > how can I use the watchdog as a periodic timer? > > > > >using the watchdog with interrupt has two options, you use it as a > > >periodic timer interrupt or for debugging,... > > > > The information i've found in the manual is: > > "The Watchdog Interrupt Flag is set when the watchdog times out. This > flag is cleared when any reset occurs." > > > > Due to this it isn't possible to clear the Watchdog Interrupt Flag by > software. But when I can't clear this flag, I can handle this interrupt > only one time and that wouldn't be sense of a periodic timer. > > > > Juergen > > Send instant messages to your online friends http://au.messenger.yahoo.com >
2006-03-16 by K B Shah-lascaux
Hi, Philips Semiconductors Preliminary User Manual LPC2119/2129/2194/2292/2294 ARM-based Microcontroller Watchdog Mode Register (WDMOD - 0xE0000000) The WDMOD register controls the operation of the Watchdog as per the combination of WDEN and RESET bits. WDEN WDRESET 0 X Debug/Operate without the Watchdog running 1 0 Debug with the Watchdog interrupt but no WDRESET 1 1 Operate with the Watchdog interrupt and WDRESET Once the WDEN and/or WDRESET bits are set they can not be cleared by software. Both flags are cleared by an external reset or a Watchdog timer underflow.
----- Original Message -----
From: Guillermo Prandi
To: lpc2000@yahoogroups.com
Sent: Thursday, March 16, 2006 12:36 PM
Subject: [lpc2000] Re: LPC2138 Watchdog
Jaya: the LPC allows you to choose between reset and interrupt when
Watchdog is triggered by means of the WDMOD register. If you set
WDMOD to 0x01, you'll get a normal IRQ through the VIC when the
watchdog is triggered; if you set it to 0x03, you will get a reset
(which is similar to a hardware reset).
Guille
--- In lpc2000@yahoogroups.com, Jayasooriah <jayasooriah@...> wrote:
>
> Hi Juergen,
>
> You cannot use the watchdog as a periodic timer interrupt because
on
> watchdog interrupt the CPU is reset almost equivalent to an
external reset.
>
> Jaya
>
> --- In lpc2000@yahoogroups.com, rekerj@ wrote:
> >
> > Hi,
> >
> > how can I use the watchdog as a periodic timer?
> >
> > >using the watchdog with interrupt has two options, you use it
as a
> > >periodic timer interrupt or for debugging,...
> >
> > The information i've found in the manual is:
> > "The Watchdog Interrupt Flag is set when the watchdog times out.
This
> flag is cleared when any reset occurs."
> >
> > Due to this it isn't possible to clear the Watchdog Interrupt
Flag by
> software. But when I can't clear this flag, I can handle this
interrupt
> only one time and that wouldn't be sense of a periodic timer.
> >
> > Juergen
>
> Send instant messages to your online friends
http://au.messenger.yahoo.com
>
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[Non-text portions of this message have been removed]2006-03-16 by Jayasooriah
Thanks Guile and Shah-lascaux. Yes the watchdog on LPC has features that allows it to be used just as an interval timer. There is your answer Jurgen. >Message: 5 > Date: Thu, 16 Mar 2006 13:29:30 -0500 > From: "K B Shah-lascaux" <kbshah@...> >Subject: Re: Re: LPC2138 Watchdog > >Hi, >Philips Semiconductors Preliminary User Manual > >LPC2119/2129/2194/2292/2294 ARM-based Microcontroller > >Watchdog Mode Register (WDMOD - 0xE0000000) > >The WDMOD register controls the operation of the Watchdog as per the >combination of WDEN and RESET bits. > >WDEN WDRESET > >0 X Debug/Operate without the Watchdog running > >1 0 Debug with the Watchdog interrupt but no WDRESET > >1 1 Operate with the Watchdog interrupt and WDRESET > >Once the WDEN and/or WDRESET bits are set they can not be cleared by >software. Both flags are cleared by an external reset > >or a Watchdog timer underflow. > >----- Original Message ----- > From: Guillermo Prandi > To: lpc2000@yahoogroups.com > Sent: Thursday, March 16, 2006 12:36 PM > Subject: [lpc2000] Re: LPC2138 Watchdog > > > Jaya: the LPC allows you to choose between reset and interrupt when > Watchdog is triggered by means of the WDMOD register. If you set > WDMOD to 0x01, you'll get a normal IRQ through the VIC when the > watchdog is triggered; if you set it to 0x03, you will get a reset > (which is similar to a hardware reset). > > Guille > > --- In lpc2000@yahoogroups.com, Jayasooriah <jayasooriah@...> wrote: > > > > Hi Juergen, > > > > You cannot use the watchdog as a periodic timer interrupt because > on > > watchdog interrupt the CPU is reset almost equivalent to an > external reset. > > > > Jaya Send instant messages to your online friends http://au.messenger.yahoo.com