Re: LPC2138 Watchdog

Started by K B Shah-lascaux March 16, 2006
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@lpc2... 
  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@lpc2..., 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@lpc2..., 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
  > 
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An Engineer's Guide to the LPC2100 Series