Re: [bascom] ATMega8 Watchdog Question

["Richard Prosser" <rhprosser@gmail.com>]

Ian,
I think the watchdog timeout will always cause a reset - so you need
to do the timeout check at the start of the code. The wdrf flag is
reset by a normal reset and set by a timeout reaset - (as you have
determined) so you can create a jump from there to the powerdown
routine.

You'll just have to do the test before you start configuring
peripherals and writing to ram - so you'll have to figure out a way of
bypassing the normal BASCOM startup routines.
$noramclear and/or  $noinit may be be useful. but you'll then have to
write your own initialisation code.

That's my take on it anyway - the manual doesn't seem to spell it out
clearly but it's in agreement with your output messages (Partially
corrupted by premature shutdown?)

Also, Your INT0 interrupt handler terminates with a Retfi assembly
instruction wheras it should terminate with a BASCOM  "Return". There
may be no difference in this case but the "Return" instruction will
generate the context handling code required under normal conditions. I
can't see it causing this wakeup problem but it would create problems
later on when you're handling the INT0 interrupt.

Richard P


On 19/05/06, ian dobson <i.dobson@planet-ian.com> wrote:
> Hi,
>
> The watchdog interrupt causes a reset. It's normally used to catch program
> crashes.
>
> Regards
> Ian Dobson
>
> Home of the Atmel based UDP mobile web cam http://www.planet-ian.com
> All mails scanned with av-filter.pl (F-Prot / perl)
>
> ----- Original Message -----
> From: Fanie Terblanche
> To: Bascom
> Sent: Thursday, May 18, 2006 5:22 PM
> Subject: [bascom] ATMega8 Watchdog Question
>
> Hi All,
>
> I have a question about the WDT. If the program wakes up from the WDT it
> restarts the program, and i just want to reset the WDT and go back to sleep
> if it was not INT0 that woke me up.
>
> Thanks in advance
> Fanie.
>
> This is the output i get
> -------------------------------------
> START
> Before Sleep
> WDT
> START
> Before Sleep
> WDT
> START
> This is the test program used.
> --------------------------------------
> $regfile = "m8def.dat"
> $crystal = 8000000
> $baud = 9600
>
> Config Int0 = Falling
> On Int0 Measurepulse
> Config Watchdog = 2048
> 'reset after 2048 mSec
> Start Watchdog
> 'start the watchdog timer
> Reset Watchdog
> Enable Interrupts
> Enable Int0
>
> Print "START"
>
> Do
>   Gosub Shutdownpower
> ' The following code will only be executed if INT0 woke me up
>   Reset Watchdog
>   Print "INT 0 woke me up !!!!"
> Loop
>
> Shutdownpower:
>   Print "Before Sleep"
> __wdtr:
>   Print "Reset WDT"
>   Reset Watchdog
>   cbi MCUCSR,WDRF
> 'Clear the MCUCSR Flags
>   cbi MCUCSR,BORF
> 'Clear the MCUCSR Flags
>   cbi MCUCSR,EXTRF
> 'Clear the MCUCSR Flags
>   cbi MCUCSR,PORF
> 'Clear the MCUCSR Flags
>   Powerdown
> 'Goto Sleep
>   sbic MCUCSR,WDRF
> 'Check if the WDT woke us up
>   jmp __wdtr
>   Print "NOT WDT"
> 'NOT the WDT
>   cbi MCUCSR,WDRF
>   cbi MCUCSR,BORF
>   cbi MCUCSR,EXTRF
>   cbi MCUCSR,PORF
>   Print "After Sleep"
> Return
>
> Measurepulse:
>   Print "INT 0"
>   Reset Watchdog
> Reti
>
>
>
>
> START
> Before Sleep
> WDT
> START
> Before Sleep
> WDT
> START