Katherine,
To set the configuration bits for a PIC (including enabling the WDT), I use
the "__CONFIG"
directive in my application as follows:

 __CONFIG _CP_OFF & _XT_OSC & _WDT_ON & _PWRTE_ON

This statement sets the configuration bits as follows:
_CP_OFF   - code protect off
_XT_OSC   - standard crystal oscillator
_WDT_ON   - watch dog timer on
_PWRTE_ON - power on timer enable

These directives are bit masks that are defined in the include file for the
 processor you are using.
These are for a 16C84, so you may see some differences if you are using a
different processor.

Then in your application you need to set up the OPTION register to assign
the prescaler to the
WDT and set the prescaler rate:

     MOVLW     b'xxxx1111'    ; 'x' - not relevant for setting prescaler
assignment
     MOVWF     OPTION

These statements assign the WDT to the prescaler (bit 3 = '1'), and set the
 prescaler rate
at 128 cycles (bits 0-2 = '111').  So in your program unless you execute a
CLRWDT
instruction within 128 cycles, the WDT will reset the PIC.  So your main
application
loop may look like the following:

Main
     CLRWDT
     CALL      subroutine1
     CALL      subroutine2
     CALL      subroutine3
     GOTO      Main

If any of the subroutines "hang", the WDT will not get cleared and the PIC
will be reset.

Hope this helps,
Adam


You wrote...




cileekat@HOTMAIL.COM on 12/22/98 12:37:04 AM

Please respond to PICLIST@MITVMA.MIT.EDU

To:   PICLIST@MITVMA.MIT.EDU
cc:    (bcc: Adam Bryant/PEAK/MOORE)
Subject:  Setting the WDT of PIC16C84




Hello everybody,
I have a question on WDTs. I keep getting people telling me to enable
the WDT during programming the PIC16C84. But nobody ever specified how.
I build a programmer but didn't dare to proceed in case I spoil the PIC.
Can somebody out there please explain in as plain english terms as
possible on how to do this (Program the WDT)?
Thanks in advance.
Katherine
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