The AT89S8252 has a built in watchdog timer.
A watchdog timer is a timer that will reset the uP when it reaches a certain value.
So during program execution this WD-timer must be reset before it exceeds its maximum value.
This is used to be sure a program is running correct.
When a program crashes or sits in an endless loop it will not reset the WD-timer so an automatic reset will occur resulting in a restart.
START WATCHDOG will start the watchdog timer.
STOP WATCHDOG will stop the watchdog timer.
RESET WATCHDOG will reset the watchdog timer.
See also
Example
'-----------------------------------------------------
' (c) 1998 MCS Electronics
' WATCHD.BAS demonstrates the AT89S8252 watchdog timer
' select 89s8252.dat !!!
'-----------------------------------------------------
Config Watchdog = 2048 'reset after 2048 mSec
Start Watchdog 'start the watchdog timer
Dim I As Word
For I = 1 To 10000
Print I 'print value
' Reset Watchdog
'you will notice that the for next doesnt finish because of the reset
'when you unmark the RESET WATCHDOG statement it will finish because the
'wd-timer is reset before it reaches 2048 msec
Next
End