I used AT89S8253 and I activated the watchdog with desired configuration :
- 64 ms prescaler.
- hardware mode select for the WDT.
- RST pin is driven high after WDT times out and the entire board is reset.

Hence, I wrote on program like this:

...
orl wdtcon,#01000000B
orl wdtcon,#00000100B
anl wdtcon,#01000101B
mov wdtrst,#1EH
mov wdtrst,#0E1H
jnb lock,authorized
sjmp$
authorized: setb ea
setb tr0
setb tr1
...

The meaning of the program is :
If 'lock' flag bit was not set, then the program would be continued. If 'lock' was set then the program would be hung.

The problem occured when I was trying to hang the program ('lock' flag was forced to '1'). If the program above was correct, the RST pin should be driven to '1' after WDT times out but it won't happened. RST pin was unchanged ('0') and uC could not reset entire board.

Any suggestions for me? Thank you very much.

Regards,
-EKA-