The 89C51 has an additional PCA interrupt.

The priority mechanism is also different compared to a normal 8051.

You can set a level in the range from 0-3.

PRIORITY SET|RESET  source , level

level can be 0,1,2 or 3.(0=lowest,3=highest)

 

The source can be :

INT0

TIMER0

INT1

TIMER1

SERIAL

TIMER2

PCA

 

PRIORITY SET INT0,3  'will set INT0 to the highest priority.

Look at a datasheet for more details.

 

The WATCHDOG can be started with the statement :

START WATCHDOG.

RESET WATCHDOG must be used in your program to reset the WD-timer.

When it reaches 16384 the chip will be reset.

The input to the WD-timer is the XTAL frequency!