The bits are in TCON which is bit addressable.
ITx is the bit where x stands for 0 or 1 depending on which interrupt you are using.

IT1 = 1 //Sets interrupt 1 to negative edge triggered

IT1 = 0 //Sets interrupt 1 to low level triggered

IT0 = 1 //Sets interrupt 0 to negative edge triggered

IT0 = 0 //Sets interrupt 1 to low level triggered


Allen