Do yourself a favour!!
Keep all this info in one thread!!! I should imagine you are using a 8051 and an AD775 to make a power meter for a school project!!!
The standard 8051/2 has no watchdog!!
If you provide all the information and what you intend to do, we will help where we can...
The ade775 outputs a pulse that can be counted... The frequency is proportional to the power used... You could gate the timer1 in the 8051 so it can count the pulses on F1 or F2 ( There are two outputs so you can drive an electro-magnetical dial!!
The datasheet shows how to determine power from the frequency!!