You seem to assume that there is one - and only one - possible way to connect an ad7812 to "an 89c52" (whatever that might be - see below); this is not the case!

For a start, several different manufacturers make chips with "89c52" in the part number, and even the same manufacturer may use that number with different prefixes and/or suffixes.

The general procedure you need to follow is:

1. Obtain the manufacturer's Datasheet for the ad7812;

2. Obtain the manufacturer's Datasheet for the particular "89c52" that you are using;

3. From the ad7812 Datasheet, determine what signals and connections it requires;

4. From the "89c52" Datasheet, determine what connections and resources it has available to fulfil those requirements (and which of them are available, considering the other requirements of your system).

For help in that process, check the ad7812 manufacturer's website for other supporting materials such as Application Notes, Examples, Reference Designs, etc, etc...

Note: If at all possible, obtain the genuine, original datasheets from the Manufacturer's website - do not rely upon 3rd-party datasheet "archives" or collections unless you really have to!