spirax345
Without looking at a schematic I can only guess at what you are working with. Serial EEPROMs are not intended to contain instructions which the processor executes directly. In order to use a serial EEPROM for non-volitile data storage you need to have some code in the 80C552's code space.
A 27C512 contains 64K bytes of memory space. This is all the code space the 8051 architecture allows. If this is an existing, working design, then I expect that the 27C512's chip select is grounded, and it's OE-bar is connected to PSEN-bar. PSEN stands for Program Store Enable. PSEN is active for ALL instruction fetchs from External Memory, AND for all data READS using the MOVC instruction. The MOVC instruction can only READ from External Memory, it cannot write.
The RAM on the other hand connects to the very same address and data lines as the 27C512. Its chip select is also permanently grounded. BUT its OE-bar is connect to RD-bar(Port 3.7) and its WE-bar is connected to WE-bar(Port 3.6). These two Port 3 signals are active for all DATA READS and DATA WRITES using the instruction MOVX. The MOVX instruction can read and write to a completely different address space than the one occupied by the instructions.
Hope this helps