how can i set the real time clock (RTC) in 8052 by using c51
Uhm, The Clock address is at external data. meaning it is a xdata. You probably need to set up some kind of addressing using a Gal22V10 to put the clock at some external address. Once you do that, you do something like...
//Clear Alarm Bit Data = XBYTE[CLOCK_ADDRESS + REGISTER_C_OFFSET];