how to set time and date in rtc ds12c887 RAM

I am making a digital calender using ds12c887 and at89c52. I can read the time from rtc properly. But i cannot write to rtc RAM.



code fragment i am using for writing is as follows:



void rtc_set()
{
delay_ms(20); // it provide 20ms delay
PBYTE[0x0a]=0x20; //make oscilator on
PBYTE[0x0b]=0x83; // disable updates
PBYTE[0x04]=0x16; //set hours
PBYTE[0x02]=0x58; //set mins
PBYTE[0x00]=0x55; // set secs
PBYTE[0x07]=0x19; //set date
PBYTE[0x08]=0x10; //set month
PBYTE[0x09]=0x04; //set year
PBYTE[0x0b]=0x03; //enable updates
}

I do not see any issue in initialisation code. If you are able to read then you should be able to write too. After disabling updates can you do a simple write and read back, and confirm if write is a success.