how to access ERAM in AT89LP51RD2

How to access ERAM(2 KB on chip memory) in AT89lp51rd2?
I have added following code to STARTUP.A51 file.

XDATALEN EQU 7FFH
ANL AUXR1,#NOT 02H ; AUXR1/Bit 1 (clear to 0 to enable on-chip XRAM).

if I add following lines, program hang.

xdata char *ptr;

for(ptr=0;ptr<0x300;ptr++)
{
  *ptr=0;
}
//---clearing 768 bytes of ERAM