Using xdata memory and writing to flash/EE data with ECON/EDATA

When enabling the internal xdata memory (XRAMEN EQ 1 in START_AD.A51), writing to the flash/EE data memory fails with error code 15 in ECON in the code below.

If XRAMEN is set to 0, xdata does not work, but writing to the flash/EE data memory works.

What do I have to do so I can use the internal xdata memory and write to the flash/EE data memory?

int SpWrite(int adress, char b1, char b2, char b3, char b4)
{
  int high = adresse >> 8;
  int low = adresse & 0xFF;
  int ret;

  EADRH = high;
  EADRL = low;
  EDATA1 = b1;
  EDATA2 = b2;
  EDATA3 = b3;
  EDATA4 = b4;
  ECON=5;		// Erase
  ECON=2;		// write
  ECON=4;		// verify
  ret = ECON;
  return ret;
}

This code works and returns 0 (no error) whenever XRAMEN is set to 0. As soon as I set XRAMEN to 1, I always get a return code 15.

We are using Win2000 SP3, Keil CA51 and ADuC831.