Using the AT89C51RC the microvision2 target selection window says there is 1KB of on-chip XRAM available but the data sheet says 256 Bytes. I am having trouble using the XDATA and I don't know how to resolve the discrepancy. I see other chips have problems with the reset value of AUXR register and I don't know if this could be causing problems also. Is anyone using the XRAM on this chip successfully and if so is there a trick to it.
It looks like you are using an older version of the tools. In the current version the on-chip XRAM is configure with 256 bytes. For using on-chip XRAM take a look to: http://www.keil.com/support/docs/1978.htm