ULINK2 seems to support 8051 core. Does ULINK + uVision4 configuration can be used for R8051XC core ?
Thanks
I'd consider any uC core that can not load .hex files defective
No, ULINK2 does not support the R8051XC debug interface. Please ask the manufacturer of the R8051XC IP core for a debug interface. As far as I know, they have such an interface with uVision plug-in.
BTW, then Can ISD51 or MON51 be used for R8051XC core for debugging?
ISD51 can for sure be used. ISD51 is a small 'monitor' which is linked to your application and which is then downloaded to your hardware. One serial interface is used to communiate with the PC. Mon51 could be used as well but it has quite some hardware requirements. The Monitor-51 must be installed in ROM/Flash (or downloaded with other tools if you are using a FPGA). The application is then downloaded to a v.Neumann wired RAM (accessable as XDATA and CODE). Because of this you lose quite some address space.