variable at fixed memory address

Hello,
how can I tell the compiler / linker that a variable (here int16_t iAverageValues [16]) is always at the same address? I need it for the XCP-Protocol. I don't want to update the addressmapping after building a new softwareversion.
I've tried following thinks, but with no success:
int16_t iAverageValues [16] __attribute__((at(0x2000FFC0)));
or
int16_t iAverageValues [16] __attribute__ ((section (XCP_DATA)));
an modify the linker script with something like this
XCP_Data(!RX) : ORIGIN = 0x200FFC0, LENGTH = 0x20

Thanks
Markus