This thread really has nothing to do with MQX 
Firstly, you should define the varible as global i.e. outside your code body in the following format
volatile type name @0xADDRESS;
//Example copied from one of my 8 bit processors I happen to have open
volatile unsigned char __far NV_ICSTRM_FAR @0x0000FFBE;
You could always check the header files for definitions of the standard ports and copy those 
Message Edited by CarlFST60L on 2009-08-11 11:21 PM