You have to define all registers as pointers at tehe begining of the C code, for exameple:
#define SCRRX (int*)0xFFD4 //; SSI Receive Control Register
#define SCRTX (int*)0xFFD3 //; SSI Transmit Control Register
#define SCR2 (int*)0xFFD2 //; SSI Control Register 2
#define STX (int*)0xFFD0 //; SSI Transmit Register
#define SRX (int*)0xFFD0 //; SSI Receive Register
#define SSR (int*)0xFFD1 //; SSI status register
And to read or write the register you have to refer to itself like:
*SCRRX = 0x6F04; //PSR=0, WL=3, DC=15, PM=4
*SCRTX = 0x6F04; // PSR=0, WL=3, DC=15, PM=4
hope it may help...