Access to register

I'm using the soft-core Cortex-M0,keil uvision 5,vivado 14.4 i interfaced an accelerator with my arm architecture,
when i do this,in vivado simulator , the HWDATA=129! , why?

void kalman(int a);

int main(void) {
volatile signed int *rega = (volatile signed int *) 0x59000000; static int b; b =9; *rega=5; kalman(b);

}

void kalman(int a){

volatile signed int *rega = (volatile signed int *) 0x59000004; *rega=a;

}