Nios readdata problem

Hi, I have a strange problem about reading the readdata.

I designed a user logic and wrote a C code corresponding to it.

I hope use this circuit to do caculations twice. And I get right result at the fisrt time reading the readdata signal.

However, when I want to get the second result, the result is still the value which is gotten at the first time.

Therefore, I use the Modelsim to check the corresponding signal. I find that the chipselect signal just arise once.

That means the chipselect signal does not arise at the second time when I want to retrieve the second result.

Does anyone have the same experience ?? Following is my C code :

# include<stdio.h># include "excalibur.h"

float x,y,z,result;

float a,b,c,result_1;

float cmp = 4.0;

int main(void)

{

float *p;

printf("========startCompute======== \n");

x = 1.5; // I have three float-point operands

y = 2.0;

z = 0.5;

printf("x is %f, y is %f, z is %f\n", x,y,z);

p = 0x920800; // the starting address of the user logic

*p = x; // write the first operand to the first register address

*(p+1) = y; // write the second operand to the first register address

*(p+2) = z; // write the third operand to the first register address

*(p+3) = 2.0; // use to control the start signal. that means when write *(p+3), the circuit starts calculation

while(((*(p+3))&& cmp)== 0)

{

printf("inwhile \n");

}

result = *(p+4); // get the first result from the *(p+4) address. It is right.

printf("result is = %f\n" ,result);

//==========================================================

*p = 0.0; // Clear all operands

*(p+1) = 0.0;

*(p+2) = 0.0;

*(p+3) = 0.0;

//==========================================================

printf("===start second computation!!\n");

a = 1.2; // the three new operands

b = 2.1;

c = 3.4;

printf("a is %f, b is %f, c is %f\n", a,b,c);

*p = a;

*(p+1) = b;

*(p+2) = c;

*(p+3) = 2.0;

while(((*(p+3))&& cmp)== 0)

{

printf("inwhile \n");

}

result_1 = *(p+4); // get the result from *(p+4) address. But the result is still the same with the fisrt one. Why????????????

printf("result_1 is = %f\n" ,result_1);

return 0;

}

Does anybody can solve this problem ??

Thanks a lot.