/* Program for generates a sequence cosine signal        */
/**********余弦信號產(chǎn)生程序**********************/
/*   If you use oscillograph you can see this signal      */

ioport unsigned port0bfff;

#define IOSR port0bfff
#define _COSX 0.999390827

#pragma DATA_SECTION(_COSX,"data_buf1")
float _cosx[200];
#pragma DATA_SECTION(dacdata,"data_buf2")
int dacdata[180];

void delay(void);
void main(void)
{
unsigned int i=0;
_cosx[0]=1.000;
dacdata[0]=4095;
_cosx[1]=_COSX;
dacdata[1]=_COSX*2047+2048;
  i=1;
  while(1)
   { 
     if(i++>179)
        break;
     _cosx[i]=2*_COSX*_cosx[i-1]-_cosx[i-2];
     dacdata[i]=_cosx[i]*2047+2048;
  }
  i=0;
  while(1)
   { 
     if(i>179)
       i=0;
     IOSR=dacdata[i++];
     delay();
   }
 }

void delay(void)
 {
  long int j;
  for(j=0; j<800; j++)
  asm("_nop");
 }