DSP中的综合交通灯演示实例的算法，基于TI公司的5509这款芯片
#include "scancode.h"
#define SPSA0 *(unsigned int *)0x38
#define SPSD0 *(unsigned int *)0x39
#define REGISTERCLKMD (*(unsigned int *)0x58)
#define TIM  *(int *)0x24
#define PRD     *(int *)0x25
#define TCR  *(int *)0x26
#define IMR  *(int *)0x0
#define IFR  *(int *)0x1  
#define PMST *(int *)0x1d
#define nStatusNSGreenEWRed 160
#define nStatusNSFlashEWRed 184
#define nStatusNSYellowEWRed 200
#define nStatusNSRedEWYellow 216
#define nStatusNSRedEWGreen 376
#define nStatusNSRedEWFlash 400
#define nStatusNSRedEWYellow1 416
#define nStatusNSYellowEWRed1 432
#define nTotalTime 448
#define nStatusHold 160
#define statusNSGreenEWRed 0
#define statusNSFlashEWRed 1
#define statusNSYellowEWRed 2
#define statusNSRedEWYellow 3
#define statusNSRedEWGreen 4
#define statusNSRedEWFlash 5
#define statusHold 6

ioport unsigned int port3004;
ioport unsigned int port8000;
ioport unsigned char port8001;
ioport unsigned char port8002;
ioport unsigned int port8005;
ioport unsigned int port8007;
void InitDSP();
void InitTimer();
void InitICETEKCTR();
void interrupt time(void);
void interrupt xint2(void); // XINT2中断服务程序
void SetLEDArray(int nNumber);  // 修改显示内容
void RefreshLEDArray();   // 刷新显示
void EndICETEKCTR();
unsigned int uWork,nTimeCount;
unsigned int uLightStatusEW,uLightStatusSN;
unsigned int bHold;
unsigned char ledbuf[8],ledx[8];
unsigned char led[40]=
{
0x7E,0x81,0x81,0x7E,0x00,0x02,0xFF,0x00,
0xE2,0x91,0x91,0x8E,0x42,0x89,0x89,0x76,
0x38,0x24,0x22,0xFF,0x4F,0x89,0x89,0x71,
0x7E,0x89,0x89,0x72,0x01,0xF1,0x09,0x07,
0x76,0x89,0x89,0x76,0x4E,0x91,0x91,0x7E
};
main()
{
int nWork1,nWork2,nWork3,nWork4;
int nNowStatus,nOldStatus,nOldTimeCount,nSaveTimeCount,nSaveStatus;
unsigned int nScanCode;

nTimeCount=0; bHold=0;
uLightStatusEW=uLightStatusSN=0;
nNowStatus=0; nOldStatus=1; nOldTimeCount=0;
InitDSP();   // 初始化DSP，设置运行速度
InitICETEKCTR(); // 初始化显示/控制模块
InitTimer();  // 设置定时器中断
// 根据计时器计数切换状态
// 根据状态设置计数和交通灯状态
while ( 1 )   
{
  if ( bHold && nNowStatus==statusHold )
  {
   if ( nTimeCount>=nStatusHold )
   {
    nNowStatus=nSaveStatus;
    nTimeCount=nSaveTimeCount;
    bHold=0;
   }
  }
  else if ( nTimeCount<nStatusNSGreenEWRed ) nNowStatus=statusNSGreenEWRed;
  else if ( nTimeCount<nStatusNSFlashEWRed ) nNowStatus=statusNSFlashEWRed;
  else if ( nTimeCount<nStatusNSYellowEWRed ) nNowStatus=statusNSYellowEWRed;
  else if ( nTimeCount<nStatusNSRedEWYellow ) nNowStatus=statusNSRedEWYellow;
  else if ( nTimeCount<nStatusNSRedEWGreen ) nNowStatus=statusNSRedEWGreen;
  else if ( nTimeCount<nStatusNSRedEWFlash ) nNowStatus=statusNSRedEWFlash;
  else if ( nTimeCount<nStatusNSRedEWYellow1 ) nNowStatus=statusNSRedEWYellow;
  else if ( nTimeCount<nStatusNSYellowEWRed1 ) nNowStatus=statusNSYellowEWRed;
  if ( nNowStatus==nOldStatus )
  {
   switch ( nNowStatus )
   {
    case statusNSFlashEWRed:
     nWork1=nTimeCount-nStatusNSGreenEWRed;
     nWork2=nStatusNSYellowEWRed-nStatusNSFlashEWRed;
     nWork3=nWork2/3;
     nWork4=nWork3/2;
     if ( nWork1>=0 && nWork2>0 && nWork3>0 && nWork4>0 )
      uLightStatusSN=( (nWork1%nWork3)<=nWork4 )?(0x49):(0x40);
     break;
    case statusNSRedEWFlash:
     nWork1=nTimeCount-nStatusNSRedEWGreen;
     nWork2=nStatusNSRedEWYellow1-nStatusNSRedEWFlash;
     nWork3=nWork2/3;
     nWork4=nWork3/2;
     if ( nWork1>=0 && nWork2>0 && nWork3>0 && nWork4>0 )
      uLightStatusEW=( (nWork1%nWork3)<=nWork4 )?(0x09):(0x00);
     break;
    case statusNSGreenEWRed:
     nWork1=nStatusNSGreenEWRed/20;
     if ( nWork1>0 )
     {
      nWork2=20-nTimeCount/nWork1;
      if ( bHold )
      {
       if ( nWork2>10 )
       {
        nTimeCount=nWork1*10;
        nWork2=10;
       }
      }
      if ( nOldTimeCount!=nWork2 )
      {
       nOldTimeCount=nWork2;
       SetLEDArray(nWork2);
      }
     }
     break;
    case statusNSRedEWGreen:
     nWork1=(nStatusNSRedEWGreen-nStatusNSRedEWYellow)/20;
     if ( nWork1>0 )
     {
      nWork2=20-(nTimeCount-nStatusNSRedEWYellow)/nWork1;
      if ( bHold )
      {
       if ( nWork2>10 )
       {
        nTimeCount=nStatusNSRedEWYellow+nWork1*10;
        nWork2=10;
       }
      }
      if ( nOldTimeCount!=nWork2 )
      {
       nOldTimeCount=nWork2;
       SetLEDArray(nWork2);
      }
     }
     break;
    case statusHold:
     nWork1=nStatusHold/20;
     if ( nWork1>0 )
     {
      nWork2=20-nTimeCount/nWork1;
      if ( nOldTimeCount!=nWork2 )
      {
       nOldTimeCount=nWork2;
       SetLEDArray(nWork2);
      }
     }
     break;
   }
  }
  else
  {
   if ( bHold )
   {
    nSaveStatus=nNowStatus;
    nSaveTimeCount=nTimeCount;
    nNowStatus=statusHold;
    nTimeCount=0;
    if ( nSaveStatus==statusNSFlashEWRed || nSaveStatus==statusNSYellowEWRed )
    {
     nSaveStatus=statusNSRedEWGreen;
     nSaveTimeCount=nStatusNSRedEWYellow;
    }
    else if ( nSaveStatus==statusNSRedEWFlash || nSaveStatus==statusNSRedEWYellow )
    {
     nSaveStatus=statusNSGreenEWRed;
     nSaveTimeCount=0;
    }
   }
   nOldStatus=nNowStatus;
   switch ( nNowStatus )
   {
    case statusNSGreenEWRed:
     uLightStatusEW=0x24; uLightStatusSN=0x49;
     SetLEDArray(20);
     break;
    case statusNSFlashEWRed:
     uLightStatusEW=0x24; uLightStatusSN=0x49;
     SetLEDArray(0);
     break;
    case statusNSYellowEWRed:
     uLightStatusEW=0x24; uLightStatusSN=0x52;
     SetLEDArray(20);
     break;
    case statusNSRedEWYellow:
     uLightStatusEW=0x12; uLightStatusSN=0x64;
     SetLEDArray(20);
     break;
    case statusNSRedEWGreen:
     uLightStatusEW=0x09; uLightStatusSN=0x64;
     SetLEDArray(20);
     break;
    case statusNSRedEWFlash:
     uLightStatusEW=0x09; uLightStatusSN=0x64;
     SetLEDArray(0);
     break;
    case statusHold:
     uLightStatusEW=0x24; uLightStatusSN=0x64;
     SetLEDArray(20);
     break;
   }
  }
  port8007=uLightStatusEW; port8007=uLightStatusSN; // 设置交通灯状态
  RefreshLEDArray(); // 刷新发光二极管显示
  nScanCode=port8001; // 读键盘扫描码
  nScanCode&=0x0ff;
  if ( nScanCode==SCANCODE_Enter ) break;
}
EndICETEKCTR();
exit(0);
}
// 定时器中断服务程进行时钟计数
void interrupt time(void)
{
nTimeCount++;
nTimeCount%=nTotalTime;
}
// 设置发光二极管显示内容
void SetLEDArray(int nNumber)
{
int i,k,kk,kkk;

kkk=nNumber;
k=kkk/10*4; kk=kkk%10*4;
for ( i=0;i<4;i++ )
{
  ledbuf[7-i]=~led[k+i];
  ledbuf[3-i]=~led[kk+i];
}
}
// 将缓存中点阵送发光二极管显示
void RefreshLEDArray()
{
int i;
for ( i=0;i<8;i++ )
{
  port8000=ledx;
  port8005=ledbuf;
}
}
// 初始化DSP，设置运行速度=8MHz
void InitDSP()
{
REGISTERCLKMD=0; // 速度设置=8MHz
}
// 设置定时器参数、允许中断
void InitTimer()
{
unsigned int k;

asm(" ssbx INTM"); // 关中断，进行关键设置时不许打扰
// 设置通用定时器
k=PMST;   // 设置PMST寄存器
PMST =k&0xff; // 中断向量表起始地址=80H
IMR = 0x0c;  // 使能TINT
TCR = 0x41f; // 预分频系数为16
TIM = 0;  // 时钟计数器清0
PRD = 0x0f423; // 周期寄存器为0ffH
TCR = 0x42f; // 复位、启动
IFR = 0x0c;  // 清中断标志位