关于单片机IO口模拟实现呼吸灯的疑问 -

/*---------------------------------------------------------------------*/
/* --- STC MCU Limited ------------------------------------------------*/
/* --- STC 1T Series MCU Demo Programme -------------------------------*/
/* 如果要在程序中使用此代码,请在程序中注明使用了STC的资料及程序 */
/*---------------------------------------------------------------------*/
/************* 功能说明 **************
使用Timer0模拟16通道PWM驱动程序。
输出为 P1.0 ~ P1.7, P2.0 ~ P2.7, 对应 PWM0 ~ PWM15.
定时器中断频率一般不要超过100KHZ, 留足够的时间给别的程序运行.
本例子使用11.0592MHZ时钟, 25K的中断频率, 250级PWM, 周期为10ms.
中断里处理的时间不超过6us, 占CPU时间大约为15%.
******************************************/
#include <reg52.h>
#define MAIN_Fosc 11059200UL //定义主时钟
#define Timer0_Rate 25000 //中断频率
typedef unsigned char u8;
typedef unsigned int u16;
typedef unsigned long u32;
sfr AUXR = 0x8E;
sfr P1M1 = 0x91; //PxM1.n,PxM0.n =00--->Standard, 01--->push-pull
sfr P1M0 = 0x92; // =10--->pure input, 11--->open drain
sfr P0M1 = 0x93;
sfr P0M0 = 0x94;
sfr P2M1 = 0x95;
sfr P2M0 = 0x96;
sfr P3M1 = 0xB1;
sfr P3M0 = 0xB2;
sfr P4M1 = 0xB3;
sfr P4M0 = 0xB4;
sfr P5M1 = 0xC9;
sfr P5M0 = 0xCA;
sfr P6M1 = 0xCB;
sfr P6M0 = 0xCC;
sfr P7M1 = 0xE1;
sfr P7M0 = 0xE2;
#define Timer0_Reload (65536UL -(MAIN_Fosc / Timer0_Rate)) //Timer 0 重装值
//************** PWM8 变量和常量以及IO口定义 ***************
//******************** 8通道8 bit 软PWM ********************
#define PWM_DUTY_MAX 250 // 0~255 PWM周期, 最大255
#define PWM_ON 1 // 定义占空比的电平, 1 或 0
#define PWM_OFF (!PWM_ON)
#define PWM_ALL_ON (0xff * PWM_ON)
u8 bdata PWM_temp1,PWM_temp2; //影射一个RAM，可位寻址，输出时同步刷新
sbit P_PWM0 = PWM_temp1^0; // 定义影射RAM每位对应的IO
sbit P_PWM1 = PWM_temp1^1;
sbit P_PWM2 = PWM_temp1^2;
sbit P_PWM3 = PWM_temp1^3;
sbit P_PWM4 = PWM_temp1^4;
sbit P_PWM5 = PWM_temp1^5;
sbit P_PWM6 = PWM_temp1^6;
sbit P_PWM7 = PWM_temp1^7;
sbit P_PWM8 = PWM_temp2^0;
sbit P_PWM9 = PWM_temp2^1;
sbit P_PWM10 = PWM_temp2^2;
sbit P_PWM11 = PWM_temp2^3;
sbit P_PWM12 = PWM_temp2^4;
sbit P_PWM13 = PWM_temp2^5;
sbit P_PWM14 = PWM_temp2^6;
sbit P_PWM15 = PWM_temp2^7;
u8 pwm_duty; //周期计数值
u8 pwm[16]; //pwm0~pwm15 为0至15路PWM的宽度值
bit B_1ms;
u8 cnt_1ms;
u8 cnt_20ms;
/**********************************************/
void main(void)
{
u8 i;
P0M0 = 0x00;
P0M1 = 0x00;
P1M0 = 0x00;
P1M1 = 0x00;
P2M0 = 0x00;
P2M1 = 0x00;
P3M0 = 0x00;
P3M1 = 0x00;
P4M0 = 0x00;
P4M1 = 0x00;
P5M0 = 0x00;
P5M1 = 0x00;
P6M0 = 0x00;
P6M1 = 0x00;
P7M0 = 0x00;
P7M1 = 0x00;
AUXR |= (1<<7); // Timer0 set as 1T mode
TMOD &= ~(1<<2); // Timer0 set as Timer
TMOD &= ~0x03; // Timer0 set as 16 bits Auto Reload
TH0 = Timer0_Reload / 256; //Timer0 Load
TL0 = Timer0_Reload % 256;
ET0 = 1; //Timer0 Interrupt Enable
PT0 = 1; //高优先级
TR0 = 1; //Timer0 Run
EA = 1; //打开总中断
cnt_1ms = Timer0_Rate / 1000; //1ms计数
cnt_20ms = 20;
for(i=0; i<16; i++) pwm[i] = i * 15 + 15; //给PWM一个初值
while(1)
{
if(B_1ms) //1ms到
{
B_1ms = 0;
if(--cnt_20ms == 0) //PWM 20ms改变一阶
{
cnt_20ms = 20;
for(i=0; i<16; i++) pwm[i]++;
}
}
}
}
/********************** Timer0 1ms中断函数 ************************/
void timer0 (void) interrupt 1
{
P1 = PWM_temp1; //影射RAM输出到实际的PWM端口
P2 = PWM_temp2;
if(++pwm_duty == PWM_DUTY_MAX) //PWM周期结束，重新开始新的周期
{
pwm_duty = 0;
PWM_temp1 = PWM_ALL_ON;
PWM_temp2 = PWM_ALL_ON;
}
ACC = pwm_duty;
if(ACC == pwm[0]) P_PWM0 = PWM_OFF; //判断PWM占空比是否结束
if(ACC == pwm[1]) P_PWM1 = PWM_OFF;
if(ACC == pwm[2]) P_PWM2 = PWM_OFF;
if(ACC == pwm[3]) P_PWM3 = PWM_OFF;
if(ACC == pwm[4]) P_PWM4 = PWM_OFF;
if(ACC == pwm[5]) P_PWM5 = PWM_OFF;
if(ACC == pwm[6]) P_PWM6 = PWM_OFF;
if(ACC == pwm[7]) P_PWM7 = PWM_OFF;
if(ACC == pwm[8]) P_PWM8 = PWM_OFF;
if(ACC == pwm[9]) P_PWM9 = PWM_OFF;
if(ACC == pwm[10]) P_PWM10 = PWM_OFF;
if(ACC == pwm[11]) P_PWM11 = PWM_OFF;
if(ACC == pwm[12]) P_PWM12 = PWM_OFF;
if(ACC == pwm[13]) P_PWM13 = PWM_OFF;
if(ACC == pwm[14]) P_PWM14 = PWM_OFF;
if(ACC == pwm[15]) P_PWM15 = PWM_OFF;
if(--cnt_1ms == 0)
{
cnt_1ms = Timer0_Rate / 1000;
B_1ms = 1; // 1ms标志
}
}

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/*---------------------------------------------------------------------*/
/* --- STC MCU Limited ------------------------------------------------*/
/* --- STC15F4K60S4 系列定时器软件模拟PWM举例-------------------------*/
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//本示例在Keil开发环境下请选择Intel的8058芯片型号进行编译
//若无特别说明,工作频率一般为11.0592MHz
#include "reg51.h"
//#define PWM6BIT 64 //6-bit PWM 周期数
#define PWM8BIT 256 //8-bit PWM 周期数
//#define PWM10BIT 1024 //10-bit PWM 周期数
//#define PWM16BIT 65536 //16-bit PWM 周期数
#define HIGHDUTY 64 //高电平周期数(占空比64/256=25%)
#define LOWDUTY (PWM8BIT-HIGHDUTY) //低电平周期数
sfr P0M1 = 0x93;
sfr P0M0 = 0x94;
sfr P1M1 = 0x91;
sfr P1M0 = 0x92;
sfr P2M1 = 0x95;
sfr P2M0 = 0x96;
sfr P3M1 = 0xb1;
sfr P3M0 = 0xb2;
sfr P4M1 = 0xb3;
sfr P4M0 = 0xb4;
sfr P5M1 = 0xC9;
sfr P5M0 = 0xCA;
sfr P6M1 = 0xCB;
sfr P6M0 = 0xCC;
sfr P7M1 = 0xE1;
sfr P7M0 = 0xE2;
sfr AUXR = 0x8e; //辅助寄存器
sfr INT_CLKO = 0x8f; //时钟输出控制寄存器
sbit T0CLKO = P3^5; //定时器0的时钟输出口
bit flag;
//定时器0中断服务程序
void tm0() interrupt 1
{
flag = !flag; //反转PWM的输出标志
if (flag)
{
TL0 = (65536-HIGHDUTY); //准备高电平的重载值
TH0 = (65536-HIGHDUTY) >> 8;
}
else
{
TL0 = (65536-LOWDUTY); //准备低电平的重载值
TH0 = (65536-LOWDUTY) >> 8;
}
}
void main()
{
P0M0 = 0x00;
P0M1 = 0x00;
P1M0 = 0x00;
P1M1 = 0x00;
P2M0 = 0x00;
P2M1 = 0x00;
P3M0 = 0x00;
P3M1 = 0x00;
P4M0 = 0x00;
P4M1 = 0x00;
P5M0 = 0x00;
P5M1 = 0x00;
P6M0 = 0x00;
P6M1 = 0x00;
P7M0 = 0x00;
P7M1 = 0x00;
AUXR = 0x80; //定时器0为1T模式
INT_CLKO = 0x01; //使能定时器0的时钟输出功能
TMOD &= 0xf0; //设置定时器0为模式0(16位自动重装载)
TL0 = (65536-LOWDUTY); //初始化定时器初值和重装值
TH0 = (65536-LOWDUTY) >> 8;
T0CLKO = 1; //初始化时钟输出脚(软PWM口)
flag = 0; //初始化标志位
TR0 = 1; //定时器0开始计时
ET0 = 1; //使能定时器0中断
EA = 1;
while (1);
}

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