#include <reg52.h>
sbit PWMOUT = P0^0;
sbit ADDR0 = P1^0;
sbit ADDR1 = P1^1;
sbit ADDR2 = P1^2;
sbit ADDR3 = P1^3;
sbit ENLED = P1^4;
unsigned long PeriodCnt = 0; //PWM周期計數值
unsigned char HighRH = 0; //高電平重載值的高字節
unsigned char HighRL = 0; //高電平重載值的低字節
unsigned char LowRH = 0; //低電平重載值的高字節
unsigned char LowRL = 0; //低電平重載值的低字節
unsigned char T1RH = 0; //T1重載值的高字節
unsigned char T1RL = 0; //T1重載值的低字節
void ConfigTimer1(unsigned int ms);
void ConfigPWM(unsigned int fr, unsigned char dc);
void main()
{
EA = 1; //開總中斷
ENLED = 0; //使能獨立LED
ADDR3 = 1;
ADDR2 = 1;
ADDR1 = 1;
ADDR0 = 0;
ConfigPWM(100, 10); //配置并啟動PWM
ConfigTimer1(50); //用T1定時調整占空比
while (1);
}
/* 配置并啟動T1，ms-定時時間 */
void ConfigTimer1(unsigned int ms)
{
unsigned long tmp; //臨時變量
tmp = 11059200 / 12; //定時器計數頻率
tmp = (tmp * ms) / 1000; //計算所需的計數值
tmp = 65536 - tmp; //計算定時器重載值
tmp = tmp + 12; //補償中斷響應延時造成的誤差
T1RH = (unsigned char)(tmp>>8); //定時器重載值拆分為高低字節
T1RL = (unsigned char)tmp;
TMOD &= 0x0F; //清零T1的控制位
TMOD |= 0x10; //配置T1為模式1
TH1 = T1RH; //加載T1重載值
TL1 = T1RL;
ET1 = 1; //使能T1中斷
TR1 = 1; //啟動T1
}
/* 配置并啟動PWM，fr-頻率，dc-占空比 */
void ConfigPWM(unsigned int fr, unsigned char dc)
{
unsigned int high, low;
PeriodCnt = (11059200/12) / fr; //計算一個周期所需的計數值
high = (PeriodCnt*dc) / 100; //計算高電平所需的計數值
low = PeriodCnt - high; //計算低電平所需的計數值
high = 65536 - high + 12; //計算高電平的定時器重載值并補償中斷延時
low = 65536 - low + 12; //計算低電平的定時器重載值并補償中斷延時
HighRH = (unsigned char)(high>>8); //高電平重載值拆分為高低字節
HighRL = (unsigned char)high;
LowRH = (unsigned char)(low>>8); //低電平重載值拆分為高低字節
LowRL = (unsigned char)low;
TMOD &= 0xF0; //清零T0的控制位
TMOD |= 0x01; //配置T0為模式1
TH0 = HighRH; //加載T0重載值
TL0 = HighRL;
ET0 = 1; //使能T0中斷
TR0 = 1; //啟動T0
PWMOUT = 1; //輸出高電平
}
/* 占空比調整函數，頻率不變只調整占空比 */
void AdjustDutyCycle(unsigned char dc)
{
unsigned int high, low;
high = (PeriodCnt*dc) / 100; //計算高電平所需的計數值
low = PeriodCnt - high; //計算低電平所需的計數值
high = 65536 - high + 12; //計算高電平的定時器重載值并補償中斷延時
low = 65536 - low + 12; //計算低電平的定時器重載值并補償中斷延時
HighRH = (unsigned char)(high>>8); //高電平重載值拆分為高低字節
HighRL = (unsigned char)high;
LowRH = (unsigned char)(low>>8); //低電平重載值拆分為高低字節
LowRL = (unsigned char)low;
}
/* T0中斷服務函數，產生PWM輸出 */
void InterruptTimer0() interrupt 1
{
if (PWMOUT == 1) //當前輸出為高電平時，裝載低電平值并輸出低電平
{
TH0 = LowRH;
TL0 = LowRL;
PWMOUT = 0;
}
else //當前輸出為低電平時，裝載高電平值并輸出高電平
{
TH0 = HighRH;
TL0 = HighRL;
PWMOUT = 1;
}
}
/* T1中斷服務函數，定時動態調整占空比 */
void InterruptTimer1() interrupt 3
{
static bit dir = 0;
static unsigned char index = 0;
unsigned char code table[13] = { //占空比調整表
5, 18, 30, 41, 51, 60, 68, 75, 81, 86, 90, 93, 95
};
TH1 = T1RH; //重新加載T1重載值
TL1 = T1RL;
AdjustDutyCycle(table[index]); //調整PWM的占空比
if (dir == 0) //逐步增大占空比
{
index++;
if (index >= 12)
{
dir = 1;
}
}
else //逐步減小占空比
{
index--;
if (index == 0)
{
dir = 0;
}
}
}
