用单片机输出PWM程序怎么写

用51单片机

#include <reg51.h>
#include <ABSACC.H>
sbit KEY2 = P2^0;
sbit KEY3 = P2^1;
#define PWM_MAX10
unsigned char PwmValue;
unsigned char KeyScan()
{
unsigned char k;
k = '\0';
if ( KEY2 == 0 ) k = '+';
if ( KEY3 == 0 ) k = '-';
return k;
}
void T1INTSVC() interrupt 3
{
static unsigned char temp = 0;
TR1 = 0;
TH1 = 0xFF;
TL1 = 0x00;
TR1 = 1;
temp++;
if ( temp >= PWM_MAX ) temp = 0;
if ( temp <= PwmValue )
{
PWM=1;
}
else
{
PWM=0;
}
}
void Delay(unsigned int t)
{
do
{
TH0 = 0xFA;
TL0 = 0x24;
TR0 = 1;
while ( !TF0 );
TR0 = 0;
TF0 = 0;
} while ( --t != 0 );
}
void SysInit()
{
TMOD &= 0xF0;
TMOD |= 0x01;
TMOD &= 0x0F;
TMOD |= 0x10;
PwmValue = PWM_MAX / 2;
P0 = 0xff;
TH1 = 0xFF;
TL1 = 0x00;
TR1 = 1;
ET1 = 1;
EA = 1;
}
void main()
{
unsigned char k;
SysInit();
for (;;)
{
for (;;)
{
Delay(50);
k = KeyScan();
if ( k != '\0' ) break;
}
switch ( k )
{
case '+':
if ( PwmValue < PWM_MAX-1 ) PwmValue++;
break;
case '-':
if ( PwmValue > 0 ) PwmValue--;
break;
default:
break;
}
for (;;)
{
Delay(50);
if ( KeyScan() == '\0' ) break;
}
}
}