#include<reg52.h>
sbit PIN_RXD = P3^0;
sbit PIN_TXD = P3^1;
bit RxdorTxd = 0;
bit RxdEnd = 0;
bit TxdEnd = 0;
unsigned char RxdBuf = 0;
unsigned char TxdBuf = 0;
void ConfigUART(unsigned int baud);
void StartTXD(unsigned char dat);
void StartRXD();
void main()
{
EA = 1;
ConfigUART(9600);
while(1)
{
while(PIN_RXD);
StartRXD();
while(!RxdEnd);
StartTXD(RxdBuf+1);
while(!TxdEnd);
}
}
void ConfigUART(unsigned int baud)
{
TMOD &= 0xF0;
TMOD |= 0x02;
TH0 = 256 - (11059200/12)/baud;
}
void StartRXD()
{
TL0 = 256 - ((256 - TH0)>>1);
ET0 = 1;
TR0 = 1;
RxdEnd = 0;
RxdorTxd = 0;
}
void StartTXD(unsigned char dat)
{
TxdBuf = dat;
TL0 = TH0;
ET0 = 1;
TR0 = 1;
PIN_TXD = 0;
TxdEnd = 0;
RxdorTxd = 1;
}
void timer0() interrupt 1
{
static unsigned char cnt = 0;
if(RxdorTxd)
{
cnt++;
if(cnt <= 8)
{
PIN_TXD = TxdBuf & 0x01;
TxdBuf >>= 1;
}
else if(cnt == 9)
{
PIN_TXD = 1;
}
else
{
cnt = 0;
TR0 = 0;
TxdEnd = 1;
}
}
else
{
if(cnt == 0)
{
if(!PIN_RXD)
{
RxdBuf = 0;
cnt++;
}
else
{
TR0 = 0;
}
}
else if(cnt <= 8)
{
RxdBuf >>= 1;
if(PIN_RXD)
{
RxdBuf |= 0x80;
}
cnt++;
}
else
{
cnt = 0;
TR0 = 0;
if(PIN_RXD)
RxdEnd = 1;
}
}
}