"现在急死了"

wow. I thought only a girly man would get killed by a simple program

here is software-uart, in C.

======uart-sw==================

void usart_putch(unsigned char ch)
{
        unsigned char bitcount=1+8+1;                        //start bit, 8 data bits, 1 stop bit
        //each
        //RB4=0;
        IO_CLR(USART_PORT, USART_Tx);                //drive tx pin low - usart start condition
        do {
                usart_delay_tx_bit();                                //delay some time
                if (ch & 0x01) IO_SET(USART_PORT, USART_Tx);        //send a 1
                else IO_CLR(USART_PORT, USART_Tx);                //otherwise, send a 0
                ch=(ch>>1) | 0x80;                                //shift out the next bit
        } while (--bitcount);
        //NOP();
}
===========end=============


hardware uart is even simpler:

====uart-hw===========

void usart_putch(unsigned char ch)
{
        //Wait for TXREG Buffer to become available
        //while(!TXIF);                        //wait for prior transmission to finish
        USART_WAIT(TXIF);

        //Write data
        TXREG=ch;                                //load up the tx register

        //while(!TRMT);                        //wait for the transmission to finish
                                                        //don't use txif as this is not back-to-back transmission
}
============end================