How to process the data from UART?

"All the ISR can usefully do is receive the data, a byte at a time, and push it into a circular buffer of adequate size. The main code will pull it out of that, and do whatever needs being done."

Absolutely.
Look at the interrupt-driven serial IO sample code on this very site.

I've used it almost straight from the can to do exactly the kind of thing you're talking about.

"All the ISR can usefully do is receive the data, a byte at a time, and push it into a circular buffer of adequate size. The main code will pull it out of that, and do whatever needs being done."

Absolutely.
Look at the interrupt-driven serial IO sample code on this very site.

I've used it almost straight from the can to do exactly the kind of thing you're talking about.

I have tried my best ,but couldn't find the code example what you said.Can you tell me which site they are?
Thanks a lot!

Click 'Support' in the blue bar across the top of this screen

Click 'Download Files'

Click 'C51 Downloas Files'

Look for "Interrupt-Driven Serial I/O"
(Hint: use your browser's 'Search' facility)

Hi all,
when the main_loop's code shown as following is running ,lots of messages in buffer couldn't be detected and lost.can you tell me how to correct it?

Serial ISR:
void serial0(void) interrupt 4
{
ES0 = 0;
if (TI0) TI0 =0;
if (RI0)
{
r_buf[r_in&0x7ff]=SBUF0;
RI0 = 0;
r_in=r_in+1;
}
ES0 = 1;
}
Main_Loop:
void main()
{
...
while(1)
{
if ((r_in-r_out)>128)
{
serial0Flag = 1;
}
if(serial0Flag==1)
{
if (r_buf[r_out&0x7ff] =='$')
{
memcpy(sHeadFlag,&r_buf[(r_out+1)&0x7ff],5);
if (memcmp(sHeadFlag,sGpgs[0],5)==0)
{
GpgsvSol(&r_buf[r_out&0x7ff]);
}
if (memcmp(sHeadFlag,sGpgs[1],5)==0)
{
GpgsaSol(&r_buf[r_out&0x7ff]);
atelliteLocked=Gpgsa.cSatInSolTol;
}
}
r_out++;
}
}
}

Your code is illegible because it's lost all its latout/formatting.
This is because you didn't follow the instruction about posting code.

Please follow the instructions on how to post code - it's right there immediately above the box where you type your message!
http://www.keil.com/forum/tips.asp

Once serial0Flag has been set to 1, your main loop will scan r_buf[] continuously without any synchronization to the incoming data and without checking whether it's looking at old data after wrapping.

I rewrite the source code as following:

//Serial ISR:
void serial0(void) interrupt 4
{
    ES0 = 0;
    if (TI0) TI0 =0;
    if (RI0)
    {
        r_buf[r_in&0x7ff]=SBUF0;
        RI0 = 0;
        r_in=r_in+1;
    }
    ES0 = 1;
}
//Main_Loop:
void main()
{
...
while(1)
{
    if ((r_in-r_out)>128)
    {
        serial0Flag = 1;
    }
    if(serial0Flag==1)
    {
        if (r_buf[r_out&0x7ff] =='$')
        {
            memcpy(sHeadFlag,&r_buf[(r_out+1)&0x7ff],5);
            if (memcmp(sHeadFlag,sGpgs[0],5)==0)
            {
                GpgsvSol(&r_buf[r_out&0x7ff]);
            }
            if (memcmp(sHeadFlag,sGpgs[1],5)==0)
            {
                GpgsaSol(&r_buf[r_out&0x7ff]);
                atelliteLocked=Gpgsa.cSatInSolTol;
            }
         }
     r_out++;
     }
}
}