Serial Full Duplex

Hi Community,
i have a big problem. I want to write something like a ECHO - Funktion. That means i recive a char an send it back like in this source ...

void serial_int (void) interrupt 4 using 3
{
    static char chr = '\0';

    if (RI == 1)
    {
        chr = SBUF;
        RI = 0;
        TI = 1;
            TL0 = 0xFF;
    }
    else if (TI == 1)
    {
        TI = 0;
        if (chr != '\0')
        {
            if (chr == '\r') chr = '\n';
            SBUF = chr;
            while(TI == 0);
            TL0 = 0xFF;
            chr = '\0';

        }

    }
}

The Problem is... i am using a Timer for multiplexing my LED-Digits.
Is there a faster methode for this application ?
(SRY FOR MY ENGLISH)