Issue with avr spi slave interrupt in proteus ATmega8

Question

I want to get some data from spi, but spi interrupt doesnt work. I get a message and a pause in proteus instead of a signal on LCD. How to fix this? My code:

void spi_init(){
    DDRB = (1<<PINB4); 
    SPCR |= (1<<SPIE) | (1<<SPE);
}

ISR(SPI_STC_vect)//
{
    str_lcd("            ");
    setpos(0,0);
    str_lcd("SPI"); //signal
    setpos(0,0);
}

int main(void)
{
    spi_init();
    sei();
    while(1){}
}

Answer 1

The data is not read out from SPI data register at all, so next transferred byte will overrun the first one. Also same thing happens if the LCD write is slow. In general, don't do slow things in an interrupt, only fast things you must do.